TIMSPEED

Last night, I was driving home in my 87, and I noticed that the coolant temp. was getting kinda high while I was in the drive-thru at MickeyD's. I heard the fan running though, so I was like "WTF?" Then when I got home, I noticed the main fan wasn't moving, but the auxillary was spinnin fast. Now, last week, I put on a new auxillary fan switch from Mid-America, so the auxillary would come on at 200º, and turn off at 185º. So...would it be the main fan motor? Because isn't the relay for the Auxillary on the same relay as the main? Might it be the fusible link for the main. It's all weird, because one works and the other doesn't. :confused: :confused:

davemach

auxillary fan is controled by that switch you installed, the main fan is controled by the computer set to come on at 227* if I recall. If you want the main to come on sooner the way is do that is get a custom chip.

Rich B.

I had this same problem last week; same 200* booster fan switch, too.

I spliced in a new section of wire (w/connector) for the temp gauge sensor (on pass side head) and now it all works OK again.

I have my ECU set at 195*, but the booster fan was still coming on before the main fan. I swapped the OEM fan switch back in. (It leaked a bit anyway).

I don't know if the wire splice (the lead coming up from the starter bundle) did the trick or not; but I did notice that the main fan sensor (under the TB at front of manifold) had what seems to be the same wire...

jfb

The main and auxiliary fans have their own relays. The factory ECM turns on the main fan at 228 F and the switch in the block between #1 & 3 cylinders turns on the aux fan at 238 F. Hope this clears things.

Marcho Polo

Tim,

They all have it right.... the Computer controlls the main fan, and the aux fan is controlled by the temp sensor in the head. They run independent of each other. Since your aux fan is kicking in at 200, it probably doesn't get hot enough to run the main fan since it comes on at 228.


That main fan is controlled in the chip. If it were set to the same as the aux fan (200), they would both come on at the same time.

Vic'89

I agree with Marcho Polo's response above.

If the aux fans comes on before the main fan, the temp will never get hot enough for the main fan to come on.

Remember the Aux fan is really just a backup system for the main fan. You don't want the Aux fan to come on before the main fan.

Since the main fan is controlled by the computer, you need to program the main fan to come on at 180 degs for example.

Vic

Red85

Ground your ALDL connector and see if the main fan runs. If it doesn't, pull the relay and jump the outside pins with a paper clip on the connector. If it runs then, it's the relay (the two center pins are for the IGN and ECM wires).

h rocks

[QUOTE]

If the aux fans comes on before the main fan, the temp will never get hot enough for the main fan to come on.


I have mine switched to kick both fans on at 180*. I did that because I could definitely get mine hot enough to kick the main fan on after the aux fan had been running. This would be in summer at either an autocross where you don't have much air movement due to low speed, and high RPM's, and little opportunity to cool it down after runs, or at the track running 1/2 hour sessions in the heat.