If I have my radiator fan operating off of a toggle switch do I need the fan switch temp sensor between cyclinders 6 & 8? Does the ECM use this for reference? The plug needs to be replaced and if I don't need it I'm not gonna replace it.

 

The LEAST RELIABLE PART of any semi-automatic or manual system, is THE HUMAN upon whose unerring action it depends.

Using the human as a backup to failure of the automatic system (think autopilot) is a WHOLE OTHER MATTER.

All it takes to BURN YOUR CAR TO THE GROUND, is to forget ONCE to flip that switch.

Benefits of eliminating the automatic switch:

• [crickets - there are NONE]

Benefits of retaining the automatic switch:

• Stability
• Dependability
• Repeatability
• Independence of the unreliable human

Retain the automatic one.

 

Over the years Sofa, over 20 years now I’ve been on these hallowed forums and you’ve been a consistent stream of useful information regarding everything automotive and philosophical, always there with sage advise for the newbies and lifers alike to our beloved f-body platform and though I agree with everything you just said, it doesn’t answer my question?

 

That sensor in the head is for the high - high temp fan turn on. ECM uses another sensor.

 

If the plug needs replacement, then do it.

The ECM doesn't need it but the fan does. It directly controls the fan relay. It's not a "sensor"; it's just a switch.

 

I'm with Sofa....replace the switch...it only grounds out the fan so the ECm doesn't need it to work properly. OR...best of both worlds.......install a manual override switch in case the fan switch fails again. So you got the factory switch and a manual toggle you can turn on whenever.


BUT.....It;s a lot more work to install a manual toggle switch than it is to install a screw in / screw out fan sensor. you'd need to find the right areas to splice into, get a switch, run wire into the car, mount the switch etc...

just go from the bottom..its easy to reach.

 

Like I said I agree with Sofa as well, I was just looking for a simple answer to my question so I can decide which route to take to correct what I have. Years ago when I swapped out the 305 TBI for a 350 TPI, i wired in a toggle switch for the single cooling fan. The engine harness was converted from a MAF harness to a SD harness. Fast forward a whole bunch of years with my daughter taking up all my time with karate/soccer/softball and the car sitting in my garage in perpetual disassembly, I’ve been doing a ton of work to the old girl to get her to the point where I can get her on a auto cross track. Some of that work is fixing stuff I did years ago that isn’t correct.
Since the ECM doesn’t use a reference from the fan switch I’m going to go with a stand alone fan switch/relay system to automatically control the cooling fan operation, I’m do this to prevent any more bastardation of my wiring harness as I don’t have the components to put it back to stock, I’m not even sure what wiring is still there, Putting it back to stock is going cost more and take a long time.

1989karr/Sofa
”best of both worlds.......install a manual override switch in case the fan switch fails again. So you got the factory switch and a manual toggle you can turn on whenever.”
Are there any good wire diagrams out there to reference?

 

The switch provides a ground when it reaches the target temperature. To verify this, remove the wire going to the switch and ground it. If it's hooked up to a relay like it should be, the fan will turn on.
To add a switch, simply splice a wire into the existing wire, and run that back to a switch, which connects to ground on the other side. That's all there is to it.

 

There is no fan relay on the car 🤷🏼‍♂️

 

Thats odd...there should be a fan relay...but if you are installing a stand alone system that won't matter.


This works well. theres a good diagram in there.



Running a second cooling fan switch - Third Generation F-Body Message Boards


there you go.


To install an emergency toggle switch just install the switch to ground in-between the relay and thr PT7701 connector.

The circuit will normally use the temp switch to ground, but if you ground it with the switch, it will manually turn on.

 

I used the above linked wiring set up for my emergency fan...I also hooked up a emergency manual switch.... but used a rad hose adapter that would fit a GM fan switch. it kicks on and off nicely.

 

you can also hook up a dual fan set up but yo'll need to do a bit more wiring and use a second relay as well .

 

 

Basically that. I used an add a fuse from the radio since it switches on with the ignition.

why not got LS1 fan? The install is pretty easy. once you get the wiring down.

 

what size fuse are you using with the add a fuse? Is there another ignition switched source in the engine compartment, preferably on the driver side?

the single factory fan works 🤷🏼‍♂️ Now when I need to replace the fan then I’ll probably look into an upgrade like the LS1 fans.

 

I used a low 5 or 7.5 amp.fuse it's just activating the relay so it doesn't need much draw. Theres a certain way the add a fuse needs to be facing though...there's a video on YouTube explaining which side should be on the power side.

off the top of my head I don;t know of anything on the driver side, or in the engine compartment that can be tapped into.I just poked a small hole in the plug for the clutch hole cover (i got an automatic) and ran the trigger wire to the under dash fuse box...its be easier if these cars had an actual fuse box under the hood like most cars did lol

oh, this was for a 305-87 TPI car with a single fan btw

 

Might tap the power wire back to the fuel pump? Be coming off the Fuel pump relay and would be hot when the engine is running.

 

Update: Following the above information the fan is now (hopefully,motor no worky yet) primarily controlled via the fan switch once again with secondary operation through the rocker switch

 

Yay!