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TR6BILL
03-08-2009, 04:03 PM
Well, I got the throttle-actuator-solenoid gizmo all wired up and adjusted and it works! With one small problem. No matter where I wire it into my fan circuit, it won't disengaged as long as there is any current to it. Meaning, my fan, whenever it it turning (like when the car moves) will act as a generator and run electric current back to the battery. Even when the fan is off and it is slowing down to a stop, it is generating juice. Till it comes to a complete stop. Then the solenoid clicks off. Apparently, when this solenoid (from a TR8) senses any electricity, it stays on. Without getting into advanced electronics (diodes, etc.) my grand idea might well be an exercise in futility. I am so ticked. :madder:

Geo Hahn
03-08-2009, 04:32 PM
...Without getting into advanced electronics (diodes, etc.) my grand idea might well be an exercise in futility...

Quantum physics is advanced, "diodes, etc" are just fancy plumbing. I sure some (I can almost guess which someones) on the forum can solve this with a part from Radio Shack.

TRDejaVu
03-08-2009, 04:34 PM
Flux capacitor.

TR3driver
03-08-2009, 05:21 PM
Interesting. Must be a really sensitive solenoid, if the fan is generating enough current to hold it in.

What does your fan control circuit look like? Possibly the easiest solution is to power the solenoid from the same source that triggers the fan relay. Or if you don't have a fan relay, add one.

Driving the fan through a diode would also work, but is probably not the best solution because there will be some power wasted in the diode (meaning the fan will get less). Also going to take a major power diode to handle the fan's startup current; and likely a heat sink to deal with the heat from the wasted power.

TR3driver
03-08-2009, 05:22 PM
PS, is it just me, or has the BCF server been really cranky the last few days? It's taking me 2 or 3 tries for every post!

Doesn't seem to be my Inet connection, because everything else works fine.

Brosky
03-08-2009, 05:26 PM
It's not you alone Randall. My pipeline from the east coast is jammed at times too.

poolboy
03-08-2009, 05:29 PM
George had the answer a diode. I'm surprised they didn't supply one with the fan installation kit and relay.
It is installed in series and has a direction, in that it has to be installed considering the direction that the current flows.
This kit has a diode in the wiring.
https://cgi.ebay.com/ebaymotors/DERALE-FA...emZ330306874746 (https://cgi.ebay.com/ebaymotors/DERALE-FAN-THERMOSTAT-THREAD-IN-PROBE-SENSOR-KIT-16739_W0QQcmdZViewItemQQ_trksidZp1742Q2em153Q2el12 62QQcategoryZ33600QQihZ014QQitemZ330306874746)

Brosky
03-08-2009, 05:57 PM
That is the simplest solution Bill and you can solder it in in minutes. One quick trip to Radio Shack and you should be good to go.

TR6oldtimer
03-08-2009, 06:07 PM
Wow, wind power on a six! Surprising how rotating magnets and a coil makes electricity.

Get the inline diode, Radio Shack has them for from 1-3 dollars.

Brosky
03-08-2009, 06:16 PM
Ray,

I've got to brush off my electronics here before I say the wrong thing. Ray, help me out on this. If I read this problem correctly, there is a small amount of voltage feeding back through the circuit, causing the switch to engage when Bill doesn't need it engaged.

But that same circuit is needed to allow the proper amount of current to power the switch when he does need it, so it can't be totally disabled.

Then Bill would need to know the amount of voltage coming back, to allow him to get the least resistance possible to block it, but not enough to block everything, correct?

TR6BILL
03-08-2009, 06:49 PM
The fan sending back current to the battery (and my indicator light for my fan) is an issue that I called Dan Masters about some time back. He was the one that informed me that indeed I was actually charging my battery, in a sense, when I was driving. The fan indicator light actually glows at speed, telling me the fan is spinning from air current. And charging my battery. Cool.

