Second sensor on thermostat housing?

imactj2004

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what is this?

4D99FB82-24BB-4A4C-8489-9BAA07E62396.jpeg
 
interesting. I’m getting p1281 “check ECT” error but Ive replaced the sensor (which was clean), installed a new thermostat (also clean but see note) and I’m still getting the error.

Wonder if that fan sensor/connector lead might be causing the problem. The lead literally snaps on to that sensor port. And not sure if its visible but the black insulation is broken. I’d like to fix or replace but the problem is…i dont know what it is. previous owner installed. Ugh.


side note: When I pulled the old thermostat, it was a 165 degree model. I know that’s a no-no, but Im wondering if it could/should work in tandem with the aftermarket aluminum radiator and electric fan setup.
 
interesting. I’m getting p1281 “check ECT” error but Ive replaced the sensor (which was clean), installed a new thermostat (also clean but see note) and I’m still getting the error.

Wonder if that fan sensor/connector lead might be causing the problem. The lead literally snaps on to that sensor port. And not sure if its visible but the black insulation is broken. I’d like to fix or replace but the problem is…i dont know what it is. previous owner installed. Ugh.


side note: When I pulled the old thermostat, it was a 165 degree model. I know that’s a no-no, but Im wondering if it could/should work in tandem with the aftermarket aluminum radiator and electric fan setup.

Ok so there is an electric fan setup but either way the T-stat should be 195 deg and the Stant super stat's are very popular. As for the fan, is the system cycling properly and what temps are you running at by the dash gauge. Look around and see if you can locate the fan controller.
 
Ok so there is an electric fan setup but either way the T-stat should be 195 deg and the Stant super stat's are very popular. As for the fan is the system cycling properly and what temps are you running at by the dash gauge. Look around and see if you can locate the fan controller.

temp is consistentl190-200 based on the gauge, although I havent confirmed that through other means.

The system does seem to be cycling properly, yes.
 
temp is consistentl190-200 based on the gauge, although I havent confirmed that through other means.

The system does seem to be cycling properly, yes.

Good news, so at least you know what it is and it appears to be functional. An inexpensive code reader will give you actual temp readings. Either way change out your stat and locate the controller and see if there is any info to track down a replacement sensor, but I suspect any generic sensor at the correct temp would do.
 
Okay, maybe I’m missing something. How does that relate to this? I need to track down what this sensor is so that I can replace it.

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Cool, yeah. Been looking at these. Still trying to find one that received the same lead-wire connecion. Will keep lookin.

Thx all.
 
Cool, yeah. Been looking at these. Still trying to find one that received the same lead-wire connecion. Will keep lookin.

Thx all.

Was trying to get you to look around under the hood for the fan controller, should be at the other end of the sensor wire. Could be product info there to help source the sensor.
 
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Cool, yeah. Been looking at these. Still trying to find one that received the same lead-wire connecion. Will keep lookin.

Thx all.

What that sensor looks like is the terminal was unbolted from the sensor and reversed to point toward the housing. I would look for a sensor with a stud terminal and swap the connector on the wire to a ring terminal. I usually use a 221 degree sensor if I use an electric fan.
 
What that sensor looks like is the terminal was unbolted from the sensor and reversed to point toward the housing. I would look for a sensor with a stud terminal and swap the connector on the wire to a ring terminal. I usually use a 221 degree sensor if I use an electric fan.

this is what it looks like when not broken. the prev owner had a 165 thermostat and this fan sensor which was probably a 195 on/175off sensor…both of which are keeping me at a lower running temp and causing the damn P1281 fault code. grrrr

AD6026BA-0584-4E56-B893-36DCC9E89C78.png
 
Hate me or not for recommending this but everything that previous owner did to your TJ's cooling system to convert to an electric fan was a well-intentioned but ultimately a major downgrade in both cooling ability and reliability. Really. If that was my Jeep I'd convert it back to the factory cooling system including going back to the serpentine driven engine fan.
 
Hate me or not for recommending this but everything that previous owner did to your TJ's cooling system to convert to an electric fan was a well-intentioned but ultimately a major downgrade in both cooling ability and reliability. Really. If that was my Jeep I'd convert it back to the factory cooling system including going back to the serpentine driven engine fan.
haha, yes, I've been reading your posts on this topic on other related threads. Not sure what his intentions were (it was my father-n-law, now deceased). He did take it into Nevada/Arizona hot spots but I have no idea how successful he was with this setup. I'm in temperate northern california coast weather so I'm not too worried about overheating but i do need to pass smog now so I need to get the fan sensor in there. Best advice for on/off temps with this afermarket setup? 210/195? or 200/180? or...?
 
haha, yes, I've been reading your posts on this topic on other related threads. Not sure what his intentions were (it was my father-n-law, now deceased). He did take it into Nevada/Arizona hot spots but I have no idea how successful he was with this setup. I'm in temperate northern california coast weather so I'm not too worried about overheating but i do need to pass smog now so I need to get the fan sensor in there. Best advice for on/off temps with this afermarket setup? 210/195? or 200/180? or...?
You definitely (!) must be running a non-failsafe 195 degree thermostat. If the engine isn't fully warmed up which means at or very close to 210 degrees odds are not good it'd be able pass a smog test. Even letting it cool off too much before the smog test starts can cause it to fail.

Non-failsafe thermostat because the "fail-safe" versions are anything but failsafe, they are well known to hang up in the open/non-functional position.

And those who wheel where it gets really hot in SoCal's and Arizona deserts have settled on staying strictly stock where the cooling system is concerned. The only TJs I ran across that were overheated while wheeling there were running aftermarket cooling systems, especially those with electric fan conversions. My stock cooling system never overheated in those conditions.
 
You definitely (!) must be running a non-failsafe 195 degree thermostat. If the engine isn't fully warmed up which means at or very close to 210 degrees odds are not good it'd be able pass a smog test. Even letting it cool off too much before the smog test starts can cause it to fail.

Non-failsafe thermostat because the "fail-safe" versions are anything but failsafe, they are well known to hang up in the open/non-functional position.

And those who wheel where it gets really hot in SoCal's and Arizona deserts have settled on staying strictly stock where the cooling system is concerned. The only TJs I ran across that were overheated while wheeling there were running aftermarket cooling systems, especially those with electric fan conversions. My stock cooling system never overheated in those conditions.

totally get that...just want to know what on/off temp to get with current setup
 
totally get that...just want to know what on/off temp to get with current setup
I Googled it and the answers were so widely varying without consensus that there was no definitive answer for an engine with a 195 degree thermostat. You don't want it running 100% of the time so I wouldn't guess 210 degrees or lower. The above 221 degree suggestion seems reasonable to me, this electric fan business on a TJ is not a strong point for me.