a fully charged automobile battery can be as high as 12.75 volts. the 12 volt figure is just nominal.

the open circuit voltage put out by the alternator, can approach 15 volts.

when the alternator voltage is applied across the battery terminals, the alternator is in parallel with the battery, so the resulting voltage is somewhere in between. the the alternator feeds the loads, while charging the battery. the loads see only one voltage source, assuming that the cables are properly sized, so their parasitic voltage drop is negligible.

so with the alternator charging, you read voltage somewhere between the battery stand alone voltage & the alternator open circuit voltage. after the engine shuts down, you read the battery voltage only.

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On my ass, as usual.

glad to hear that plugging in the water temp sensor helped... it made a huge difference for me too in terms of idle.

for the fan, did you have the fan switch points changed? IIRC the stock fan turns on at a really high temperature (210 or 230?) depending on if the car is in AC mode or not. what color/pin# did you tap into for your fan relay signal?

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http://www.cardomain.com/ride/641869 < Step by Step LT1 FC swap Documentation & Pics

http://www.cardomain.com/ride/2801662 < Step by Step LS1 FD swap Documentation & Pics

For relay terminals 85 & 86, I grounded one, and connected the other to PCM Connector #2 (green) pin 33 (remember, I've got a 2004 GTO harness). I'm re-thinking this... should I have used a 12v source instead of a ground?

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If you can't fix it with a hammer, you have an electrical problem.

I think the PCM grounds the 12v to complete the circuit. I think you need a 12v sources feeding 85 and 86 going to the PCM so it can get grounded.

Someone smarter will confirm or deny.

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1993 Mazda RX7- Did you bring enough?

fused 12V source to 30, pcm to 86, ground to 85, replace the lights with your fan in the following pic:



from: Hook Up Driving Lights (wiring)

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It will be a great day when our schools have all the money they need
and the government has to hold a bake sale to buy another bomb.

Craig, does your relay have one 87 terminal or two (87a, 87b) terminals? If two, see the N.O & N.C. descriptions in the link above.

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It will be a great day when our schools have all the money they need
and the government has to hold a bake sale to buy another bomb.

"N.O. and N.C."... couldn't begin to tell you what that means...

I have four prongs on the 70 amp relay... Initially, I connected 86 to ground (as was depicted in the Painless drawing)... Then, forum members told me that 86 was supposed to be connected to 12v switched, so I changed it. Neither way works, so I'm pretty confused. Either way, I still have 85 running to the PCM trigger.

I think I have 30 and 87 wired correctly, and understand that these are interchangeable ("like a road which can go either way"), so I think my problem is with 85 & 86.

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If you can't fix it with a hammer, you have an electrical problem.

Somebody mentioned about the air intake sensor.
Had a similar problem b4, it was the air blowing from the radiator
fan directly to the sensor.
It could be the cooling fan blowing directly to the air filter.

I just made a heat shield for it.
Hope this would help.

Yea it made a huge difference on mine too, so huge it made my car not run without it hooked up...

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93 LS1 7

I'm good on the idle now...that's fixed. Now I need to figure out why the fan won't come on, even though I'm positive the fan works...
Also, Danzan's recommendation to test the battery voltage stopped vs. running was excellent; it's 12V both ways, so my alternator is either not working, or the connections are loose.

__________________
If you can't fix it with a hammer, you have an electrical problem.