Hey
I've been reading up on fan operation and what controls what fan in a stock setup. I have an 87 tpi setup in an s10 with the factory tpi harness mated to the s10 chassis.

I've gone through all the wiring as I didn't do the install and I've finally got to completing my cooling system as I'd like it.
I have a Hayden temp controller running one speed (should be low) on my dual interepid fans and I've now wired the ecm to turn on the second coil in the fans at the factory higher temp to give high speed. Basically using the factory ecm signal to run fans that already are spinning by other means.


I wired the ecm fan control as per schematics and other sites info using a new relay powered by ignition source 12v and grounding through ecm. Pretty simple circuit. My issue is that the fans come on as soon as the key is powered meaning the ecm is giving ground all the time to that circuit. But I get normal
'Fan on' in diagnostic mode... Or do I? I do have to turn the key for diagnostics...

Would a faulty cts cause something like this? I did check it against two others and checked out very similar in readings, and also the car does go from open to closed loop after idling. Relay is brand new, wiring is brand new.

What else could cause this? I haven't seen a fan switch yet and shouldn't that only control secondary fan operation directly no through ecm? Maybe a fan switch wire not grounded on a normally closed Circuit? A/c pressure switch not hooked up but is a normally open circuit...?

I also have a hard start after the truck is warmed up ( say deive to the grocery ayore and let it sot for half hour ) but starts first half crank when cold or sat overnight. Also sounds like a cts symptom. But why would three cts read wrong the same way including a new one?

Sorry for the log story, just baffled and thinking out loud.
Thanks for any help, Art

 

Found it! My a/c pressure switch was not grounded is it is a n/c circuit. Joined it with the Ganged ground for the ecm and fans are off