Cooling fans not turning on

[90ZR1#1221]

So I noticed my cooling fans weren't turning on. Checked the fuse it was good. Unplugged the fan switch so now they both run full time. Does this mean the relays are bad or is there something else I need to check too?

[Schrade]

Here's a schematic from some NON-fan diagnostics on a '94 (never mind my notes)...

http://forums.corvetteforum.com/attachments/c4-tech-performance/47626592d1216358054-merged-fresh-opti-pull-pics-and-ignition-stutter-code-crackers-needed-cus10041.jpg

http://forums.corvetteforum.com/attachments/c4-tech-performance/47626603d1216405936-merged-fresh-opti-pull-pics-and-ignition-stutter-code-crackers-needed-cus10042.jpg

[Schrade]

Some other notes on this schematic WILL apply to your testing:

On the '90, ECM harness 'C'; socket '6', is the same as A 11, and 2nd fan 'D' 11, is substituted for harness 'A', socket 10, in the diagram.

http://forums.corvetteforum.com/attachments/c4-tech-performance/47626607d1216413097-merged-fresh-opti-pull-pics-and-ignition-stutter-code-crackers-needed-cus10043a.jpg

[gbrtng]

So I noticed my cooling fans weren't turning on. Checked the fuse it was good. Unplugged the fan switch so now they both run full time. Does this mean the relays are bad or is there something else I need to check too?If the fans run, the relays are doing their job. Did this problem just start and under what conditions don't they turn on? Where is the "fan switch" you unplugged?
It sounds like you are describing a low freon condition ...

[90ZR1#1221]

I unplugged the fan switch on the a/c line located by the right wheel well. I just noticed the problem recently. They don't turn at all if I plug the switch back in.

[gbrtng]

That's not a fan switch - it's a normally open switch that closes when the pressure in the hard line is too low for the AC system to run - it's a safety measure, and the fans will not run in that case. Do the AC control head LEDs blink? If so, the AC system is probably low on freon.

[90ZR1#1221]

That would make sense. I did have to remove an a/c line to replace the lower radiator hose which would have relieved all the pressure. It has a bad condenser so I never thought to recharge the system since it'll just bleed out eventually. I'll recharge the system and see if the fans will kick on again.

[gbrtng]

Best to leave the connector attached - with it disconnected, the AC compressor can run when AC is called for and since there is no freon in the system, you will probably trash the compressor. The fans will cycle normally when the coolant gets hot enough.

[90ZR1#1221]

The fans don't cycle at all. At first I thought I had an air pocket in the cooling system and while I was bleeding it was when I realized the fans didn't kick on at all. The temp just keeps climbing and climbing.

[c4koh]

Hi OP -

Did you ever get this resolved? I've just come back from a short but spirited trip, and I got temp gage up to 260 and the electronic gage at 261. Fans would not come on. I turned the ignition on (engine off), and connected terminals A and B on the ALDL connector... and both fans are running... so wondering why it's not coming on. Will research more.

Steve

[90ZR1#1221]

I have not got my issue resolved. I still have switch on the a/c line unplugged so both fans continuously run. I think I'm just going to put new fan relays on it and a new temp sensor and see if that fixes the problem. I also noticed last time I had it out a few weeks ago the secondary's weren't opening up and it was running like a dog.

[c4koh]

Hi OP,

Sorry to hear issue not resolved. I've been looking through this issue (I did not see any reoccurence of this issue in my own car), but the information in this thread:

http://zr1.net/forum/showthread.php?p=207338

It seems that a good "override" to force the fans on is to have the AC on. I normally drive on nice, fine days, with my roof off, and have the AC on only on short spells to keep it cycling. So usually, AC is off.

Anyway - if I track down anything else will let you know!

[90ZR1#1221]

I'll have to try and see what happens with the a/c on, sounds like if the fans will turn on when I activate the a/c system then it would be a bad coolent temp sensor.