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Anyone ever swapped out an OEM dash temp gauge?

W

wgregt

NAXJA Forum User
Location
SoCal
Looking for tips/thoughts on doing this. My 88 needs a new gauge, apparently. Says it's running hot, when in fact it is not. Hoping someone has done this before?

Oh...I heard that the later models have a light for hi temp? Is it a gauge as well? Or just a "you're too damn hot" light only? Was thinking that if it's a gauge AND a light, that might be better, but if it's just a 'too hot' light I'll probably pass.
 
Easiest thing you will find to do is just replace the whole gauge cluster. The temp gauge is solidered to a circut board etc it would be very tedioius to replace, if it is in fact the problem and the sensor is good.
 
More than likely its the sending unit in the rear of the head that needs to be replaced. Don't cheap out get a good quality one. I recently replaced my dash gauge because i broke the needle off installing white face gauges its not hard. remove dash bezel remove gauge cluster and three small Phillips hold the water temp gauge. Be careful the gauge is sensitive. :) good luck.
 
well, I've already replaced the temp sender (the brass threaded plug at the rear driver side of the head) and it didn't change a thing: still runs @ 60% on the freeway (above 210 degrees) and sweeps thru the red zone to peg WFO under load/going uphill. Even though it's not running hot (no puking of coolant, no leaks, no steam/hissing) the gauge says it is.

Did you have to remove the speedo cable from the back of the cluster, KryptoniteXJ? Year model you have?

Quality one? It's just a solid brass slug...what's to go wrong in these things?
 
Have you confirmed these temperatures by alternate means?
 
Hmmm...now I'm reading that the dealer temp sender (at the rear of the head) is the one to get? That true? How could they possibly be different? Dealer: $55. Autozone: $8

I wonder if there's a difference, and the gauge is NOT my problem, but the sensor is? I just can't see how these things are anything other than a solid slug that screws in and takes the coolant temp...what am I missing, other than $47?
 
go grab a few different ones from the junk yard thats what I did.
 
It's not solid brass it has a thermosistor inside that changes resistance as it heats and cools. FWIW I've had them be 30 degrees off

Meanwhile the gauge uses a coil that is electrically charged, with the resistance on the sender circuit determining the strength of the coil's magnetic field. If the coil is damaged the magnetic field will be off.

My 91 FSM describes a set of quick tests: With ignition on, disconnect sender and gauge go to low position, then bridge the sender wire to ground and gauge should go to high position. If the gauge does something else the gauge is bad.
 
Last edited:
Tried EHall's tip just now. Worked exactly as he said on my 88: needle went full left to full right upon grounding it out. So, I'm thinking the gauge is good, and my temp sender I got from NAPA, brand new, is somehow different than the OEM one. Maybe the internal resistance is different? Anyhow, the tip saved me a lot of work for nothing, and now I'm off to the boneyard to see if I can get lucky there. Will post results.
 
wgregt said:
Tried EHall's tip just now. Worked exactly as he said on my 88: needle went full left to full right upon grounding it out. So, I'm thinking the gauge is good, and my temp sender I got from NAPA, brand new, is somehow different than the OEM one. Maybe the internal resistance is different? Anyhow, the tip saved me a lot of work for nothing, and now I'm off to the boneyard to see if I can get lucky there. Will post results.
Click to expand...

well it just showed that the coil on the gauge was operational not that it was accurate
 
wgregt said:
Tried EHall's tip just now. Worked exactly as he said on my 88: needle went full left to full right upon grounding it out. So, I'm thinking the gauge is good, and my temp sender I got from NAPA, brand new, is somehow different than the OEM one. Maybe the internal resistance is different? Anyhow, the tip saved me a lot of work for nothing, and now I'm off to the boneyard to see if I can get lucky there. Will post results.
Click to expand...

well it just showed that the coil on the gauge was operational not that it was accurate

I would verify that it is accurate by setting a potentiometer to the desired resistance and chekcing the results, see http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm
 
Well, I went to the boneyard...oh..."recycling facility" and got a temp sender AND a temp gauge out of the dash panel. Installed only the temp sender so far and took it for a little spirited freeway ride and....it seems to have worked. It took a bit to get up to operating temp (which I think is 195...right?) and stayed just to the left of the 210/halfway mark, which I'll call 195. So, I'm wondering...if a cooling system is working perfectly and all components are running @ peak performance, and I have a 195 t-stat in there (which I do) then...it SHOULD run/stay @ 195 then, right? I mean, @ 195 the t-stat opens, which cools it all down/keeps it constant @ 195. If that's right, then I might be spot on...just a bit under the 210 mark. It came up a bit to 210 even under load/uphill now, where before it pegged. I'm gonna give it a few more days of driving to see how it goes, but it looks like the OEM ones are indeed the right ones to get, not the auto store ones.

My fuzzy math on the correct running/operating temp correct?
 
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