Not so cool, a diode will block the current in the wrong direction. That is, no way to shut it down, even though it is a weak current from the fan turning. Indeed I have a really good relay (Spal, same as Brosky) that actually has a blank #87 post, but this does me no good, same circuit. The fan, when I turn it off, actually keeps the solenoid open until it comes to a complete stop, so the current has got to be weak, but enough to trigger the darn solenoid. Unless I bypass everything and do the switch-on-the-dash-with-an-indicator-light thing. But that sorta kills the automatic response I needed. Any other suggestions?

Brosky
03-08-2009, 07:14 PM
Bill,

Mine is wired to either run automatically, with no light on the indicator switch, or manually, overriding the temp switch/relay and causing the light on the manual dash switch to come on. I was not there the day that Erik wired mine in, so I don't know how he has it connected in the series of the harness.

I do not have any indicator light for the fan being on, except for the manual switch light.

poolboy
03-08-2009, 07:50 PM
Probably the simplest thing, albeit not the least expensive, would be to replace the fan with one that draws less current while stll putting out over 2000 CFM. They're out there.

poolboy
03-08-2009, 07:53 PM
Or activate the solenoid that you have with a manual cockpit switch when you need it at idle.

DrEntropy
03-08-2009, 08:34 PM
Okay.. we have "reverse" current from th' fan feeding back to the solenoid's coil... "diode" is the first thing popping into mind.

Bill, can you post a rough schematic as to how the fan/switch/light/solenoid are tied into the electrical system?

Brosky
03-08-2009, 08:41 PM
Doc,

Read my post and tell me if I was wrong. I think that he needs a diode that will have some resistance, but not too much one way, with total resistance the other. If he reads the voltage coming back when the fan is off, but back feeding the circuit, he can determine what spec diode he will need.

DrEntropy
03-08-2009, 08:56 PM
I did, Paul. My feeble reasoning agrees. A resistance at the "flow back" side should allow the diode to be a one way "gate" without a need for more rig. And: Yup! Measuring the "feedback" current as the fan freewheels when off will be the part to determine diode spec's. Tho I s'pose as speed increases (and th' fan freewheels faster) the feedback current will as well.

I'd be for the easy way out and lose the light and all that, wire the solenoid and fan to the same relay (or trigger device) and roll on. If ya just GOTTA have a light to say the fan's on, think LED. Ancillary to the END of the run.

71MKIV
03-09-2009, 09:02 AM
Allright, I just drew this out, let's try the KISS route first. If I could figure out how to post my drawing I would.

One way this is gonna work is to use a double pole relay, the solenoid goes on the second pole. This is the simpliest way of fixing this issue. Alternativly a second single pole relay would work, but to me that would clutter things.

The second way is with a diode. The diode would have to be installed after the relay, and after the connection to the solenoid. It has to be here, and now it's carrying all of the current of the fan. If I remember correctly, the fan draws on the order of 20 amps, so to have some room for heat, a 30 amp diode would be none too big, so Radio shack is out, they don't go that big, I just checked, you would have to use one of the big electronics suppliers, www.newark.com (https://www.newark.com), or www.digikey.com (https://www.digikey.com) to get a 30 amp 14 volt diode. You are also in the price range of a relay, 5 to 10 bucks.

One of the problems with this route is by the time you get a diode that big, you are into stud mounts and heat sinks with both sides of the heat sink being above ground electrically, which means that it needs to be isolated, no just fastening it to a handy piece of bracketry. Mounting it to the front of the fan might be an option, that way the air flow would keep it cool. I am assuming that it is a plastic fan and guard, no shorting issues.

Once a solenoid is pulled in you would be suprised at how little current is needed to keep them pulled in. On the order of milliamps.

Sorry to disappoint you Bill, but the fan isn't charging the battery, it's just lighting the light, there's no connection back to the battery with any of the switches being off. A diode in the line after the switch and indicator, heavy enough to carry the current of the fan, will prevent the light from coming on as the fan spins in the wind. Any diode in the line to the light, would keep the light off at all times.

