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Tips

It works....with one caveat. Dang.

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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.
 
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.
 
71MKIV said:
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.
Click to expand...

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.
 
71MKIV said:
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
Click to expand...
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.
 
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.
 
[/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.
 
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?
 
Just went back and checked, the picture shows two connections, your golden, the above scenario will work.
 
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.
 
TR6BILL said:
Uh, I am still hanging here.... :crazyeyes:
Click to expand...
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.
 
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
 
71MKIV said:
My understanding is that he wasn't referring to the original issue of the fan acting like a generator.
Click to expand...
Oops, you're right. My mistake, didn't read enough of the thread.
 
71MKIV said:
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?
Click to expand...
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 ?
 
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
 
: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.
 
I agree, I have spent to many years trying to do this.

square-peg-round-hole.jpg
 
poolboy said:
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 ?
Click to expand...
If the override activates the relay, then with that setup it should activate the solenoid, too.
 
Ray,

The problem is not the peg and hole.

Your hammer is obviously not big enough for the job.


NEXT PROBLEM!!!!
 
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.
 
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