First of all, many thanks for all the technical documents on the site. They've helped me along, but I'm still stuck. 1996 3.8L
My radiator fans won't run under normal heating conditions, so when idling my car's temperature increases until it overheats.

I've applied direct 12V to the fans -- they operate.
I've tested all the fan relays against the fog lights -- all of them operate the fog lights..
I've tried starting the car without the ECT plugged in, and the fans run.
I've replaced the ECT sensor and watched the temperatures with an OBD scan tool. When the temperatures got to 85C/185F, fans do not turn on.
I've also tried pulling the PCM battery fuse for a few minutes as suggested by someone online.
Also, the engine temperature is fine as long as the car is moving 35-40mph or more.
And the compressor for the AC is completely dead, but still on the car, if that could cause any problems.

I'm all out of ideas, my car won't run the fans and I don't know why.

 

What "overheat" temperature is the gauge getting to?
185F? Keep waiting. The fans aren't commanded to turn on until engine temperature gets to the 221F range.
In the heat of summer, seeing the temp gauge hit 230 isn't uncommon.
So now, is your engine really overheating?

 

I had read that the fans were supposed to kick on low at 184F, and I was using that as a reference.
I drove it once in 90-95 degree weather a couple months ago and the gauge on the dash almost pegged, so I just parked it until I had time to work with it.
What is the highest temperature that the engine is safe to run at? Thinking that it was going to just blow if left to idle, I haven't actually let it go that far again since I started working on it.

And thanks, I have no idea what I'm doing.

 

Safely? Believe it or not, depends on the type of oil you use. Dino oil will break down way faster at high temps vs synthetic, usually in the 240 range. 50/50 water/coolant will boil at 285 degrees with a 15 lbs of pressure in the system. I'd say 230-235 is safe for a short period of time. My Jeep runs at 210 whether I'm on the highway or idling and weather is 0 degrees out or 100 degrees.

 

It looks like I didn't do enough testing after I got the new ECT sensor put in. It's kicking the fans on at 221 and never getting any hotter than that now. I got some misinformation about expected temperatures and didn't let it go that far until today but everything's fine now.

Also, since it looks like idle temperature is going to hold here, could I ask about engine oil? I just have what the manual recommends in it, it's at 175k miles. Any reason to change?

 

Stick with the recommended grade of oil, no reason to change from that. High mileage oil is best since you're wayyy passed 75k miles. Don't worry that it says part synthetic and don't let people scare you from synthetic oil. Most of the people that steer away from synthetic know absolutely nothing about it and only believe rumors of what they heard.
Enjoy if you want to read.

https://camaroforums.com/forum/loung...ing-oil-73773/

 

yes synthetic oils are great for high milage cars ,once i move to synthetic i dont go back ,thats what they recommend ,i ussally think about that after about 100.000 miles ,it does not break down near as fast as conventional oils do ,but if not burning any oil ,your good like said

 

Idk who is recommending you that, but they are wrong! Another rumor that people believe...going to synthetic and then you can't go back! HAH! You can switch back and forth without issues. Buy 2.5 quarts of each if you want and mix it, you can even use two different brands. You won't hurt anything.

 

it is important that you get all the air out of the cooling system.