Cooling Fan Question

[adfac]

I have an 86 with a new L98 engine. The fan works fine, coming on at about 175 which alot of you may think is low but it works for me. Normal operating temp is 200 - 220. But when you turn the A/C on, I'm told the fan is supposed to come on automatically, regardless of temp, which it does not do. I'm told that this could damage the A/C eventually so I wait to turn the air on until the temp as reached about 175 and the fan has come on. I have a new compressor and accumulator and the air works fine. I can't find anything addressing this problem in the FSM so I thought I'd ask if anyone might have any ideas as to why the cooling fan won't come on when the air is turned on but otherwise operates normally. Thanks for any ideas.

 

[lefoy84]

Sounds like someone has done some creative wiring. Is the ECM triggering the fan or some aftermarket switch? Put it back to stock.

 

[adfac]

Sounds like someone has done some creative wiring. Is the ECM triggering the fan or some aftermarket switch? Put it back to stock.

The ECM controls the fan. I put in a new ECM when I replaced the englne.

 

[Hib Halverson]

I think there is misunderstanding of how the cooling fan works on an 86. The statement that the fan runs all the time when the A/C is on is incorrect.

There are two situations where the main cooling fan is enabled:
1) ECT over 234 deg F
2) A/C head pressure over 233 psi.

Note that if the A/C is on but the head pressure is below 233 psi, then the fan will not run. If you're unsure whether the fan is coming on at 233 psi, you need to use the cooling fan diagnostic tests in the FSM and you may need a set of A/C gauges to read the head pressure. If you find, using the FSM diagnosis and reading head pressure that the cooling fan is not coming on when it should, then the FSM contains troubleshooting info. for that situation, too.

Obviously, if your fan comes on at 175, the ECM calibration has been changed. That aftermarket cal may or may not impact cooling fan operation in response to the A/C's head pressure switch.

 

[adfac]

I think there is misunderstanding of how the cooling fan works on an 86. The statement that the fan runs all the time when the A/C is on is incorrect.

There are two situations where the main cooling fan is enabled:
1) ECT over 234 deg F
2) A/C head pressure over 233 psi.

I wasn't aware of that. Thanks for the info.