Figuring out this kind of stuff is what I do for a living, so that's where I am coming from.

my money is on the two pole relay.

poolboy
03-09-2009, 09:40 AM
Steve, I've just been following this thread out of interest and learning some things, not that any of it applies to me, but would the double pole relay, prevent the spinning fan from activating Bill's high idle solenoid ?

71MKIV
03-09-2009, 10:28 AM
yes, a double pole relay is two seperate switches actuated by a solenoid. the "goesinta" can be wired together to the supply fuse, one switch turns the fan on, the other switch turns the rpm bumper upper on. When the temperature sensor satisfies, ie the engine gets cooler, it turns off, which turns the relay off, now the switches are open and there is no physical connection between the three circuits, the fan, the solenoid, and the relay coil. I can't figure out quickly how to post a drawing.

An inportant point to note: is that the spinning fan would not activate his solenoid, only keep it activated once it was turned on. The current requirments after activation are 1/10 what you need to activate. My original reading of the post is that his idle came up at first heat then stayed there until he stopped at a traffic light.
Hope this helps

TR6oldtimer
03-09-2009, 10:36 AM
Yep, the diode would only work if there was reverse current flow to the solenoid coil.

So, instead of attaching the idle solenoid coil to the contact side of the fan relay, connect it to the coil side.

71MKIV
03-09-2009, 10:43 AM
That would work. If you wired the solenoid so that it grounded through the engine temperature switch, the one that was used to turn on the fan relay, the solenoid would engerize with the relay, and be physically seperate from the fan circuit. You would wind up with the solenoid parallel with the relay coil.
Here's why I didn't go that route.
When the switch actuates the solenoid will draw a fair amount of current for a short time, known as a spike. When it turns off, what you have is a tiny ignition coil, that will also make an electrical spike. I don't know what kind of temp switch he is using, some of them will take these spikes happily and for a long time. some won't.
Putting the solenoid on a pole of the relay takes the temp switch out of the equation.

TR6oldtimer
03-09-2009, 11:00 AM
That would work. If you wired the solenoid so that it grounded through the engine temperature switch, the one that was used to turn on the fan relay, the solenoid would engerize with the relay, and be physically seperate from the fan circuit. You would wind up with the solenoid parallel with the relay coil.
Here's why I didn't go that route.
When the switch actuates the solenoid will draw a fair amount of current for a short time, known as a spike. When it turns off, what you have is a tiny ignition coil, that will also make an electrical spike. I don't know what kind of temp switch he is using, some of them will take these spikes happily and for a long time. some won't.
Putting the solenoid on a pole of the relay takes the temp switch out of the equation.



Now here is where a diode will work. Placed across the coil, it shunts current generated when the coil field collapses. Many relays and solenoids have shunt diodes built in.

poolboy
03-09-2009, 11:13 AM
An inportant point to note: is that the spinning fan would not activate his solenoid, only keep it activated once it was turned on. The current requirments after activation are 1/10 what you need to activate. My original reading of the post is that his idle came up at first heat then stayed there until he stopped at a traffic light.
Hope this helps

Thanks, Steve. That's my understanding, too. As long as the fan is spinning the "idle solenoid" remained activated, whether powered by the fan motor or just spinning from momentum.
Very interesting subject being discussed by you and the "oldtimer"; learning a lot. Thanks, guys.

TR6BILL
03-09-2009, 11:44 AM
Spal suggested not to use a diode. Lots of issues with the heat generated, the fact that it would have to be a pretty big diode (30 amp), etc. He suggested I hook up another relay to activate the solenoid. Here is where I get lost (I know nothing about electricity - I don't trust anything I can't see!). Where would I hook up the relay? From where I teed into my hot wire for the fan, the same wire that sends some juice back when the fan spins without power (like when it is cranking down, or spinning in the wind, creating these little milliamps which keep my solenoid open?). Now, if I have a single relay wired here (knowing little or nothing about what the relay really does) (I want to keep my Spal relay in place, made for the fan - waterproof, etc.)what keeps the relay from, for lack of a better word, "relaying" with these milliamps coming at it. Or does it need a full 12 volts to jolt it open, or whatever a relay does. This would mean I would need a separate, independent source of power for the actual solenoid? And the juice from the fan would only serve to "open" the relay?

