Help me with these questions if you can:

I know there are two fans. One runs while the AC is running and the other is the primary cooling fan. Shouldn't the primary fan run during engine operation and after the engine is shut off until the water temp cools. I noticed that the engine temp climbs unless either the car is moving or the AC is turned on. With the AC on it will stay between 200 and 215 at idle. When I shut the engine off, I can hear the overflow bottle "gurgling". I seem to recall hearing the fan running for a short time after I turned the engine off. I don't think it is running at all right now.....hard to see.

 

If you have 2 fans (not all cars do). Main fan comes on around 226-228* or when AC is on. Aux. fan comes on around 236-238 (if you have it). If you turn the engine off with the key to the off position the fan will not run.

 

From the 1994 C4 FSM

Fan 1 will come on if
ECT about 219 degrees
Engine oil temperature above 261 degrees
A/C head pressure above 189 psi

Fan 2 will come on if
ECT about 228 degrees
Engine oil temperature above 277 degrees
A/C head pressure above 225 psi

 

'87 non a/c specs are 226 Main and 228 Aux (the Aux should rarely if ever come on). Or with the a/c, the Main Fan is driven with a high side of about 220 psi. Your coolant temps look normal. Have someone turn off the engine while you observe the Main Fan - the gurgling you are hearing is probably the a/c system equalizing pressures at shutdown.

 

Hey SunCr, didn't you mean 238* on the Aux.

 

The fan configuration has changed through the years. You folks are mixing apples and oranges.

 

I'm not. You are right though the 1994 FSM does not apply.

 

Never seen a 238 spec for the L98 Aux Fan - but it really doesn't matter because the option is mere window dressing. Plenty of Vettes left the Factory with a single cooling fan with the same specs; ie, grounding the Main Relay at 226 degrees or when the high pressure switch opened at around 220 psi with the a/c on. Those cars didn't form long lines at Dealerships because they were overheating. The option was worthless - maybe that's why some dealers ordered the Heavy Duty (bigger) radiator without it - though if it's coming on a regular basis, that's a good indication that something else is wrong so maybe it does have a purpose.

 

He never stated what year. His icon says a 1987 and a 1996. That is why I clarified my statement with the year. My fruit is all of one type.

 

on my 90 i oredered a 215 on 190 off switch for a f-body stuck it in my head a used it to ground both fan relay works great running both fans

 

On the 87, the main fan comes on at 228 F and the aux fan comes on at 238 F. If you turn the a/c on, the main fan comes on. When you shut the engine off, what you heard was the main fan coasting. Ign off, the fans cannot receive power because their relays get power through the ign sw.

 

to make the fans run after the key is turned off until the temp sensor senses motor is cool. Simply find the ignition feeds on the relays and run battery power to them.

 

I appologize for the year model confusion....87 references grad year.....My baby is a 96. The "gurgling" is definately the overflow. I have the correct anti-freeze (even got it from the dealer). I am pretty sure the primary fan is not runing...it is hard see. I used to hear it "squeak" when it was coming to a stop and I don't hear it any more. I got a bit banged up during hurricane IKE (shattered both my heels as a vicously attacked the concrete patio from a ladder) but I will try to see if I chalk it to see if it s spinning. I got to drive her for the first time last weekend since the hurricane She ran fine as long I was moving or the AC was running. I did not let her get up to the 228 range. I figured that I was getting in the danger zone around 220.

 

Will run the battery flat first.Fan only cools water in radiator, temp sensor is in head.
Need elec water pump for that option to work correctly

 

228 isn't horrible or dangerous. The '96 is different - GM changed the fan design in '90 in anticipation of the switch to R134 refrigerants. These refrigerants reach higher pressures (temperatures) at ambients above 90 degrees, so the secondary became ECM driven and both fans (for a/c operation) are activated by signals from a pressure thermistor in the a/c high line. High operating pressures can contribute to higher coolant temps, but the main bugaboo is that they lead to lousy vent temps when it's hot. The single fan remained adequate for coolant control (non a/c operation), though both fans can also be activated by signals from the Coolant Temp Sensor. Anyway, '96 actually has a 2 speed secondary and that second speed is triggered by a pressure sensor signal somewhere north (if I remember this correctly) of 250 psi. I'd guess that GM was receiving field complaints of inadequate a/c and as far as I know, the Vette was the only vehicle to receive this mod. In any event, troubleshooting these systems takes a Scanner (to read the Coolant Temp and A/C sensor signals) while someone fiddles with the controls and you observe the fans (better scanners will let you command the a/c request and fan signals). I wouldn't go there yet. Assuming it's boiling or gurgling and you did something that necessitated coolant, I'd simply try a new radiator cap first. Lose pressure and it's going to boil over. And if your main fan is never coming on, jumper it to the battery to make sure it runs. If it does, try a new Relay.

 

I believe that the '96 has 3 relays. 2 of those relays should be identical, 1 for the primary and 1 for the secondary fan. You can swap the connectors to the 2 identical relays to verify:
-both relays are working
-both fans are working.

(turn on AC, which activates the primary. Switching the connectors will make the secondary fan become the primary).

 

There is no primary or secondary fan on a 96. The fans run together or not at all. There are three relays to allow the fans to run in series for low speed and parallel for high speed.

 

I had to drain the coolant for another unrelated repair. I do have a slow leak in the AC system but if I am reading correctly, low pressure is not a factor with the fans. I will try jumping the fans.

 

It's not that simple with the 96. Exactly what is your problem? Do you have an FSM?

 

Hman1987,

Your understanding of how your fans work sounds like it has been confused by all the differences between the C4 years.

As mentioned above by a few:

1. the 1996 LT1 has two fans.
2. BOTH fans should run together (i.e. at the same time).
3. With AC OFF, BOTH fans should run at 'slow' speed when the digitial coolant gauge hits or exceeds 228 F.
4. With AC OFF, both fans should run at 'high' speed when the digital coolant guage hits or exceeds 236 F.
5. With AC ON, both fans should run at 'slow' speed almost immediately.
6. With AC ON, if EITHER the digital coolant gauge reads above 236 F -OR- the AC pressure exceeds a pre-set pressure (typically hit during hot weather), both fans should run at 'high' speed.

If only one fan is running at any time, either one of the 3 relays has gone bad (on the driver side of the radiator cover) -or- the non-running fan motor has gone bad -or- there is a wiring problem.