Coolant Fan Switch V6 (Page 1/1)
jon m JAN 30, 10:46 AM
Hi does anyone have the part number for the original coolant fan switch that sits next to the thermostat housing ?

I changed mine out for Rodneys lower Switch on which works great in the summer however in the UK as the Temperature is lower than the US - I have found that the Car is running rich as the needle on the gauge only goes to the quater mark then the fan kicks in as it should - I have lost my original to swap it back since moving house which is a pain
Any help much appreciated
Jon
Patrick JAN 30, 11:42 AM

Jon, with a (properly functioning) 195°F thermostat, the fan could run continuously (not that you'd want that) and it wouldn't cause the engine to run rich.
Vintage-Nut JAN 30, 03:42 PM

quote
jon m:
Hi does anyone have the part number for the original coolant fan switch that sits next to the thermostat housing ?



GM 3040674

------------------
Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

fierofool JAN 31, 11:33 AM
If you're using a 180 degree thermostat, the engine can't warm up enough to go into closed loop, so it will likely run rich. Rodney also offers a 195 on, 185 off switch that can keep the engine too cool. I've found with two of mine that the 195 degree thermostat along with Rodney's 210 on, 200 off switch to be ideal, even in Atlanta, Georgia's summer rush hour traffic. The temp gauge sits at just below 200 most of the time. Prior to installing his switch, both would quickly overheat.
Patrick JAN 31, 03:21 PM

quote
Originally posted by fierofool:

I've found with two of mine that the 195 degree thermostat along with Rodney's 210 on, 200 off switch to be ideal, even in Atlanta...



I've found that combination to be ideal here as well (much further north) all year round.
jon m FEB 01, 11:20 AM
Many thanks for your replies

So far I managed to get the coolant switch and replace it - bit of a pain with the vacuum lines etc in way.

My question is is the Thread tapered so it gets tighter as you screw it down ??
Vintage-Nut FEB 01, 11:33 AM
YES - GM 3040674 has 3/8" x 18 Pipe Threads which are tapered

Edit - I use a high-temp RTV to seal the threads; don't overtighten it, and allow the RTV cure before starting the engine...

[This message has been edited by Vintage-Nut (edited 02-01-2025).]

fierofool FEB 01, 04:47 PM
The new switch usually comes with a thread locking paint on the threads. Because the switch grounds through its threads, be careful about using things like teflon tape or other compounds that might insulate the switch and interfere with the ground.