Isn't this fun? If I show up to the N.O. show with a dummy solenoid, I will get razzed.

71MKIV
03-09-2009, 11:44 AM
[/quote]

Now here is where a diode will work. Placed across the coil, it shunts current generated when the coil field collapses. Many relays and solenoids have shunt diodes built in. [/quote]

yep, and a tiny diode at that.

TR6BILL
03-09-2009, 12:18 PM
Uh, I am still hanging here.... :crazyeyes:

71MKIV
03-09-2009, 12:53 PM
Sorry Bill, If you were to live next door, we could have this sorted in under a half hour.
Look at your new solenoid. There's a little arm that pushes on the throttle, if you were to take that arm, and have it push a little toggle switch instead of your throttle, you would have a relay.

Let's try something here for the sake of simplicity and go with what Ray said.

Take a wire from the hot wire on the car side of your fan relay, and go to one wire of your solenoid.

I hope your solenoid has two wires on it, because the second one then goes to the wire on your fan relay that goes to your temperature switch.

If you wire things in this way, your solenoid will then be controlled by your temperature switch, and it will last long enough for me to mail you a drawing, or for me to figure out how to post a drawing.

Does that make a little more sense?

71MKIV
03-09-2009, 12:57 PM
Just went back and checked, the picture shows two connections, your golden, the above scenario will work.

swift6
03-09-2009, 12:59 PM
Just out of curiosity, have you checked wiring diagrams for AC/Automatic equipped TR7s to see what the factory did? Though it looks like it was wired into the AC compressor so it wouldn't get residual electrical feedback from freewheeling.

BTW, That solenoid was never used on TR8s, not from what I can see anyway. It doesn't appear anywhere in the TR8 manuals that I have, my factory AC equipped carbed TR8 has no such device either and the FI cars would not need it. It does appear in TR7 manuals for AC and Automatic equipped carbed cars. Its referred to as a "Throttle Jack".

If you need, I can scan and post the wiring diagrams showing it.

TR3driver
03-09-2009, 01:03 PM
Uh, I am still hanging here.... :crazyeyes: Bill, you've already had several solutions offered that will work. I'd offer more, but I don't know how you are controlling the fan, and it makes a difference.

71MKIV
03-09-2009, 01:37 PM
Um, Randall?
My understanding is that he wasn't referring to the original issue of the fan acting like a generator.

Your idea of the diodes out of an alternator is a supply of them I had not thought of. Next time i'm at a upullitt I will have to remedy the situation

TR3driver
03-09-2009, 01:43 PM
My understanding is that he wasn't referring to the original issue of the fan acting like a generator.Oops, you're right. My mistake, didn't read enough of the thread.

poolboy
03-09-2009, 03:07 PM
Sorry Bill, If you were to live next door, we could have this sorted in under a half hour.
Look at your new solenoid. There's a little arm that pushes on the throttle, if you were to take that arm, and have it push a little toggle switch instead of your throttle, you would have a relay.

Let's try something here for the sake of simplicity and go with what Ray said.

Take a wire from the hot wire on the car side of your fan relay, and go to one wire of your solenoid.

I hope your solenoid has two wires on it, because the second one then goes to the wire on your fan relay that goes to your temperature switch.

If you wire things in this way, your solenoid will then be controlled by your temperature switch, and it will last long enough for me to mail you a drawing, or for me to figure out how to post a drawing.

Does that make a little more sense?



Steve, I'm assuming if Bill wires it up that way, the solonoid won't be activated if he turns the fan on with his manual over ride switch ?

Brosky
03-09-2009, 03:09 PM
Gotta love this forum. All this help and advice in a day? Imagine doing this 10 years ago.

