Ultraman asked me for a how to on the manual fan switch.

First, this is for a 92 LT1, so you'll probably have to check the wiring diagram for the correct color (wouldn't surprise me if your 90 and the 92 are the same but, check it.).

NOTE:, on LT1s, the manual fan switch will cause a code 28 to appear in module 4.1. This is because the Quad Driver monitors voltage for the fan relays. manually turning them on will throw the code but no SES lights. Personally, I ignore that code, clear it whenever I check for codes but could care less if it gets thrown.

The relays on a 92 are on the left side of the radiator shroud, one for the primary fan, one for the secondary fan.
Only one fan is needed to cool the car down in traffic.
I used the secondary relay.

Find the relay ground wire in the harness at the relay (it's easier to work on if you either unbolt the relay from the shroud of unclip the connector). The secondary relay is the one closest to the windshield, the ground wire is blue/white (green/white on the primary relay).

Pull that wire out of the harness a bit and remove enough insulation so that you can solder a wire to it. Don't cut that wire, just solder the new one to it. Tape that connection up (suggest using self sealing tape).

Run the wire (16-18 gauge is fine) you soldered on into the cab. Hook that wire to one side of a toggle switch. Any toggle switch will do (RadioShack, Autozone). It can be a 12v to 120v switch, amperage doesn't matter, it is just grounding the relay and doesn't see the amps that go to the fan motor.

Wire the other side of the switch to a ground under the dash, there's screw behind the left carpet panel.

You can also install a LED that tells the dumbass driver (like me) that the fan is on so you don't forget to turn it off. A 12v LED at Radio Shack is $2. Run a wire from a "key on" hot wire thru an inline fuse to the LED and from the LED to the same side of the toggle switch that the relay ground wire is attached.

On an LT1, I don't even bother with the switch until I see 220 and know that I'll be in traffic for a while.

Pics:
Relays
My hidden toggle switch
The location of the fan LED (the green one on the left side of the dash.

Attach file:

---

  2006-02-19 05-18-08_0001.JPG (0.00 KB)


  2006-02-19 05-19-07_0002.JPG (0.00 KB)


  2006-02-19 05-19-54_0004.JPG (0.00 KB)

Hey thanks Bill, that doesn't look to tough, I will put it on my winter list.

Hey thanks Bill, that doesn't look to tough, I will put it on my winter list.

Quote:

Yea, it's easy. the only PIA is running the wire into the cab.

Be sure to double check the wiring color for your 90.

Here's how to manually override both fans on an 85. When the switch is off, it reverts to factory control.


http://webpages.charter.net/khasting/techinfo/fanoverride.html