Temp gauge reads to high

[dagenham]

The factory temp gauge needle reads way over to the L most of the time on my 85 4bbl. I hooked up a mechanical gauge and it barely went to 180 degrees on a humid 80 degree evening. So what could be the issue with the gauge? I replaced the sending unit in the intake with a new Motorcraft part and the gauge reads the same as before. IVR? All other gauges read good though. Is there a way to test gauge or adjust needle to correct it?

[erratic50]

Get another fox gauge and swap out temp gauges??

[Matt J]

The temp gauges in these cars are notoriously inaccurate. Mine read at the "L" too, but my mechanical gauge read right around 195, which is right where the 84 CFI car wanted to be, so I just didn't worry about it. "L" was just normal for my car. These units were used in all years with different setups that ran at different temps, so the gauges read all over the place. If you're confident that the mechanical gauge is accurate, then I'd agree that the high end shouldn't be showing for 180 degrees, so it's annoying, but at least you know the car isn't running too hot. Too cool, if anything I'd say, but I'm not sure which thermostat was called for in the 85 carb. If I recall correctly, I think the sending units for the stock gauge needed good metal contact on the engine. It's been years since i took it out, so I'm not positive about that. If it does, and you taped the threads, that might be causing a faulty signal to the gauge. Someone else will have to chime in on that to verify or correct me there. I ended leaving the stock one disconnected because I liked to see the actual measurement so I kept the mechanical one instead. Good luck figuring it out!

[erratic50]

Im thinking it almost has to be the temp sending units. Anyone know what the resistance should be at a given temp?

[ashley roachclip]

Did you use thread sealant on the new sending unit ?
I use pipe dope , and just a bit of that .
I never use teflon tape , won't read correctly if you do .

[dagenham]

Nothing on the threads except what Ford put on them.

[erratic50]

There has to be a way to calibrate the gauge vs the pickup. Anyone here know what it is or who does it?

My gauge on my car hasn't worked quite right since I had to replace the pickup due to it failing. I live with it, but its annoying. About as annoying as having to disconnect the factory gauges or T in some aftermarket or replacing the stock gauges with aftermarket, etc.

The factory stuff has worked for 40 years in some cases. No reason it won't work for 40 more.

[4-barrel Mike]

Try this: pull the gauge out and tap the low side lightly against the palm of your hand (may need a little more than lightly). I just did this with a FMS tach that was too high.

Mike

[dagenham]

What does that do?? Better yet how did you determine a tach was reading to high?

[dagenham]

So yesterday's temps were at least 90 degrees plus with lots of humidity. Mechanical temp gauge went to 190 and stayed there while driving red light to red light thru the city. So now that I've confirmed that the gauge is reading waay to high, what does anyone suggest? Replace gauge, try to recalibrate the gauge I have, look for some other problem as the cause, or what?

[Matt J]

Yeah, that's where mine read around 195 or so. I'll let others chime in who have actually replaced a gauge or somehow adjusted one. I'm afraid though that the thing might not actually be broken, that's just how they read. They weren't good from the factory in terms of giving a useful reading. After all, we can assume that reading somewhere around "m" is good, but we don't actually know what that is for a temp. And since all the cars that used different thermostats and ran at different temps all used the same stuff, lower end might be normal for cooler setups, higher end is normal for the hotter ones. I think it was intended as a slightly more functional idiot light.

I think there might be some direct fit gauges you can put in there if you prefer something accurate while maintaining a relatively stock look, but I don't know if there are any that look 100% stock. Again, I'll let more informed folks answer that. Good luck in your search!

[darkd0r]

You can splice a resistor into the wire from the sensor to the gauge, or build a short extension with the proper connectors, if you're sure of actual engine temps.

Start with a couple of test leads and a 2 watt 5 ohm resistor, although that's just a guess.

[ashley roachclip]

You have mechanical gauges , why worry about it .
I disconnected mine , built a place for 2 gauges where the stupid warning center was , and put a temp and oil gauge there .

[erratic50]

More gauges is less chance of overlooking a problem.

My car always ran on the O of Normal for years and years. I blame the thermal pickups quality and the terrible thermostat quality we see now.

I just bought all new 192 degree Motorcraft thermostats for our foxes. Going to buy Motorcraft pickups too and if that doesn’t cure it I’ll walk the bone yard for an OE temp sender.....

If it’s still inconsistent across vehicles there’s not much else it can be other than the gauges ..... will be my next area of focus. One way or another these cars around my house are going to behave normally again! (damn it!)

Last thought..... gauges are one thing, warnings another. Adding a temp light is never a bad idea if it’s not sky high on warning temp. Something that says hey — stupid — look at your gauges!

[4-barrel Mike]

What does that do?? Better yet how did you determine a tach was reading to high?

The gauge needles are press fit. The inertia of tapping will slowly move the needle to the left (or right if you tap that way).

Tach: I compared it to a known "good" tach.

Mike

[erratic50]

Nice.....