Triumph Restorer Wanna-Be's

Go to the BCF first for guidance

DO NOT enter the garage without it

poolboy
03-09-2009, 03:21 PM
:iagree: I know if it weren't for having these resources (people) , I'd be stumbling around with a lot of my projects.
And, probably more importantly, if you do mess up, there's always somebody that can get you out of the mess.

TR6oldtimer
03-09-2009, 03:54 PM
I agree, I have spent to many years trying to do this.

https://attheridge.files.wordpress.com/2008/12/square-peg-round-hole.jpg

TR3driver
03-09-2009, 04:16 PM
Steve, I'm assuming if Bill wires it up that way, the solonoid won't be activated if he turns the fan on with his manual over ride switch ? If the override activates the relay, then with that setup it should activate the solenoid, too.

Brosky
03-09-2009, 04:51 PM
Ray,

The problem is not the peg and hole.

Your hammer is obviously not big enough for the job.


NEXT PROBLEM!!!!

TR6BILL
03-09-2009, 06:07 PM
My Spal fan is controlled by a Spal relay, which is pretty much a standard relay. Hot in and hot out, with a ground and a tickler wire to the Spal temp sensor. I also set up a dead short wire to a switch on the dash to ground out the sensor to override manually. With indicator light. I wired the solenoid with a ground wire to the body and the hot wire to the same hot wire that feeds the fan, after the relay. Therein lies my problem. The little bit of juice fed back through this wire is enough to keep the solenoid open until there is zero juice coming in, ie, the fan is motionless.

TR3driver
03-09-2009, 06:44 PM
Ok, so three choices. Take your pick :

1) Wire the solenoid in parallel with the relay coil. If there isn't already a diode on the relay or solenoid, add one, so no question of inductive kickback damaging the temp sensor. Easy, quick, this would be my choice (but I have diodes laying around so don't have to drive to Radio Shaft).

2) Add a relay for the solenoid, with it's coil in parallel with the existing relay. You could still add shunt diodes if you want, but the relay contacts should be big enough to deal with the solenoid without the diode.

3) Find a double pole relay and use it to replace the existing fan relay. This is the most elegant solution, but I don't know of an easy source for a double pole relay. The starter relay from a 74-75 TR6 is double pole, but I don't know if it's coil is rated for continous duty or not.

Brosky
03-09-2009, 07:07 PM
Illustrated examples are here: Relays explained (https://www.bcae1.com/relays.htm#demo)

DNK
03-09-2009, 07:09 PM
Ya know Bill, just stick the stock fan back on and call it good. :devilgrin:

TR6BILL
03-09-2009, 07:25 PM
Ya know Bill, just stick the stock fan back on and call it good. :devilgrin:

Your arse......

TR6BILL
03-09-2009, 07:27 PM
I think I am getting a headache.

Brosky
03-09-2009, 07:32 PM
Better than a tooth ache.

You can take an aspirin easily enough. Harder to drill and fill your own cavity.

TR6BILL
03-09-2009, 07:44 PM
You can take an aspirin easily enough. Harder to drill and fill your own cavity.

I've done that. Not easy. Takes a steady hand. :crazyeyes:

Brosky
03-09-2009, 08:08 PM
I'm getting queasy just thinking about it.....

71MKIV
03-10-2009, 05:27 AM
My Spal fan is controlled by a Spal relay, which is pretty much a standard relay. Hot in and hot out, with a ground and a tickler wire to the Spal temp sensor. I also set up a dead short wire to a switch on the dash to ground out the sensor to override manually. With indicator light. I wired the solenoid with a ground wire to the body and the hot wire to the same hot wire that feeds the fan, after the relay. Therein lies my problem. The little bit of juice fed back through this wire is enough to keep the solenoid open until there is zero juice coming in, ie, the fan is motionless.



awright, I'm back. Couldn't get a keystroke in edgewise on the computer last night.

