As the subject says... 20 degrees this morning. Turn key to run. Whats that noise? Why the hell is the fan on??? This happens every now and then. The car runs very cool so I know it wasn't on when I shut it down the night before. And no the A/C wasn't switched on. Any ideas? Also, I have cold idle probs. It idles pretty high and slowly comes down as it warms up. IAC is new and passages are clean. CTS was supposedly replaced as well.... it looks new.. but could it be 'bad' from factory? Thanks for all input.

Patrick DeGrosse Jr.

 

Are you using the defroster?

The AC compressor is wired through the defrost curcuit. This is so the air blown onto the window is moisture free. When AC high side pressure increases, the fans cut in.

When you notice your fans on like that, look to see if the AC clutch is engaged. It should cycle on and off.

 

A/C is gone... removed that is. The compressor is still there but all wires are disconnected. The fan will still kick on when I turn the switch to A/C though. Yet at the time this happened I made sure that the controls were set to OFF. Any other ideas? And Thnx for these quick responces.

Patrick DeGrosse Jr.

 

Bad fan relay, shorted wire, bad fan switch on engine. There could be more things to check for so you'll have to eliminate them one by one.

Steve

 

BTW: It is SUPPOSED to idle high when cold. It's to help it warm up faster.

Just so you know... There is a dark green wire that goes from the a/c selector switch directly to the fan relay. So it doesn't matter if the a/c is there or not, if you move the lever to A/C, bi/lev, or defrost, it'll turn on the fan.

There is also a wire from a pressure switch in one of the A/C lines to the fan relay. Should also be dark green. It's possible that when you removed the A/C stuff you cut this wire and it's grounded somewhere (GROUNDING this wire causes the relay to turn on the fan).

The computer should also turn the fan on, it's possible (but I think pretty unlikely) that your computer is confused. This would probably be from a bad CTS (coolant temp sensor).

And finally, there is a backup coolant temp sensor that also turns the fan on. On my car it's on the passenger side between plugs 6 and 8 I think. This is simply a temperature activated switch that grounds another dark green wire to turn on the fan relay. On my car, at some point, the end of the wire that connects to this sensor touched the exhaust manifold and melted and became useless. So I tucked it out of the way and rigged a manual fan switch. If yours is also melted and disconnected, it's possible the wire is hanging around and happens to be touching a metal part
(grounding, and turning on the fan). Mine did that occasionally until I tucked it out of the way.

The fan relay will only work when the car is on, however, so even if you have a short somewhere you don't need to worry about the fan coming on while the car is parked and draining your battery.

 

Okay so I have some sensors to check. As for the high idle.... I'm talking high.. like 2500. And when I say it needs time to warm up.. I mean like 20 mins. During this time the idle will slowly fall and eventually, when warm, it still idles at a high 1000 to 1100 rpm. Would a bad CTS do this? If not, what else should I look for. As I said, IAC is clean and working fine and I set it according to the tech section. As I was setting it though I could not get the motor to idle below like 800 with the IAC disconnected. It would just sputter and stall out. I noticed that the injectors don't spray the cleanest pattern in the world either.... would that cause any of these idle symptoms? As for the fan.. i'm not real worried about it, its just kinda wierd I guess. Anyway, thnx for all the input thus far... nice to know I can count on you guys to narrow down problems.

Patrick DeGrosse Jr.

 

Perhaps a vacuum leak? Check and make sure a hose isn't disconnected somewhere. A bad CTS shouldn't cause that sort of problem.

What kind of engine do you have?

You shouldn't have any trouble getting it to idle below 800 rpm... I can get mine to idle as low as 400 (although it's a little rough). A bad spray pattern from the injectors could cause rough running and general slightly sub-optimal performance but I doubt it would cause a high idle. I'd guess vacuum leak for my top suspicion. That would explain the high idle when setting the IAC.

Does the computer throw any codes?

 

Its a TBI 305. No codes. How should i check for a vaccuum leak? Does that propane test really work? Or is the stethoscope a better method. I'm gonna get a couple new injectors in this week and see if that solves it. I can't think of anything else that would do it though.. thnx for trying though.

Patrick DeGrosse Jr.

 

btt

 

I'd hold off on spending the money for new injectors just yet if I were you. I have a 89 with TBI also. When mine had a really bad spray pattern coming out of the injectors, I was going to buy new ones for mine too. It was drizzling out in big drops instead of a nice fine mist. I came to find out that TBI injectors rarely, if ever, go bad. What it turned out to be on mine was the o-rings that go around the top and the bottom of the injectors were worn out, causing fuel to leak past the injectors instead of being pressurized and sprayed through them like its supposed to. I think I paid about 30 bucks at Napa for a rebuild kit that came with the o-rings, new injector screens, and all the necessary gaskets for the whole throttle body. So make sure your o-rings aren't just shot before you buy new injectors, it's quite a bit cheaper of a fix.

 

Thanks.. I guess I'll try that first