chevyc4man

I have a 94 lt1 I recently purchased. I have noticed that the cooling fan is always on. Even when I start it cold. The temp gauge is right in the middle 190-200. Is this a problem? Bad thermostat? Harmful the Vette? Car is running fine. Any suggestions are appreciated!

AaronDoud

My Camaro was doing that last winter and it was a bad thermostat. Would guess the same here.

chevyc4man

Another tidbit, it does not run when the ignition is in the on position, starts as soon as the engine is turned over. Thanks again!

kerrynewman

The previous owner probably by passed the temp sending unit for the fan so the fan is always "on". Allot of people do this because their car is running hot. This "procedure" does not fix the problem, just masks it.

Does Your car run hot? As one of the replies above, check thermostat, clean out the area infront of the radiator (You might be surprised what you find),flush out the radiator fins, and if that does not fix an overheating issue, you may need a new radiator... assuming your water pump is good, no leeks around the water pump? A 94 has an 18 year old rad, yep you better replace it, I would, cheap insurance.

Plus if your fan is "hot wired", it probaly shuts off when you turn the key off, right? The fan should keep running if the car has just been driven hard and engine is hot. If the fan shuts off after key off, the engine gets hotter and hotter for a while... not good.

That's my 2 cents, You'll get plenty of ideas here, this is a great forum, cheers!

chevyc4man

The car is not running hot. I have only put about 500 miles on the car and don't remember the fan running before this week. Bought from a big Chevy dealer and it has a 3 month 3,000 mile warranty so I guess I can have them check it out. I don't think anything has been re wired. The fan is not running when I shut it off, but I think that is because the temp is only about 190?

C4boy

If it wasn't modified as Kerry mentioned, I would look in the area of a bad cooling fan relay. If the fan is on, it's an electrical issue. Something is triggering the fan to stay on when it shouldn't be.

kimmer

It could be in limp mode.

desertmike1

Time for a FSM & DVOM

by the way...94 fans are controlled by the ECM/PCM not a thermostat switch, but by information sent to the processor from the ECT probe.

And just imagine...most of us complain we don't get enough fan cooling time

84VetteMan205hp

my 84 does that the fan turns on when i turn the key to the on position and stays on until i turn the car off. doesn't run hot ether

chevyc4man

Had the car looked at. PCM needs replaced. They told me part comes from gm and will take 4-6 weeks to get? Seems odd.

Manibusj

This describes how my 95 LT1 is setup... another mod was the Engine Coolant Temp Sensor was intentionally left unplugged. Any reason why the techs would do this? I'm going to try and plug it in along with your recommendations, but I don't know if there is more to this mod that I need to correct.

Thanks!
Jerome

Paul Workman

New ECM??? Hmmmm.... Maybe, but...

Grounding the fan relays: It was a common solution to a problem that didn't exist: The LT1/4 (as well as most modern cars) run in the temp range you are seeing, by design. Your coolant temps appear to be normal, assuming stock configuration. No problem with the temps: Normal for that motor.

Typically, the first fan would come on around 200-205 and the second wouldn't come on until approximately 230 was reached, OR the A/C was turned on, which signaled both fans ON. (A trick to keeping the temp cooler is to turn the A/C on, believe it or not!)

Look and see if there is a wire running from the the fan relay harness to a chassis ground; a dead give-away someone "fixed" the cooling problem (that didn't exist). (A better check would be to disconnect the harness from the relay and the ECM and "ohm" the signal wire to ground. Zero or near it would indicate the relay will be ON anytime power is applied to the HOT side of the relay coil.)

NOW... if you WANT to run cooler, then a cooler thermostat will get ya there. Looks like the fans are already running anyway, so you'd be all set.

Manibusj

This is a great explanation, thanks for sharing this info. I'll inspect the fan relay harness. So just curious, other than a piece of mind, sinec this mod is common, should I even bother chasing it down and getting the cooling system back to stock configuration?

Paul Workman

Well, you have options:

1. Do nothing. The only down side is maybe a little more wear and tear on the fan motors; the second fan in particular. But, considering one fan runs most of the time anyway, we're not talking about a major concern here.
   
2. Back to stock: Fix the "always on" situation, and do nothing else.
   
3. Reprogram fan control: A custom calibration (chip) could be installed to control when both fans come on. (I like the 205º point my chip is programmed for. This works really well (for me) as the motor comes up to temp and stops right there, even in summer heat. (Stock radiator too) And, I have more head-room before it gets to the 260+ range.)
   
4. Install a lower temp 'stat': Provided there is "enough air" flowing, the coolant will stabilize at the temp the thermostat opens. However, if there is less than enough air to maintain coolant temp at the (e.g., 170º) lower opening temp, a larger radiator and/or fans coming on at the lower temp will be needed.

Manibusj

Paul, thanks again for your advice...I really appreciate it! I did find where they modified the wiring harness because there were 2 wires that were grounded together and lots of electrical tape. I'm going to mull on the different options you gave me and go from there.

Manibusj

Hello everyone,

Sorry for the delayed update...I was in the middle of resealing the intake manifold due to a leak and then replaced the injectors due to a leaky injector. Now that I buttoned everything up, the only thing I have left is the cooling issue. So I bought a new coolant temp sensor and plugged it in. Amazingly, this fixes one code and it also fixes the issue of a hard warm start...however, only the primary fan comes on at 228. Any ideas if this is normal and if/when the secondary fan should come on? More than likely, I'll buy a cooler thermostat, but wondering if the mod is preventing the second fan from coming on when it should.

Thanks,
Jerome

ricasso

My 94 did this a while ago, it turned out to be the MAF sensor..fitted a new sensor, problem solved!

Paul Workman

I'm guessing the relays both work, b/c grounding their coils is what triggered them "on" in the first place.

Ordinarily the second fan relay is not triggered by the ECM until temps reach at least 235-8º ish. However, you can just turn the A/C on and the second fan should come on as well. IF NOT, then the secondary fan relay is NOT being grounded by the ECM. Wringing out the connections and the wire harness would be easy enough to do. Then see that the appropriate pin on the ECM is grounding with the A/C switched ON.

NOTE: Do NOT push the standard volt meter probe into the cylinder of the pin and cylinder ECM (or any) connector. The cylinder may be over stretched and fail to spring back to normally make contact with the pin side of the connector, resulting in an open circuit at the connector after the harness is plugged back in.

Manibusj

Paul,

Thanks again, will do on the connections. As for the AC, that's another issue that I'm working. The clutch bearing is going out, so I try not to turn that on. I'm in the process of ordering a new clutch bearing...then hopefully there are no leaks and I can just recharge the system.

Jerome

Paul Workman

Well, as I recall from my 95 LT1 Vette, the connector for the compressor clutch is on top and easy to get to. Un-plug it and then you can switch on the A/C long enough to see if both fans come on. Easy pleasy...

P.