Bill, simple, take the wire that goes from the relay to your solenoid off the hot wire after the relay, and put it on the hot wire BEFORE the relay.
Then take the other wire from the solenoid and put it on the wire that goes from your temp sensor to your switch.
All will be well.

71MKIV
03-10-2009, 07:46 AM
For some reason I am having and interesting time posting a picture. Dunno why.

I will get this figured out yet, the same way I always have, by pushing buttons until something significant happens.

I have a screen shot saved as a jpeg of a pdf file I scanned of a drawing I made of Bill's bumper upper wiring.

I am just having trouble getting it to display.

71MKIV
03-10-2009, 07:49 AM
https://lh5.ggpht.com/_KifeITs1KJE/SbZfERLNw3I/AAAAAAAAAD4/gC0jT_dI0so/s144/Adobe%20Reader%20-%20%5BDOC031009.pdf%5D%203102009%2081541%20AM.bmp. jpg

well, there it is, if anybody can make it big enough to see, be my guest.

70herald
03-10-2009, 04:45 PM
<span style="font-weight: bold">Ok, so three choices. Take your pick :

1) Wire the solenoid in parallel with the relay coil. If there isn't already a diode on the relay or solenoid, add one, so no question of inductive kickback damaging the temp sensor. Easy, quick, this would be my choice (but I have diodes laying around so don't have to drive to Radio Shaft).
</span>


Bill this is the simplest, best solution. Just hook the solenoid up directly to the thermostat or the COIL side of the relay and everything will work.
No need to worry about the temp sensor, they will handle way more current than what the solenoid will ever draw.

TR6BILL
03-10-2009, 05:47 PM
https://lh5.ggpht.com/_KifeITs1KJE/SbZfERLNw3I/AAAAAAAAAD4/gC0jT_dI0so/s144/Adobe%20Reader%20-%20%5BDOC031009.pdf%5D%203102009%2081541%20AM.bmp. jpg

well, there it is, if anybody can make it big enough to see, be my guest.


G_d bless you Steve. That said, I CANNOT READ YOUR DIAGRAM! I tried blowing it up and it all came out fuzzy, unreadable. And thanks everyone for the spirited help. I may sound like the Village Idiot, but can someone spell it out in kindergarten terminology for me? I will make a run Friday to the marine electrical shop for a good relay and some good wire. Got plenty of bullet connectors. Really, really want this to work. Hang with me. V.I.

TR3driver
03-10-2009, 06:21 PM
Two wires from the solenoid, right? One goes to the hot wire to the relay; the other goes to the wire from the relay to the temp sensor and dash override switch.

Sorry, I have to run, or I'd redraw Steve's diagram for you.

DrEntropy
03-10-2009, 07:42 PM
I've currently got ONE good eye and a lot of angst and frustration. No way to diagram the circuit.

I like the two-in-one relay solution best.

Brosky
03-10-2009, 08:09 PM
Sorry Bill, I can't make it out enough to redraw it either. It's too small to blow up.

71MKIV
03-10-2009, 08:33 PM
Mumble mumble, I'm at the wrong computer too. I'll be at the right one tomorrow morning. I'm going to try something. Bill, Watch for PM

71MKIV
03-11-2009, 12:20 PM
Bill, I sent you the link to the actual drawing by pm. Did you get it?

DNK
03-11-2009, 12:29 PM
Probably still cleaning up the eggs off the fridge

TR6BILL
03-11-2009, 07:57 PM
Got it Steve. Sitting on my work bench, waiting for Friday (my day off) when I can go to the marine electric store to get some good wire and shrink tubing.

On another approach, a buddy gave me a <span style="font-weight: bold">diode</span> (he has a towing service and drag races a Chevy II [made PINKS]). We ran it across a 12 volt field and it passed all the juice through one way and blocked all the juice the other way. Hmmmm. Just an inline setup. Confusing myself.

poolboy
03-11-2009, 08:03 PM
Bet you're glad Don won't be at Delgado.

