When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Your 93 doesn’t have “high speed” and “low speed” modes. That requires three relays and was not implemented until mid-94 model year. A 93 only has two relays, one to turn on fan #1 (typically at 226°F in stock program), and then fan #2 at 235°F. The Overview of the switch you linked only discusses high and low speeds, not individual fan on/off. Might need to clarify that with the vendor.
My suggestion would be to sort out why they aren't turning on at the programmed temps. Is the chip in the ECM stock? When you switch the dash panel **** to A/C can you actually see the compressor operating, but fan #1 does not turn on? Does fan #1 come on at 226°F without the A/C? Does your engine even get that warm? Your resistance on the temp sensor was a bit off (high) at 180°F. Best check is to put it in boiling water (212°F assuming you are located at sea level = 177 ohms).
I am not sure about the temps, I don't have a SCAN tool and investing in one seems a bit steep. Far as I know the motor is bone stock, the cats were deleted under the previous owner so not sure if that effects anything? I have not checked the temp gauge sensor in the head yet but I am pretty sure that it works, the motor gets pretty hot based on feeling when the hood is opened.
Dumb question, how can I tell the AC compressor is operating? See below photo & caption. AC Compressor. Is the facing supposed to turn when the AC is on? If so, it is not. However, when I turn the ac the rpm drops for a sec, but it doesn't feel like their is cold air coming out of the vents. According to shbox, the system needs to be charged for this to come on, so maybe I just need to charge the system? But even so according to shbox's site the fans should still come on when the motor gets hot enough.
What temp does the dash gauge show? Not necessarily the same precision as the ECM circuit, but it might indicate the temp is way above or way below the fan actuation temps. That would give a crude determination if “the engine is hot enough”. The resistance reading for 180°F may be indicating the temp sensor in the water pump is not accurate.
If you have a laptop, Scan9495 (also works on 93) will allow you read the codes, ECM data, reset codes, log the ECM while the car is being driven, etc. Software is free, you buy a cable. The author (GaryDoug) is a member here and can help with any install or operating issues. If you are serious about maintaining your LT1 and optimizing it's reliability and performance, a scanner is a good investment.
I let the gauge get up to the below highlighted marks before I shut it off, the fan still does not turn on at this point which should be hot enough for them to turn on:
Thanks for the support and help. I will look into getting Scan9495! I may just buy a replacement ACDelco coolant temp sensor and see if that does the trick, its only about $50 and easy to replace.
The 1993 coolant temp gauge is misleading, because is appears to be mislabeled. It shows 100° as the lower hash mark, while all subsequent years show 160°. This has led a lot of people to claim the 93’s run a lot cooler than later years. They don’t.
If you linearly interpolate the hash marks for the later years, the middle mark is 210° as clearly shown on the Firebird gauge. The 3/4 mark works out to 235°F. Your yellow mark would correspond to 217°, not enough to turn on fan #1. As it went above the yellow mark fan #1 should have turned on. The red mark is right in the break point between fan #2 turning on, so it might not have reached the turn on point. And the dash gauge is not as accurate as the reading sent to the PCM since it is single wire and relies on battery voltage (variable) and quality of ground, while the 2-wire sensor in the water pump housing is supplied with a more precise, regulated 5 volt power supply in the ECM.
You can get a genuine OEM sensor from discount GM parts dealer for. $33. AC Delco is similar quality, costs even less.
Injuneer thank you for the gauge info! Turns out the fans are coming on after all, just took it for a test drive and the primary fan came on right about where you said it would (just past the yellow) and it cooled right down. Guess I just freaked out, but I swear it got up to the red (in the gauge itself) the other week and the fan didn't turn on. Maybe my mind was just playing tricks on me.
I will definitely keep an eye on it going forward tho. I'm going to chalk the gauge up to a 1st model year quirk!
From: Born on the Florida West Coast, now where can I retire?
Re: Fans are not working?
I kinda know how you feel. I am a big worrier about my cars. When I see the temp gauge going up with no fans on, I tend to panic even though I really know they do not come on until a specific temperature.
I know I'm way behind on this fan issue you guy were talking about a few months ago, but I have a 94 Z28 also and I'm having the same issue's with the cooling fans not coming on. I've changed the temp Sensor thinking it was the problem and that didn't fix it. Unplug the MAF Sensor and both fans come on. Did anybody ever figure out what the issue was?
I know I'm way behind on this fan issue you guy were talking about a few months ago, but I have a 94 Z28 also and I'm having the same issue's with the cooling fans not coming on. I've changed the temp Sensor thinking it was the problem and that didn't fix it. Unplug the MAF Sensor and both fans come on. Did anybody ever figure out what the issue was?
Are these the “same issues” described by the original poster in post #1, or the “same issues” described in the newer post #14?
What testing have you done, other than unplugging the MAF?
Are these the “same issues” described by the original poster in post #1, or the “same issues” described in the newer post #14?
What testing have you done, other than unplugging the MAF?
Ok, my 94 started running hot, and I checked the fans and they were not running, at that point I let it cool off, did a little research, and found the thread that said if you unplug the MAF sensor and the fans come on then you probably have a temp sensor issue. The sensor was cheap so I decided to replace it and see if that worked. It did for about 25 miles and then, same thing started running hot again and the fans were not working. So the fans do seem to work for short periods of time and then the issue happens again. Do you think it could be a sticking thermostat?
Last edited by Tim114975; Jan 20, 2023 at 05:56 PM.
What are the actual temperatures you are seeing when it’s “running hot”? Are you basing the coolant temp on the dash gauge or the value seen by the PCM?
A temperature sensor circuit can be faulty because of the sensor or the wiring/reference voltage. Both the circuit for the dash gauge/single wire sensor in the head and the circuit for the PCM feed/2-wire sensor in the water pump need to be verified.
I’m just basing it on the dash gauge and I can smell the coolant getting hot. I’m going to do some more checking on the wires and voltage. I’ve just found the service manual online which will help a lot. I will also check this article out and try and verify that I have the correct voltage. I do not have a PCM code reader, might see if I can borrow one, so hopefully I can track down faulty wires.
The next hash mark to the right is 235°F, past that on your 1994 the gauge shows red. In 1995 the Camaro gauge was modified so that 1/2 of that space was no longer red. That would put the red starting at about 247°F. There are no significant differences between the 94 and 95 engines and cooling systems.
GM designed the engine to run at 210°F. That yielded the best combination of emissions and fuel mileage.
What I still need to know is what is the temperature on the dash gauge when you feel the engine is “running warm”? Some people seem to feel that anything past the midpoint of the gauge is too hot. That’s not really the case. We can infer from the lower fan turn on temp that GM does not see any problem as long as the temp is below 226°F.
I have a late production 1994 with three fan relays, usually the temp gauge hand stays around a quarter or what I think is 180 degree or 200 degree, the car has been sitting in a garage for more than two years and I've just recently tried to get it running. New Battery, Starter and now a temp sensor. I never remember it going past the half mark but I may be wrong. Driving it now and the temp stays down around 200, but getting back home idling in the drive and the gauge goes up three quarters getting very close to the red. I've also had a Freon leak in the A/C and I've just added some freon into the system. I've been reading that that may have played a part in it also.
