sthamby

The primary fan on my 1993 corvette does not come on when the engine reaches high temperatures. The only way it will start is to turn on the A/C. The secondary fan does not kick on at all. I grounded terminals A and B on the ALCL under the dash, turned on the ignition, and both fans ran. Could it be the cooling fan switch? Relays? Appreciate any help.

theadmiral94

What is 'high temperatures' and which gauge are you reading (digital dash or analog gauge) and do both gauges agree or nearly agree?

Given your testing the adlc, it implies the fan motors and fan relays along with the ECM's ability to control the relays are all working fine.

it's possible that the ECT (engine coolant Temperature) sensor (mounted in the front of the water pump) is disconnected/damaged, but likely that would also cause engine performance problems too.

Regarding the secondary fan, it is controlled either by temp (above 236 F) or AC freon pressure -- so if your AC needs to be charged (i.e. compressor cycling while at idle through 1500 rpm), then that would prevent the secondary fan from coming on when the AC is turned on.

jfb

The main fan comes on at 228 F and the aux fan comes on at 238 F.
I'm guessing your engine never gets to 228. The a/c normally turns the fan on.

sthamby

I just got the car a week ago and haven't had much time to drive it since. I didn't know the digital gauge was there. I also didn't look close enough at the scale on the analog to realize it isn't linear as far as the middle mark actually being the median of the temperature range. It was running around the 3rd mark or a little over which according to the gauge I guess would mean about 195-200F? The A/C compressor is cycling while idling, every 10-15 seconds or so. I'm guessing a '93 model still uses R12 and not 134A? I'll get it charged and see if the secondary fan comes on then. Thanks again.

vette poor

what is hot on a 93 I'm having the same problem had a fan go out,so I changed that changed the relay which the fan burnt up along with the connector changed the thermostat, had a 160 which looked fine still running up to 210 -220 and starts missing and running rough, and cutting out.

jimg's'93

My primary ('93 LT1) rarely ever comes on unless I specifically let the engine idle and heat up. In that case the primary comes on at ~220F. I have yet to see the secondary fan come on as the primary quickly returns the temp to below ~215F. Normal operating temp on my digital is ~186F.

BTW...FSM states the secondary is set to enable at ~226F.

vette poor

I'm freaking out ,my 78 would be frying at 226 so the 93 is stressing me out the first fan to come on is the right one which I guess would be considered the primary?

BADDUCK

If you are freaking out now you will be suicidal by July.

vette poor

I,ve had my 78 for 2 years been a on going project just waiting for the new 388 stroker to finish it, less than a month to go, just traded a boat for a 92 that had been sitting for several years, then traded a truck for a 93 a month later and trying to get all the bug worked out of both of them.

Ken Isom

93 coolant fans schematic.

93

puterami

11 years ago. Hope he has it fixed by now.
This happened to me when I was new to the forum, too.
There's a way to turn off the additional threads feature.