DrEntropy
03-11-2009, 08:13 PM
Got it Steve. Sitting on my work bench, waiting for Friday (my day off) when I can go to the marine electric store to get some good wire and shrink tubing.

On another approach, a buddy gave me a <span style="font-weight: bold">diode</span> (he has a towing service and drag races a Chevy II [made PINKS]). We ran it across a 12 volt field and it passed all the juice through one way and blocked all the juice the other way. Hmmmm. Just an inline setup. Confusing myself.


Ya can try it, not much to lose. And a simple two splice trial as well. My bet is: it'll work.

71MKIV
03-12-2009, 05:53 AM
Here's what you have to do, that diode would have to go in the circuit at the fan, let the air flow over it to keep it cool. The drawback to that is that if it fails, the fan don't run, not even with his manual override switch. To get to the car show this weekend I suggest not going down unknown roads, and just wire it like on the drawing. Next week we can play.

TR6BILL
03-12-2009, 05:54 AM
Will do.

71MKIV
03-12-2009, 05:55 AM
ps, can you post a picture of the diode?

Brosky
03-12-2009, 07:23 AM
How about a better picture of the diagram.

71MKIV
03-12-2009, 07:30 AM
https://picasaweb.google.com/starspanglers/ScreenCaptures#5311537337464636274

DrEntropy
03-12-2009, 08:22 AM
Should work fine as Steve's setup. :thumbsup:

DNK
03-12-2009, 10:10 AM
Bumper Upper?????? :jester:

71MKIV
03-12-2009, 12:33 PM
Iputsomuchcaminmyenginesoitrunsreallywellbutitdoes n'thaveanybottomend
andIputareallybigfanonittomakesureitstayscoolbutit won'tletitidlesoIhad
toputsomethingonittomakeitidlefaster. :crazyeyes:

bumper upper was easier to say.

DrEntropy
03-12-2009, 01:35 PM
mehheh!

Not to mention all th' pencil lead you save!!! :laugh:

TR6BILL
03-12-2009, 06:42 PM
ps, can you post a picture of the diode?
https://i2.photobucket.com/albums/y17/billkaram/diode.jpg
A big sucker. Can carry 40 amps.

Brosky
03-12-2009, 07:01 PM
That thing looks like a transmission mount..........

Is this for your fan or the transformer on the pole outside your house???

Just kidding...good luck.

TR3driver
03-12-2009, 07:55 PM
Might be big enough; but don't forget it will need a substantial heat sink for continuous operation. Also don't forget that the mounting stud is hot, so it needs to be insulated from the car body/chassis.

TR3driver
03-12-2009, 07:55 PM
Oh yeah, and your fan will turn slower, due to the voltage drop across the diode. Not much, but some.

71MKIV
03-13-2009, 05:36 AM
It will be big enough, and the fan won't turn noticeably slower. Mounting is going to be the challenge.

I have heatsinks in amongst my junque pile that will work.

Mount it at the fan, so the airflow will keep it cool. And rewire the bypass switch so that the switch bypasses the diode, an "awcrap get me home" kind of thing.

This calls for some experiments and an infared thermometer.

To me that's next week, and another thread. :wink:

TR6BILL
03-13-2009, 07:58 AM
The electronics store guy said I shouldn't need a heat sink, especially if I mount it in the way of the breeze created by the fan. Also, I thought about putting some short pigtails on each end of the diode, with soldered bullet connectors (British Wiring type) and sorta insert it in the wire, with enough slack that I could pull the diode if it fails and simple insert a length of wire inline. Again, MacGiver-style. The guy that sold it to me said I might lose a fraction of a volt capabilities at most, impedance?

71MKIV
03-13-2009, 08:19 AM
Well, your running at half its capacity, so maybe you wouldn't need a heatsink. The only way to find out for sure is to plug it in and find out. Putting wires on it with bullet connectors would work, and a piece of wire in the road repair toolbox.

Like I said, I would put it out front with the fan, with the diode in the breeze.

What the heck, whatcha got to lose?