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Coolant temp switch qestions

SV-BDN

NAXJA Forum User
Location
Colorado
I'm running dual E-fans on mt '93 XJ (4.0l, 5spd, mostly stock) and I have a lower temp thermostat installed. Currently its a 160f, but I will be going to a 180f once the cooling system is all sorted out.

I would like to put my e-fans on a temp switch instead of the current manual switch, and I have found some aftermarket temp switches that are in the temp range I am looking to run (185F+/- On - 170F+/- Off). These are single prong grounding temp switches that would thread into the thermostat housing (3/8th NPT)
similar to this one:
https://www.amazon.com/American-Vol...796497C4/ref=pd_sbs_263_5/144-0764993-3592141

I have noticed however when I unplug that temp switch, the Check Engine Light turns on. I do not want to have the CEL light on all the time! I also do not want to lose my temp gauge functionality.

My questions:
Which of my two temp sensors sends a signal to the temp gauge in the dash?
What functions does the temp sensor in the thermostat housing serve (1993 model)? Can it be replaced?
If the temp sensor in the termostat only runs the fans, can I replace it with an aftermarket one (as above) but leave it connected to the stock harness to avoid the CEL?

Thanks in advance!
 
It's easy. The one that gives you a check engine light is the one for the ECM. The purpose of that one is for fuel management. It detects the engine temp and changes the amount of fuel it gets. For instance, you would need more for initial cold start than a subsequent warm or hot engine start.

If you want to install a separate temperature switch, use one of the unused block drain plugs. Another option is to use a radiator probe switch.

Any reason you're using an electric fan?
 
Thank you, I figured there was more to that temp switch when it threw the CEL.

I'm running dual electric fans because I rearranged my accessory layout with an AC delete (wasn't working) and moved the alternator up with a RHD bracket which eliminated the mechanical fan.

I also appreciate the slight power gain from the engine not having to turn the mechanical fan or the non-functional compressor. Its not much, but every little helps.
 
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