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Any way to bump up my RPMs when fan comes on?

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Yeah, I went to the spec sheet and saw that, Bill. I bet it does a number on the headlights too.
I guess I shouldn't doubt their figures, because you are definitly noticing the effects of the amp draw.
I know that Spal is a good product, but considering how little it comes on, maybe something like this would have less complications, while putting out sufficient cfm's.
https://cgi.ebay.com/ebaymotors/PROCOMP-1...sspagenameZWDVW
BTW Northcoast is another source for ZDDP; scroll down the ad.
 
BobbyD said:
Bill............which Spal fan do you have? I've got their 16" low profile puller which draws 3.8-4.2 amps per their spec sheet. However, the 16" high performance puller draws between 21 & 23.5 amps. That's a huge difference but in poking through the Spal site, it appears to be correct. At least I now know why I see no RPM impact when the fan kicks in! :driving:
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How about I hook up my Hurricane Katrina Honda Generator in my trunk? :crazyeyes:
 
Bill, where did you get the fan, steal in from some swap buggy???
clan_fan_boat.jpg
 
First, I don't think it is the radiator fan that is the problem, but the heater fan. I can turn on the heater fan and watch my Amp gauge swing to the left and I have a 96 amp alternator.

Next thing, the TR7s had a jacking solenoid to hold the idle up when the A/C was turned on. Maybe you could install one of those to raise the idle when the system kicks on.

jclay
 
jclay said:
First, I don't think it is the radiator fan that is the problem, but the heater fan. I can turn on the heater fan and watch my Amp gauge swing to the left and I have a 96 amp alternator.
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That's th' motor needing service or replacement. Lube in the bushings has turned to rock... or corrosion has encroached.

jclay said:
Next thing, the TR7s had a jacking solenoid to hold the idle up when the A/C was turned on. Maybe you could install one of those to raise the idle when the system kicks on.
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...I'm turnin' blue here...
 
DrEntropy said:
That's th' motor needing service or replacement. Lube in the bushings has turned to rock... or corrosion has encroached.
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I'm inclined to agree, but ... isn't there a fuse in the fan circuit? Seems like it should pop the fuse if it's drawing more than 20 amps or so, which I would expect the alternator to keep up with.

Of course it may be that the alternator just doesn't have <span style="font-weight: bold">any </span>excess capacity at idle. Amp ratings are always peak output, the actual output falls off dramatically at lower rpm. The actual curve varies with the particular alternator, but this one for example is rated at 100 amps, but only produces about 15 amps at 1500 rpm (at the alternator).
 
Doc;

Blue may become your new fav color!
I agree with you, put in a solenoid and "VOILA"!!!!!

Dave :savewave:

P.S. Always heed the advice of the Doctor!
 
DrEntropy said:
Alternator draw is the first WAG. Look into "A/C idle compensator solenoids". Mebbe you can MacGyver one to the throttle linkage.
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I went to NAPA today to inquire about above such device and they threw me out! I will keep trying to research the darn thing. MacGyver, huh.
 
Okay, another option, and easier to wire in, is a "delta" design alternator. The kind that the emergency vehicles use. Designed to give near full output at idle or just above idle.

I think Brosky went to this design. That way the alternator will be working without the draw which is dropping the idle down. Way to verify if this is actually what is happening. Ampmeter hooked up. Watch what the output is at idle, turn the fan on and see what goes on. IF the ampmeter reads minus then you know there is a draw that will put more load on the engine, lowering the idle speed.

Those little idle solenoids are all over the place. GM used them on their carburetors throughout the 80's.. Thing is to figure out how to wire them when to get voltage...
 
TR6BILL said:
I went to NAPA today to inquire about above such device and they threw me out!
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Well, I was going to suggest this as a starting point, but then I saw the price! Mebbe you could find one in the junkyard tho. Unfortunately I didn't think to save it, but the car went to it's grave with the original solenoid still on there (and 250,000 on the clock), so they do last a long time.
 
