Hi guys,

my 90 T/A 305 has the dual fan system.
Operating temperature is fine, somewhere around 175, at least both the gauge and ECM concur on that, yet most of the time my passenger side fan comes on.

Which one of my fans is primary and which is secondary? That's what I can't find anywhere.

My A/C is empty so there's no pressure my secondary fan switch could detect from there and I highly doubt there's high enough pressure in the cylinder head.

 

I believe the secondary is the passenger side fan. If you or the PO installed a lower temp switch in the passenger side head, then that could cause it to come on earlier than the primary. I remember when I first bought mine, I replaced that switch (something ~240*F) with a much lower temp switch until I bought the equipment to program my own PROMs and control it with the ECM. The new switch was around 180*F and came on way earlier, essentially reversing the roles of the fans. The primary fan comes on at ~220*F, which is obviously higher than the 175*F you're running at. Here's the article btw, just in case: https://www.thirdgen.org/electric_co..._spec_mod_dual

 

Thanks for the info!
It's not always that the fan comes on when reaching operating temperature, so I'd rather guess the switch has corroded and closes earlier than it should.
As long as it doesn't fail, I'm fine with it, but I'll keep in mind to replace that thing.

 

Heres a very simple way to fix your problem and have it adjustable to whatever temp. you want. I just had a guy here install it and he could not be happer.You only use the controller and follow this diagram and your done for $ 17.99
Adjustable switch = http://www.autozone.com/autozone/par...67187_69565_0_

 

Great idea. I'll keep that in mind. Seems easier than replacing the damn switch.
AutoZone seems to be offline right now.