I'v read most of the posts on here about electric cooling fan problems. I have tried everything and trouble-shooted. My question is, could the computer in my 92 RS be the problem. Also my hydrocarbons caused me to fail my emission test. Since I have hooked a switch to the cooling fan to trun it on, is it possible my engine (305 TBI) is not getting hot enough to burn off the hydrocarbons? One more thing, I have found a good website for used and new camaro parts if anyone is interested in. Its www.perrypam.com. Thanks for any help. Scott.

 

Tried everything? Have you scanned for error codes? Entering KOEO Field Service Mode will cause the fan to run, and would be a valid test of the ECM output to the fan relay.

Another way to test the ECM output is to disconnect the A/C high pressure line pressure switch, which should also operate the fan relay immediately (ignition ON, of course).

 

I have scanned for error codes. I did get a code 42, which I know is not related to the cooling fan. The only way I can get the fan to work is either turning on the AC or flipping the switch I installed that I hooked into the fan relay. I went through the troubleshooting section of my chilton manual and every test was OK. Thats why I was wondering if the computer could be bad. Maybe the part that deals with the cooling fan is not working. I replaced all the sensors, and relays, and checked all the wiring between everything, it all works. Thanks for any help. Scott

 

I unplugged the AC high pressure switch with key on and the fan did not come on.

 

Are you certain you had the correct A/C pressure switch?

It no longer matters, since you've just provided the key piece of evidence. You stated that the fan WILL operate if the A/C is turned on. That means that the ECM IS in fact operating the fan relay output, so the ECM hardware and firmware is intact.



That indicates to me that the ECM is not getting an adequately low signal from the CTS that would require it to operate the fan. I would suspect that the CTS and dash temperature gauge are not in perfect agreement. That dash gauge may be indicating a higher temperature, and/or the CTS may not be perfectly calibrated.

Another consideration is the temperature at which you presume the fan should operate. The typical stock fan turn-on temperature is around 223°F indicated coolant temperature. If the CTS is not reporting that temperature or above, the ECM will not operate the fan without the A/C request.

One thing you can do to test this is to install a 100 ohm resistor in place of the CTS and start the engine. The ECM should operate the fan as soon as the engine is running.



If there are other points of resistance in the CTS circuit, such as from poor connections. they will only lower the indicated coolant temperature to the ECM, and add to the problem.

Incidentally, the HC level is not normally raised by a higher coolant temperature. NOx emissions tend to increase at higher combustion chamber temperatures, but HCs tend to reduce in a hotter engine.

 

since he has an L03 (single fan setup), it is controlled by the fan switch located on the passenger head, between #6 & #8 spark plugs. try grounding the green/white stripe wire coming off the fan switch. the fan should come on unless the fan motor, fan relay, or fan power supply is faulty.

 

Thanks for the correction. I completely ignored the "TBI" thing. A Freudian phenomenon, I believe...

 

I grounded-out the wire to the fan coolant temp switch on the passenger side above the starter. When I grounded it the fan came on, so I replaced the CTS. When the engine warmed up the fan did not come on. Later on when I tried to restart my car my TBI is flooding so bad the car won't start and I have a code 15. If the new CTS is bad would it send a signal to the computer to dump more fuel in the TBI? Thanks for any help. Scott

 

ok. did you replace the radiator fan switch? if not the fan will still cease to function. on your system it is controlled by the switch and not the ecm as in mutli-port models.

 

I don't think so. Were is that located? I replaced the one on the P/S above the starter, the one on the D/S, and the one on the intake manifold in the front. Also replaced the relays.

 

if you replaced it with a stock one, the stock one dosn't turn on the fan till around 238* HOT!

yes i believe you replace the correct one on the p/s.

the one on the top, front is called the CTS (coolant temperture sensor). a bad one could cause the engine to flood. ie it's telling the computer the engine temperture is -30F and it's not. that will flood a warm/hot engine short order.

 

The engine temp got up to almost the red line before a manualy turned the fan on. I'll try replacing the other and see if that corrects the flooding problem. Thanks.

 

it could be that the new fan switch is bad. especially when shopping @ autozone. i would recommend a TFS8 it will turn on the fan @ 205* which maybe appear on a stock gauge closer to the 220* mark. stock gauges are inaccurate. i would recommend buying ac delco parts or the borg warner brand. wells i would stay away from like the plague.

 

I think your right. After work today I'm going to the chevy dealer for GM stuff and see if that fixes it. Thanks for all the help. Scott

 

Transporter,

I apologize if I got you started in the wrong direction. Good thing the Mystik caught my error. He's all over this one. The sensor in the left head is just that - A sensor. It varies resistance based on temperature, and operates the dash gauge. The sensor in the front of the intake is the same, and reports to the ECM.

The temperature switch in the right head is a SWITCH. It merely changes state from off to on at a specified temperature. Make sure you replaced the switch with a switch, and not with an analog resistive sensor.

While the Mysik is right about using better components for more critical applications, like the TPS, ignition parts, and other critical sensors, for something as simple as a thermal switch, Wells or any other replacement brand is probably just fine.

The one exception would be the MAF, since Wells is apparently the only aftermarketer to offer a thick film sensor for our cars. However, that doesn't apply to your TBI.

This is no time to give up. You've already done all the diagnosis, so visiting the dealer is just redundant work. Since grounding the dark green/white wire operates the fan, the only thing left is the switch. As mystikkal suggested, get a lower temperature switch, and make sure the sealant you apply to the threads still allows the sensor body to ground itself to the head. I'd suggest a paste type thread sealer instead of PTFE tape.

 

Thanks for all the help. Will ry to fix it today. Only bad thing so far was I had to drive my sons Ford Focus to work (big wing on back, body kit, skinny tires and dark window tint). It sucked.