RonMacPherson said:
That way the alternator will be working without the draw which is dropping the idle down.
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Doesn't solve the problem. Even a delta-wound alternator still takes power to turn in proportion to it's electrical load (that pesky 1st law of thermodynamics), and Bill's problem would not appear to be low voltage at idle. <div class="ubbcode-block"><div class="ubbcode-header">Quote:] Thing is to figure out how to wire them when to get voltage... [/QUOTE]That should be easy, just power the solenoid from the same switched source that the fan uses. Fan comes on, solenoid activates. But that means you need a solenoid that is powerful enough to oppose the throttle spring ... as I recall the one I linked to above was not strong enough to open the throttle on it's own. It would only hold the throttle up once I tapped the gas.
 
They must have misunderstood you at NAPA, sahib. You must march right back up to that counter and make sure the dummy understands that you want a 5/16 throw solenoid for a Triumph TR6 with triple Zenith-Stromberg 175 CD carbs.
You gotta be clear about what you want with some of those guys.
And if he still doesn't get it, take your business to O'Reillys.
 
TR6BILL said:
DrEntropy said:
Alternator draw is the first WAG. Look into "A/C idle compensator solenoids". Mebbe you can MacGyver one to the throttle linkage.
Click to expand...

I went to NAPA today to inquire about above such device and they threw me out! I will keep trying to research the darn thing. MacGyver, huh.
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Try a shop which specializes in air conditioner repair. Particularly one with employees old enough to remember what a carb is.
 
Just got off the phone with Spal and described my problem. He said my alternator is not putting out its maximum amperage at low rpm, and the fan is sucking way past list amps at startup, then settles down to 22 amps. Still, at low RPM for the engine, it is sucking down the alternator and straining the engine, thus bogging the idle down 200. The only thing hotrodders do is to go with a really high output alternator, he suggested the GM unit from a 96-2000 Bonneville 3.8 engine. This monster puts out 200 AMPs! Over 100 at idle. He said that would solve my problem. I looked it up, this baby needs a <span style="font-weight: bold">4 gauge wire</span> to the battery. My current Delco-style alternator is on 73 amps, and he said way less than that at low rpm. Any comments??
 
Seems like exactly the wrong solution to me, but I could be mistaken.

No matter how big or small the alternator, how much power it takes to turn it depends (mostly) on how much power it is putting out at the moment. With no load, the battery voltage rises until regulator shuts down the armature current and the armature spins freely (except for the drag of bearings, brushes, wind resistance, belt friction etc.) When an electrical load, such as your fan, is applied, the regulator senses the drop in voltage and applies current to the armature, which makes it suddenly much more difficult to turn.

I've seen this first-hand, on my little homemade alternator test stand. With just a washing machine motor to turn the alternator, it has no trouble at all generating 14.4 volts with only a small load (test lamp). But adding two headlight bulbs puts the motor under a noticeable strain, and four will stall it. Four headlight bulbs is roughly 20 amps, same as your fan.

If your engine is bogging down because it cannot supply the extra power to turn the alternator, then a bigger alternator isn't going to help.

But if the problem is that the battery voltage is dropping until the ignition doesn't work right, then a bigger alternator (or possibly even just a smaller pulley for your current alternator) would help.
 
Oh BTW, I agree with your Spal rep; the fan will draw considerably more than it's rated current for several seconds after power is applied. But the alternator need not supply this extra current, in a well designed system the battery should have no trouble picking up the difference. This is basically what happens at idle, with the stock alternator and the headlights on. Once you leave the stoplight, the alternator recharges the power taken out of the battery.
 
poolboy said:
They must have misunderstood you at NAPA, sahib. You must march right back up to that counter and make sure the dummy understands that you want a 5/16 throw solenoid for a Triumph TR6 with triple Zenith-Stromberg 175 CD carbs.
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PB...I know two NAPA stores up in Maine that would know exactly what you were talking about. They're both owned by a guy named Patton :jester:
 
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