Radiator Fan Issue

[MikePGS]

Hello everyone. I don't really know much about cars, but I was hoping someone might be able to provide me with some insight to my problem. I have a 99 grand prix and it was having issues with overheating. I had my girlfriends friend's boyfriend (he's a mechanic) come over and take a look at it. He replaced a hose, and the thermometer. The fan wasn't coming on when it heated up so we replaced the temperature send switch. It still wasn't coming on when it warmed up so he rigged it so that the fan was constantly on. Unfortunately in this state I can't see the engine temperature, which is something I would like to see. Any idea as to what might be the trouble? Thanks in advance.

[BillBoost37]

Why can't you see the temperature? Remove whatever he did to have the fans always on and then check the below.

1. With a scan tool check the pcm temp vs the dash gauge temp
(Verifies the gauge is correct)
2. Turn on the ac, do the fans come on? They should
3. When the temp reaches 216F does a fan come on a slow speed, it should
4. At 228F the high speed fans come on, do they?

From there you are likely checking relays etc. If the pcm doesn't see the temp correctly, then it can't turn the fans on at the proper times. Overall it controls the ground to the relay for the fans.

[MikePGS]

Thank you for the information. I can't remember what he disengaged but I'll call him up later tonight to see what it was then use your method.

[fifty2pks]

what are the possible issues if the fans don't come on with the a/c?

[Scottydoggs]

most of the time if the fans dont come on with the a/c, the a/c dont work at all. as in no Freon in the system. if the compressor dont spin the fans wont come on.

you could also have bad wires to the temp sensor, or the new one was bad right out of the box, yes, it happens.

[goldgp]

correct me if im wrong bill, but if the pcm doesnt have any temp inputs, doesnt it defalt the fans to high?

[fifty2pks]

I think I'm having a similar issue. I just noticed it when I did a radiator flush. The fans won't kick on even after the temp gauge goes above the second needle when stopped in traffic. If I unplug the cts the fans turn on but of course then the temp gauge doesn't work. I'll be getting an obd2 bluetooth adaptor on Tuesday so I can compare the pcm temp to the dash gauge. If the A/C doesn't work so the fans won't kick on, is that related to the fans not turning on when the A/C isn't a factor?

I'm going to go over the A/C next for the summer but I'd like to revolve one issue before moving on to the next.

[fifty2pks]

Just tested my ac system for leaks. Good news is the compressor works and the fans kicked on when the compressor did. Bad news is I have a leak in my condensor. i just flushed the radiator so now I'm going to try and replace it without having to remove the radiator.