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Discussion Starter · #1 ·
I need help confirming that my temp gauge is shot and nothing else.

Background info... I had big temp swings and a seized fan clutch for a while. Finally had some money and time so installed new clutch, t-stat, and temp sender. Now the gauge sits right at the hot end of the white. At cold (before starting in the morning) the ohms is above 400 and when at temp with the needle to the right side it's at 92 +/- ohms. I also get 10 volts at the wire connector. I've bled the sytem and don't think there are any air blocks. So it has to be the gauge, right?

Thanks!
 

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Kevin, You are getting precisely the same readings I was getting on my 110. I put a new sender in and it was pegged right after startup. Initially I suspected that the voltage stabilizer was the culprit, but the gas guage was right on (then I remembered I took the stabilizer out) I have this gnawing feeling like a bunch of senders were made with the wrong range, but I never knew if the RR guage had the same resistance as the DEF guage. I have a mechanical guage, which I trust, but to get the guage to center at 190F, I ended up sticking a 180 ohm resistor in series with the sender..

What I would suggest, to put your mind at ease, is to take a thermometer, and actually check the radiator temp. I used a meat thermometer, with a long probe, and assured myself that all was well, and the roast didn't taste funny afterwards either.
 

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Discussion Starter · #3 ·
Thanks once again Terry!
Yeah I already did the thermometer in the radiator. Barely past 150º which seems like the radiator is doing it's job. I'll try the resistor, but why 180 ohms? And is there a way to check the actual engine temp instead of the radiator?
 

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Kevin88RRC said:
I'll try the resistor, but why 180 ohms? And is there a way to check the actual engine temp instead of the radiator?
To show my age, I picked up an old Decade Resistor box, like the kind all the engineering schools had in lab. It's just a bunch of precision resistors in a box that can be selected to give a range in 1 ohm increments from 1 to 100K ohms. I put it in series with the wire to the sender and cranked in resistance until the meter was centered, with the engine at 190F (according to the capillary guage).
The only sure way to know the engine temp is with a mechanical (capillary tube type or bimatallic probe) into the coolant stream at the thermostat housing (in front of the thermostat) A probe in the top of the radiator will be the closest point off the engine.
When I was building the engine in the Defender, I drilled and tapped a fitting into the top of the intake manifold, immediately adjacent to the electric temp sender. There is a boss cast into the manifold for this, and comes into the same pocket as the elec sender. I had the guage before this engine, but the thermocouple was in a brass Tee in the heater matrix line, which seemed to give a pretty reliable reading.
 

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Discussion Starter · #6 ·
azpaquin said:
you checked it and the temp was fine..
Yeah, but I'm still confused. What will time do?
Everything checks out. But even though I'm getting a proper reading at the sender and the temp in the radiator is good, why would the gauge be so off?
:confused :confused :confused
 

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time.. pressurizes the system a couple of times

then works out the bubbles.

my temp was pegged the first couple of startups after my cooling system modification.. now it is fine.
 

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Discussion Starter · #8 ·
Still going....

Still trying to figure this damn thing out. I've been away and have had little time to work on her till now.

Here's whats going on now/still. Get her up to running temp and the gauge sits at 3/4s... on highway, city, and sitting in driveway. No fluctuation.
Now the odd part. Still at temp and still running, go take a reading of the sender. Initially it is 40 ohms which I think is about correct for 3/4s on the gauge, but in a couple of minutes the reading settles out to 85 ohms. Test gauge again with 100 ohms resistor and the needle sits around 1/4 on the scale.
Checked voltage again which was slightly erractic. Remove and clean stabilzer. Now holds solid on 10 volts.

I'm thinking (hoping) it's a ground issue, but where does the gauge ground at????
:dunno: :dunno: :dunno: :dunno: :dunno:
:confused :confused :confused :confused :confused
 
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