I have 2 fans on my 91 Z. Are both fans supposed to come on when the A/C is turned on?

The passenger side fan is not turning on, and I think it may be the fan switch. I tested the relay, it seems OK, and I grounded the wire coming out of the fan switch, and the fans turn on, so it appears to be a bad fan switch. However, that shouldn't affect A/C operation, as the primary fan turns on when the A/C is engaged.

I just bought a JET stage 2 chip (I have a 180 thermo in), thinking it would turn the primary fan on at a lower temp, but unfortunately it does not affect the ECM controlled fan. :\ Is that supposed to happen? I thought chips like hypertech and JET were supposed to turn the fans on sooner. I'll probably pop in a JET fan switch in during the weekend, but I would prefer the primary fan to come on first instead of wearing out the other fan...as a backup system.

Has anyone changed a fan switch without flushing coolant? I'm feeling kind of lazy. How much will shoot out?

Thanks.

 

your other fan won't come on til about 237*... chip won't do anything about it - you need to change the switch - in the pass side head, between #6 and #8 plugs... depends on how fast your are as to how wet you'll get and how much fluid you'll lose... what i'm telling you is if you just pull the switch and let it go, you'll lose a good amount... if you do it two-handed and plug the hole with a finger while you swap switches, you won't lose that much. obviously up to you...

KAM

 

Hehe, thanks.

The thing is my ECM controlled fan isn't turning on sooner with the JET stage 2 chip.

I take it that the secondary fan (non-ECM) isn't turned on with A/C?

 

According to the wiring diagram the fan that's supposed to come on with the A/C on is the passenger side fan.

 

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Thanks MDFormula350, but the diagram doesn't seem to be what's happening on my Z28. A/C turns on the primary fan (the drivers fan) and the drivers fan turns on at 222 or whatever it is. I had the fan switch wire disconnected when I tested which fans come on so I know the drivers side is ECM controlled. My passenger's side fan never turns on, and I'm fairly certain it's the fan switch (or the wire to the switch is open).

Is it possible it is different for firebirds?

 

Driver side IS driven by ECM, on at approx 220. Pass side driven by fan sw on at approx 238. Ground the pass side fan sw wire, it should turn on pass side as well as driver side fans. The ECM defaults if the pass side is turned on before the temp hits 220 so don't let that fool you. If the pass side fan doesn't run, swap the fan relays. The pass side fan sw runs the relay, not the fan directly like some cars. Your primary fan will also run if you run trouble codes from the ECM, that's a good way to test it also.

 

Thanks Danno.

I was actually asking if the A/C is supposed to turn on the primary and secondary fans. It only turns on the primary. I know my fan switch is bad and needs to be replaced, I've already tested the relay on the secondary fan and it is fine.

 

Primary should come on with AC request from control panel. Secondary is controlled by AC pressure and will cycle on and off as needed, but normally will not run continously until the temp threshold(238) is reached.