I recently changed my intake but in my haste I neglected to notice that the boss for the fan switch was not drilled let alone threaded. Not wanting to disassemble everything I bought a thermostat housing that incorporates the the switch. Unfortunately, the housing had a defect. So instead I spliced a 1/2" Tee into the heater core input hose (hose from the water pump) at the firewall, screwed in a 1/2" - 3/8" adapter, screwed the fan switch into that and grounded the Tee.

Just to test the fan, wiring and that the Tee was well grounded I pulled off the switch connector and ran a jumper from the Tee to the connector pin. The fan came on; no problem. But when the car was run the fan did not come on at the temperature that it used to (didn't come on at all actually).

OK, so the switch itself could be bad (I've ordered one for Monday) but they are pretty sturdy little guys. I'm more expecting someone to tell me that the calibration of the switch is no longer correct because of the way I've mounted it. For sure, with it mounted into an adapter the switch sits "higher" in the collant flow that it should. Nonetheless, the tip will be emersed in Prestone that is every bit as hot as the rest of the system.

If the new switch doesn't solve the problem I'll have to buy another thermostat housing. It would be a pity though, because this setup is actually a bit tidier looking.

Anyone have any thoughts on this? Thanks,
Jon

JSD MOD

 

JD, I am not sure of the differences between `83(you) and `88(me) as far as fan switches go. Double check your connections and especially your ground. Most switches need to be grounded to work, you say you checked that so the only other thing I can suggest is to change the location of the temp switch. If you can`t fit it in the intake manifold look for a location on one of the heads. You are right to think the coolant may be cooler in the switches new location vs the old location. Hot coolant flows from the engine through the upper radiator hose to the radiator and exits the radiator cooled from the lower hose. All of the after-market fan switches I have used require they be placed at the hottest location to work properly which in your case would be the thermostat housing.

 

im not too positive but i thought that the fan turn on switch was in the passenger side head. and the CTS ( coolant temp sensor) was in the intake. actually im almost positive, because i replaced my CTS a few months back, and sure enough it was in the front of the intake.

 

JD, from what little I find in my manual, for `83 it looks like the temp switch/sender are written this way which indicates the switch is multi-purpose, it does both and is located in the thermostat housing. This switch does need to be grounded so watch for that. If you want to avoid buying another thermostat housing, look to see if you can mount the switch closer to the upper radiator hose. Look for a fitting on the intake manifold or on the head in the area of the thermostat. Seems easier to buy another housing and do it right.

 

Previously, on the original spread bore manifold the switch was screwed into a boss next to the thermostat housing. I'll guess I'll get another thermostat housing that includes the switch. It's a shame though, it means giving up my chrome water neck and having the switch and its wire back behind the air filter looks a lot tidier.

If I was to ground the connection so that the fan runs all the time should the engine reach operating temperature? I did this a few days ago after letting the engine temp climb to 3/4. After a brief period the fan brought the temp down to about 1/4 on the gauge and it stayed there until I shut it down. Should the thermostsat not have closed a little allowing the temp to rise again? (perhaps its stuck) Did I not give it sufficient time?

 

Hayden has 2 fan switch kits you may want to check out online. One is # 3652 and the other is #3647. Both have a sensor/switch that fits in between the fins on the radiator so you don`t lose your chrome thermostat housing. The 3652 is not adjustable and the 3647 is.

 

Well, we must have some cosmic connection going on here. My local Auto Value is sending me both kits to have a look at this morning. While I like the idea of the adjustability of the 3647 the other one should just wire from my sensor wire to ground.

I may opt for the 3647 if I can get the correct connectors to tap into the existing wiring without hacking it or using shunt clips. This because when I do the heads I'll be changing the intake again for an RPM and I expect I'll go back to the stock configuration.

At any rate, I'll post back with results.
J

P.S> Thanks alot JimDutro.

 

Jonathan D, you are welcome.

 

why not just wire it to a toogle switch so you can turn it on when needed and off when you don't need the drain.

 

Well I'm the type of guy who does notice his gauges but the one time leave the car to warm up with the fan off...and get distracted...

 

JD, smart thinking there. I use a toggle as back ups for each of my fans. There`s no way I would depend only on them instead of the sensor. It only takes one time to forget to turn them on or not notice the gauge and overheat bad enough to cause serious damage.

 

I ordered both types of after market fan switch (adjustable and non). In the end I opted for the non adjustable. While I liked the idea of adjustable feature the Non-adjustable was a quicker install and allowed me to leave my stock wiring untouched.

The probe sits nicely in the rad with one wire grounded to the body and the other extended through the factory split loom around behind the engine and back up the other side to the to the original fan switch connection point.

If I ever decide to go back to the original switch it's just a matter of unplugging the new switch and plugging in the old.

It works great! The car runs a little cooler while ideling is all.
Jon

 

JD, glad to hear you got it handled, good job.

 

nice and simple.