It's been a while since I've posted here. I've had my 95 since 99. It's completely stock and original. 65k on the odometer. I've been having an overheating problem just recently. Car will overheat if not moving. My fans are kicking on when the ac is on and the car will not overheat even while not moving. AC off and the temps will continue to climb into the danger zone. Both analog and digital temp guages are very close in their readings (analog is a bit higher). Did a coolant change about 5 years ago (and no, I did not remove the knock sensors and do it thoroughly as I should have). I'm lucky if I've driven it 5 times since then. Can't recall if that's when the skyrocketing temps started or not. I'm mechanically inclined but I know to "stay in my lane". Any help on where to start would be helpful and appreciated. Thanks.

 

Check for debris between the radiator and a/c condenser.

 

Two easy items to check:

1) As noted, check and clean the radiator and condenser. Its like a big vacuum cleaner. Check the pictures below, this is from my 1992, when I pulled it apart to do my LS swap. (I hadn't had the car too long, I assume this was there when I bought it). This was running fine with typical LT1 temperatures when driven.

2) With it idling with the AC off, have you verified that both fans are actually coming on at the correct temps and spinning?

 

If the engine is not overheating with the a/c on and the fans running, then it's not a blocked or clogged radiator.

First thing first: figure out if the fans are running when the a/c is off.

Second thing second: what temps are you considering "overheating?" On a stock 96, the fans aren't programmed to turn on until coolant temp reaches 219F (Fan 1) and 228F (Fan 2). The only temp gauge that matters is the digital one that shows up in the DIC. That's the accurate one, and it's the one the PCM reads. The PCM is what decides when the fans come on.

Below is the schematic for the fans on a 96. I would expect your 95 to be identical, including the PCM pins. From a quick glance, I don't see anything downstream of the PCM that would allow the fans to come on with a/c but fail to turn on when coolant gets above the reference temps. IOW, if the fans work with a/c on, then the wiring, relays, and motors are good and the only thing preventing them from coming on is the PCM not signaling them (as far as I can tell). If they aren't coming on at the coolant reference temps, then probe the two PCM outputs to see if it's actually sending the signal to the relays. If it's not, then there's some other reason the PCM doesn't think they should turn on, and you'll have to diagnose that.

 

Radiator is spotless. It'll hit 245/250 and neither of the fans are running. I'll then turn on the AC, fans kick on, and things cool down. Is there a sensor that tells the pcm to kick on the fans? Fuses?

 

There are two coolant sensors. One is in the passenger-side cylinder head and just runs the "analog" gauge in your dash. It is pointless. The other is up in the water pump area and feeds the PCM (which then feeds your digital readout. The PCM gets its coolant temp info from that sensor. But if that sensor is bad, the car usually runs badly. I'm sure there is a way to test the voltage on that sensor line, but it sounds like it's feeding your DIC good temp info. You can easily probe the two PCM outputs (see diagram) to see if they ever send voltage to the fan relays. If they are sending voltage for the a/c, though, then they should also be doing it for the temps. I really can't think of why the fans would come on for a/c but not the temp.