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Author Topic: Water Temperature Gauge Reading full hot/Dead center Issue (Not Coil Wires)  (Read 93 times)

Offline 2468wdwa1

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I know there's a thread either here or on one of the toyota truck forums about soldering the coil wires back on, however that is not the issue that my water temp gauge has and I haven't seen anything on my issue in any of my research (and I've done ALOT, as NOS temp gauges seem to not exist anymore, despite showing as in stock in a few places). The issue with my gauge appears to be that the diode that is to the upper left of the gauge when viewed from behind is bad, and the testing I did was the factory manual testing: Where U is the left post, E is the bottom/middle, and IG is the right post, IG-U resistance should be ~56 ohms, U-E ~201.8 ohms, and IG-E ~145.8 ohms. Only IG to E had any reading, though it was correct. I then followed the circuit board print from U to the diode and tested it, and it had infinite resistance, aka no connection between the 2 sides. I have ordered a NOS 3.0B1 sharp brand replacement diode, and I will update this post when I install it, but I am fairly certain that it is the only issue as all the coil wires were still solidly connected, and the resistor reads correctly. And for reference I have a 1985 Celica GT Liftback w/ the manual, and it has the 130 mph cluster.

Offline 2468wdwa1

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UPDATE: The fix worked! Make sure to have the diode cathode/anode aligned according to the diode symbol on the circuit board (black stripe on the actual diode goes in the same direction as the line side of the diode symbol).

Offline sirdan

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Congrats! I bet the diode was dirt cheap too.
1988 4runner

Offline 2468wdwa1

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It was a dollar plus shipping, ~$5 overall, which for a single diode sucks, but opposed to $40-$50 for a new gauge (that isn't even in stock anywhere I checked) is real cheap, so overall I'd say so! And a $5 fix in general is really cheap for cars

Offline danf

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It was a dollar plus shipping, ~$5 overall, which for a single diode sucks, but opposed to $40-$50 for a new gauge (that isn't even in stock anywhere I checked) is real cheap, so overall I'd say so! And a $5 fix in general is really cheap for cars

That sounds like when I fixed the door lock control module like over 10 years ago. It had gotten wet and popped some resistors and a diode. It did work until last year but alas the thing is dead and I had to wire around it. No more smart locks lol.

I think that repair cost me $2.50 but I have an electronic supply store about 15 miles away from me.
SELECT celica FROM toyota WHERE year<=1985;

1985 GT-S
-Rebuilt engine: bored .020 over, oversize valves, new cam
-Thorley header w/heated O2 sensor at collector & all new exhaust
-Impact6 strut bar
-3.9LSD rearend, which is now slipping
-Lots of bodywork and new paint!
-New cd player to cover up all those squeaks and rattles
-JK short-throw shifter


 

cognitive