LT1-LT4 Modifications 1993-97 Gen II Small Block V8

overheating/fan problem... help

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Old Jul 24, 2009 | 01:46 AM
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Default overheating/fan problem... help

been trying to finish the camaro up. we changed the timing cover to a 97 before knowing I could just tune it out. but when we went to take it for a test drive the fans weren't kicking on and it overheated a little and turned off and wouldn't start ( i guess a safety feature ) well we've been trying to figure out the problems with the fans, but everything is fine.. all the wiring is continuous, no grounding/shorting problems and is getting 11.8 volts to the relay.

tried switching relays around, but nothing worked. if you take the relay out and jump the 2 wires together, the fans will turn on.

any ideas?

if the car is on and the a/c is on max cold, the low speed fan will always be on right?
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Old Jul 24, 2009 | 02:41 AM
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you should get high speed fans with AC on, also about the car shutting off...mine has never overheated but a buddy of mine has a 96 that overheats daily and his has never shut off on him??? Its warped a set of heads but never shut off
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Old Jul 24, 2009 | 04:47 AM
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Make sure the coolant temperature sensor in the water pump is connected. If it is, the sensor may be faulty.
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Old Jul 24, 2009 | 07:49 AM
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Mine had that problem, the PCM stopped sending the signal to the Relays to turn the Fans on. A friend of mine just had the same problem a couple weeks ago, we had his on a Scanner and the Sensor was giving accurate temperature.

I don't know if yours is this problem..I'm wondering more what causes it.
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Old Jul 24, 2009 | 01:08 PM
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Originally Posted by the_merv
Mine had that problem, the PCM stopped sending the signal to the Relays to turn the Fans on. A friend of mine just had the same problem a couple weeks ago, we had his on a Scanner and the Sensor was giving accurate temperature.

I don't know if yours is this problem..I'm wondering more what causes it.
yeah, we were doing the scanner also, and the temperature was reading about 212 when the gauge on the dash was reading like 240.


The cts is plugged in and reading... in the cooling system it looks like it's almost all coated in rust.. it's all brown on the inside, and won't come off, could that be a problem? ( the block sat for a month or so before it was put in)


they have a 97 trans am too, would it be worth switching the computer from the t/a to the camaro to see if it might be the computer.. do they interchange?

no fans are turning on when the car is on and a/c is on. i don't think the cts could do that could it?

Last edited by realitygt; Jul 24, 2009 at 01:14 PM.
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Old Jul 24, 2009 | 01:44 PM
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Check the Fan Fuse first, then try switching the PCM.
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Old Jul 24, 2009 | 01:47 PM
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Originally Posted by the_merv
Check the Fan Fuse first, then try switching the PCM.
fuse is fine, it's not blow or anything. will the t/a computer work?
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Old Jul 24, 2009 | 01:50 PM
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Yea, try it and see what it does.
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Old Jul 24, 2009 | 02:16 PM
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I'll try it around 5:00 and report back.
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Old Jul 24, 2009 | 02:41 PM
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Roger.
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Old Jul 24, 2009 | 03:00 PM
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I believe if you jumper the # 5 and 6 pins (from the top left) in the OBDII plug it should trigger the fans to come on. If they do then the computer has the ability to turn them on, if they do not then it doesn't. If that doesn't turn them on then disconnect the plug on the pass fender, the one with more wires in it, closer to the engine and send a ground to the dark blue for high speed and the green for low speed. Ground a test wire and just touch it to the pins in the harness (the unpluged harness, the half closer to the front of the car, not the half going back to the computer). If these turn the fans on then the relays and other wiring is definately good.

I just had this issue with mine and flushing the system with fresh water and replacing the thermostat fixed it. I also had some cut up wiring under the fuse box that I had to fix. The fans wouldn't come on at all when I got the car, now they work fine, even with the manual fan switch I installed turned off.
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Old Jul 24, 2009 | 03:52 PM
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Originally Posted by slow96z
I believe if you jumper the # 5 and 6 pins (from the top left) in the OBDII plug it should trigger the fans to come on. If they do then the computer has the ability to turn them on, if they do not then it doesn't. If that doesn't turn them on then disconnect the plug on the pass fender, the one with more wires in it, closer to the engine and send a ground to the dark blue for high speed and the green for low speed. Ground a test wire and just touch it to the pins in the harness (the unpluged harness, the half closer to the front of the car, not the half going back to the computer). If these turn the fans on then the relays and other wiring is definately good.

I just had this issue with mine and flushing the system with fresh water and replacing the thermostat fixed it. I also had some cut up wiring under the fuse box that I had to fix. The fans wouldn't come on at all when I got the car, now they work fine, even with the manual fan switch I installed turned off.
when we jumped pins 5 and 6, nothing turned on.
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Old Jul 24, 2009 | 03:56 PM
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Then I believe you are correct in your computer diagnosis. Pull the ECM fuse and let it sit for 30 minutes or so and see if it will reset. I think the software might have some sort of "shunt" built into it that turns off the fan circuit in the event of a short or something. Try letting the computer reset and then jump them over again. If that doesn't work then try it with a new computer.

Did you try grounding the wires I talked about to make sure they work? If there is a short somewhere in that circuit then it might tell the computer not to turn them on again. Make sure they work right before you do anything else.
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Old Jul 25, 2009 | 12:20 AM
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couldn't switch the computers out tonight, but i'm letting the ecm fuse sit out w/ battery disconnected overnight. I'll see what happens in the morning.
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Old Jul 26, 2009 | 10:33 PM
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Any update? Just wondering have same problem I just leave the relay jumped and fan runs all the time with the key on. Would be nice to get it fixed right.
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Old Jul 26, 2009 | 10:41 PM
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^^Install Manual Fan Switches bro.. I had to do the same with mine and did it to a friends car, and about to do it to another person's car I know cause of the same reason..
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Old Jul 27, 2009 | 12:50 AM
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thinking about installing the manual fan switches, but i just want to know why it's doing it anyway..

at idle it says timing is at 32* that sounds way too high, and it's also showing a MAF code again, we have three MAF's that all work fine.. one in the t/a, one in the camaro, and one in a work van.

the idle is still at about 1100 rpms. searched the entire car for anything wrong and the only thing was a split transmission cooler wire..

Last edited by realitygt; Jul 27, 2009 at 02:32 PM.
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Old Jul 27, 2009 | 07:59 AM
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What is the MAF code that it's showing?
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Old Jul 27, 2009 | 12:44 PM
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Mines also giving the maf code don't remember which one tried switching it out with my buddys maf off his 94 camaro reset the computer and as soon as I started the car back up the code came right back. Wonder if I need a new ecm. on a side note my car runs crazy rich i've been thinking that has to do with the maf code I get? Thanks for the tip about the manual fan switches Merv. After I get my funds for my rebuild I'll do that. But the car is hardly ever driven right now because I'm to embarrassed from all the smoke.

Last edited by Dundee1; Jul 27, 2009 at 05:45 PM.
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Old Jul 27, 2009 | 02:31 PM
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maf or vaf a ckt malfunction p0100 is the code.
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