Temp guage not working, fan always on. - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums

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post #1 of 8 (permalink) Old 09-15-2013, 11:37 PM Thread Starter
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Temp guage not working, fan always on.

So I just finished yesterday doing my head gasket and after about a 3 months of off and on maintenance, the baby fired up on the first try!! Ha so that was the highlight of my weekend.

Anyway along the way of getting the heads milled and cleaned, the machine shop broke the temp sensor on the driver side head (I probably should have removed it anyway)

So as part of putting everything together I bought a new one, and for some reason the connector didnt plug in so I took a look at the pins and noticed it should have fit because it had two pins just like the old one that broke and was even the same shape but didnt plug in. So I cut the connection and took it to Oreilys and bought one that if fit into, thinking it would work just fine.

Once installed and once I ran the car, first thing I noticed the fan came on as soon as it fired up, not only that the temp guage didnt work at all!!

I let the car run for a few minutes and same thing, no movement of the gauge, so I was wondering where I could start to trouble shoot the issue?

This was never a problem before the head gasket replacement and the gauge worked just fine, I checked the fuses and everything looked fine, any help would be appreciated!!
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post #2 of 8 (permalink) Old 09-16-2013, 06:25 AM
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Coolant temp gauge sender for 95 should have just 1 wire which is dark green. It's the cts for the pcm that has 2 wires. Cts for pcm is in water pump.

Test of gauge involves unplugging dark green wire with ignition on, gauge should read cold.

Then ground the dark green wire, gauge will read hot.

Last edited by cocobolo95; 09-16-2013 at 06:32 AM.
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post #3 of 8 (permalink) Old 09-16-2013, 09:49 AM
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You should have gone to a dealer or ACDelco supplier and gotten the correct sensor. Parts houses are well known for not having the correct temp sensor for the head.

Now, the temp sensor in the head would have nothing to do with your fans coming on. Is your check engine light on? The fans will come on when it is. If so, scan to see what trouble code is indicated.
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post #4 of 8 (permalink) Old 09-16-2013, 06:11 PM Thread Starter
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Alright thanks to your guys quick responses, I was able to determine that the gauge is actually good, once it was grounded it pegged past hot! I guess just because the connector plugs into the part doesnt mean its the right one. I did notice that the gauge rests at a normal low position when the ignition is off and the wire is plugged into the sensor, but once I turn the ignition on it goes below that normal level, as if it was unplugged.

All in all im more than sure that for some reason its the sensor, I searched for the ACdelco part # at the part store and it gave me a result to a part that wasnt automatically generated by the people at the store, so Im going to give it a shot, only 13 dollars.

About the fan always being on, only the "Service Engines Soon" light is on, so when my cable comes in Ill be able to scan for codes. Any this else I can do to isolate the fan problem? I mean I really don't care if the fan is always on so long as I can gauge works but I actually want to keep this car as original as possible, any other ideas or suggestions would be appreciated.
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post #5 of 8 (permalink) Old 09-16-2013, 06:28 PM
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If the ses light is in, the fans will run. Nothing you can do about that except unplug them. Once whatever is setting off the trouble code is correcred, the fans will resume normal on/off operation controlled by the ecm.

Correct the sensor & check trouble codes.

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post #6 of 8 (permalink) Old 09-16-2013, 08:58 PM
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You don't have a fan problem as already stated. The fans are on because of the check engine light.
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post #7 of 8 (permalink) Old 09-18-2013, 08:43 AM Thread Starter
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Alright guys so yesterday I was able to finally drive the car from my base to my apartments knowing the temp gauge worked.

Turns out the sensor was the right one and did work, but because the fans were coming on as soon as the car was started, and it has no T-Stat installed, it was just keeping it extremely cold to the point where I assumed it wasnt working.

The way I was able to determine this was pretty much I had to unplug the fan and let the car idle for about 10 minutes, when I saw the gauge move, I then realized this.

Thanks for all your help, Im waiting my OBD1 cable to arrive so I can see what codes come out, and for now im going to try to see what I can do to get the Speedo and Odometer working, apparently some Jack@$$ never wired them right during the automatic to manual swap so thats what im dealing with.

For now im enjoying the car and my gauge problem is solved!
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post #8 of 8 (permalink) Old 09-18-2013, 12:11 PM
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Put a thermostat in it. It's important for the reverse flow system to function properly.
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