C4. cooling fan question

[Dale P.]

I bought my wife a 92 LT1 for her to drive (versus my 68 427).. I noticed the other day that BOTH cooling fans are always running even when the car is started on a cool morning .. my first thought was to be sure that the a/c was off so I checked and it was off ... I left the engine run and watched the analog gage temp rise to 210F and also watched the digital reading from the ECM .. that digital reading never moved off of 0 F . and neither did the oil temp, yet that analog gage for the oil temp worked fine too ..... so something is common to both systems and is bad/faulted giving bad readings to the ECM .......... I am assuming that this is why both fans are running .. I verifed that the service engine soon light at least lights up .. and it does ..there are no codes stored since the "SES" goes out after start up ... or is that a bad assumption? ...... that is why my level of understanding C4s end .... any suggestions??

[Terry M.]

Re: C4. cooling fan question

Dale my experience is with Gen II LT1s in B-bodies, but I suspect the Y-body will be similar. The engine coolant temperature sensor to the ECM is in the water pump, toward the driver's side. Check that the connector (2 wires on the B-body, but it might be 3-wires on the Y-body) is connected, and the contacts are good. If it is connected and contacts look clean and tight consider replacing the sensor. You will have to drain the coolant low enough to get the level below the sensor in order to change it.

There can be codes stored even if the SES light is currently not on. I believe a previous code will be stored for something like 40 ignition cycles. You will have to check a service manual to determine if a stored code can be extracted without a scan tool. I know for 1994 and newer one needs a scan tool, but some earlier (I just don't know how much earlier) systems will release the stored code without a scan tool. One will need a service manual to find what the code, if there is one stored, means and to find a troubleshooting tree to diagnose it anyway, so add the appropriate service manual to your library.