Hi Guys,

I readt an aftermarket chip can turn on the cooling fan earlier than stock. A mechanic friend of mine say the computer has nothing to do with it and the chip cant control it.

Who's right?

86 Iroc

Thanks, Dora

 

If your fan is controlled by the ECM, then yes, you can tune the computer (reflash the memcal) to change the turn-on and turn-off temperatures.

If the fan is controlled by a temp switch in the head (and possibly also A/C), the computer has nothing to do with it and you would have to replace the switch with one of desired temp setting.

Not sure which system your '86 IROC has, I'm sure somebody will chime in shortly with detailed info.

 

'86 Iroc fan is turned on and off by prom. On the dual fans in later years, one is controlled by prom (ECM), and the other is a temp switch in the head, with AC mixed in there somewhere. But regardless, the fan on/off temps are controlled by the ECM via the PROM on an '86 IROC.
I could not control the temp in my '86 after installing a 350, so I added dual pusher fans to help. Once I reprogrammed the prom to turn the fan on at 195 and off at 190, I have yet to have any cooling problems. It seems as if once it got heated up to the temp that the factory turn-on temp was, the single fan had a hard time getting it back down, but it can handle keeping it down by turning it on at cooler temps (if that makes sense).

 

The electrical shop that will do the work swears that it's not control by ecm. I remember it going on around 190 or so with the moded chip.

Right now we are using a flip on switch. Anybody else?

 

I'd stick with Iceman.
Ask the shop to show you the wiring diagrams for cooling fans for your car and point to where the relay is activated. Maybe they have an obsolete repair manual?

Or maybe they are trying to convince you so that they can work on your car and get some money. I see that happen all the time.

 

It's easy for them to get confused, because some cars are by the ecm, and some are not.

Quick reference (I think):
Compu-Carbs (lg4,l69): Not ecm controlled (standard temp switch).
TBI: Not ecm controlled (standard temp switch).
TPI: Primary fan ecm controlled, secondary fan not ecm controlled (standard temp switch, or AC pressure).

v6: Single fan, ecm controlled, with redundant standard temp switch as backup.

 

Thank you all very much!