Temp sender wiring (1 Viewer)

[Flying40guy]

I've been trying to get the temp gauge working on my '77 FJ40 and I've hit a road block. When I purchased from PO it had an aftermarket instrument cluster in it. I pulled it out and got the oil gauge working but can't seem to get a readout on the temp gauge. I found what I think is the wire that goes to the sender by grounding it. When grounding this wire the temp gauge pegs full right. But when I connect the wire to the sending unit and run the engine it stays full left. I needed to connect more wire to the original wire as the original was cut too short to reach the sender. If the wire that I added was a slightly thicker gauge wire to the original would that maybe be the cause of the problem? I replaced the sending unit a couple years ago from CCOT so I wasn't thinking that would be the problem. The fact the that gauge moves full right when the wire is grounded is telling me that the gauge works. I just don't know why it won't deflect at all when the engine starts to warm up. Thanks for any advice.

 

[pb4ugo]

Is the water temp gauge aftermarket? If so you need to run a temp sender that is compatible or of the same brand.

 

[Flying40guy]

No. Trying to get a readout on the original temp gauge.

 

[1MAC]

If you installed the temp sender with sealant or Teflon tape, it may not be making electrical connection with the block.

 

[pb4ugo]

Your gauge moving when grounded usually means it's the sender or poor ground. Do you have a test light and multi meter?

 

[Flying40guy]

It’s a new cylinder head that had the temp sender fitting already installed. I bought the cylinder head from Poser so it’s legit. I screwed the sender into the fitting and did not use any sealant or Teflon tape. I do have a multimeter but not a test light. Maybe I’ll see if I could get a test light from Oreilly’s.

 

[pb4ugo]

I'd test ohms 1st. Since you have a meter.

 

[Flying40guy]

I tried testing ohms with red lead to sender tab and black lead to ground. Not getting a good ohms reading so I may also replace my old multimeter.

 

[65swb45]

I tried testing ohms with red lead to sender tab and black lead to ground. Not getting a good ohms reading so I may also replace my old multimeter.

Wouldn’t it make more sense to test a few other things with it before deciding it’s the multi meter that’s bad? Especially since more than one person has suggested that the bung may not be grounding properly.

 

[Catching Neutral]

What have you done to your Land Cruiser this week?

Where did you get the mounting stuff for the switches? Waytech? That's how the sPOD comes....it's made for it.

forum.ih8mud.com

 

[JDNs78FJ40]

It’s a new cylinder head that had the temp sender fitting already installed. I bought the cylinder head from Poser so it’s legit. I screwed the sender into the fitting and did not use any sealant or Teflon tape. I do have a multimeter but not a test light. Maybe I’ll see if I could get a test light from Oreilly’s.

Your gauge moving when grounded usually means it's the sender or poor ground. Do you have a test light and multi meter?View attachment 3314752

Not to hyjack this thread but I have the same problem and electrical is just not my thing so be nice. I'll go get a test light tomorrow am and perform test 1. I have a multimeter and did test 4 and got a reading of 50 with the coolant temp at 80 degrees. I know the coolant temp is 80 from my sniper handheld. When I installed the OEM temp sensor back in the block after plating I did use some thread sealant on the adapter that goes in to the block and I'm 99% sure coolerman told me not to use sealant on the actual temp sensor bung. Could the sealant on the adapter be a possible issue with grounding and be causing my problem? Would test 1 confirm that or would test 4 confirm the sensor is grounded properly since I got a reading that matches the manual?

 

[pb4ugo]

I suspect your reading is correct at 50. You can ground one probe to the blk and the other to the adapter. If you have no resistance then the adapter is grounded. You can preform the same test to the body of the sensor.

 

[Flying40guy]

Ok, so I pulled the temp sender bung and as I suspected there was no thread tape between it and the cylinder head. There is also no thread tape between the sender and the bung. So it should be grounded properly. My knowledge of how to use the multimeter is limited. It does have an auto function and when I tried measuring resistance between the sender terminal and ground (with a warm engine) it started at 1.650 and then somewhat rapidly kept climbing. I also tried setting different ranges on the multimeter and no reading came close to an ohms reading from the table in the manual. If any of this makes sense to anyone I’d appreciate some insight. Thanks and cheers

 

[45Dougal]

Sounds like a bad sender.
Set the meter to 100 ohms (this is full scale on your meter at this range, i.e it reads between zero and 100 ohms).
You might only have 1K ohms (1000 ohms; that's also OK but the reading might not be so accurate).
Touch the two leads together, and the meter should read zero or very close to it.

Disconnect the cable from the sender.
Touch one meter lead to the terminal, and the other to the brass outer.
If it doesn't read within the expected range then it's either dead or more likely just the wrong one for your instrument cluster.