Temperature Gauge
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Elder User
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Temperature Gauge
The temperature gauge didn't work for my '85 , so I located the gauge sensor in the manifold of my 302 FI - pulled off the wire and shorted it to ground - gauge went full sweep to pegged hot.
I went and got a new sensor and installed it - now the gauge works; but it only gets up the lowest bar on the cold side of the gauge.
The engine gets pretty hot after driving it around for 15 -20 minutes - water is circulating through the radiator - still little to no movement on the gauge.
Any ideas - I may change the stat tonight - but, I don't think this is the problem.
Oscar
I went and got a new sensor and installed it - now the gauge works; but it only gets up the lowest bar on the cold side of the gauge.
The engine gets pretty hot after driving it around for 15 -20 minutes - water is circulating through the radiator - still little to no movement on the gauge.
Any ideas - I may change the stat tonight - but, I don't think this is the problem.
Oscar
Post Fiend
Joined: Jul 2004
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From: Northern California
Is it afactory sensor, or aftermarket? Sometimes they can be bad.
Are you running a thermostat or not? And if you are, is it the factory temp?
How long did you leave the gauge grounded? If you left it too long the gauge could have been damaged.
How are your other gauges working. Especially the Fuel gauge. Does it read lower than it should as well? If so it can be a instrument cluster voltage regulator problem. They can be adjusted as well, if all gauges are reading low.
Are you running a thermostat or not? And if you are, is it the factory temp?
How long did you leave the gauge grounded? If you left it too long the gauge could have been damaged.
How are your other gauges working. Especially the Fuel gauge. Does it read lower than it should as well? If so it can be a instrument cluster voltage regulator problem. They can be adjusted as well, if all gauges are reading low.
Posting Guru
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From: Niceville, FL.
Go to Radio Shack and buy a 10 Ohm, 10 Watt, 5% Resistor, Cat# 271-131, $1.99+ tax. Use it to substitute for the sending unit. It should make the gauge pointer indicate right on the "Hot" mark if the rest of the system is ok.
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Piffery1 - Thanks - a good test.
81-F150 - I understand - I don't think I fried the gauge - just a few seconds grounded. I think the fuel gauge is reading low; although, oil seems OK, but may read a little high.
81-F150 - I understand - I don't think I fried the gauge - just a few seconds grounded. I think the fuel gauge is reading low; although, oil seems OK, but may read a little high.
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From: Virginia
Also, start the truck cold with the radiator cap off. If you see coolant flow right away in the radiator, then your thermostat is stuck open, or someone has taken it out, and that might be why the gauge is not coming up to temp. On mine, 190 degrees was around the "o" in the word "normal".
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From: Niceville, FL.
I use two complete turns of teflon tape on sensors, never more. The sensor threads cut through the tape and make a good ground connection. Pipe thread sealer or "dope" can cause conductivity problems.
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Post Fiend
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From: Northern California
Leaving the gauge grounded for an extended period, can cause damage to the gauge. It won't fry it, but it can cause it to read innacurate, by pushing the gauge past it's tolerances. IE: way beyond it's hot, or Full, or High mark.
I was always taught to ground it just enough to check movement of the gauge to see that it works, but no more.
As for sealing the sending units, it's better not to use anything to seal them at all, if possible.
I was always taught to ground it just enough to check movement of the gauge to see that it works, but no more.
As for sealing the sending units, it's better not to use anything to seal them at all, if possible.
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Fleet Owner
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From: Lake Tahoe, Nevada
Leaving the gauge grounded for an extended period, can cause damage to the gauge. It won't fry it, but it can cause it to read innacurate, by pushing the gauge past it's tolerances. IE: way beyond it's hot, or Full, or High mark.
I was always taught to ground it just enough to check movement of the gauge to see that it works, but no more.
As for sealing the sending units, it's better not to use anything to seal them at all, if possible.
I was always taught to ground it just enough to check movement of the gauge to see that it works, but no more.
As for sealing the sending units, it's better not to use anything to seal them at all, if possible.
All that deflects the needle is an induced magnetic field. Won't hurt a thing.
Posting Guru
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From: Niceville, FL.
Unlike most meter movements of the magnetic type (D'Arsonoval), Ford gauges use a heating coil wrapped around a bi-metallic strip. As the current through the heating coil increases, the heat causes the bi-metallic strip connected to the pointer to bend, increasing pointer deflection. This type of gauge responds much more slowly to changes in current than does a magnetic based movement. Slow response is desirable in an automotive gauge (especially fuel and oil pressure) so the gauge does not continuously fluctuate.
Fleet Owner
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From: Lake Tahoe, Nevada
Thanks for that additional input, Piffery.
I thought on the 80-86 trucks it was the style I described. Next time I have to open my dash I will examine that. In either case, I don't think there is any chance of damaging the gauge by grounding the sensor wire.
I thought on the 80-86 trucks it was the style I described. Next time I have to open my dash I will examine that. In either case, I don't think there is any chance of damaging the gauge by grounding the sensor wire.
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From: Virginia
I am not sure exactly what year, but sometime in the mid 80's they got away from the bi-metallic gauges. That's the year you will find no voltage regulator mounted on the cluster, and also the sending units for the gas tank read backwards compared to the older units.
Post Fiend
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From: Northern California
C \normal/ H
The needle deflection isn't supposed to get beyond the H mark on the gauge.
If you ground the gauge too long, this can happen...
C \normal/ H..... //*
*The "//" represents the needle.
Piffery explains how the gauge works quite well.
The bimetal strip attached to the pointer bends or warps out of shape causing innacurate readings.
When this happens to a fuel gauge it could read 1/8th of a tank when empty. Temp Gauge can read in the "MA" of normal, instead of in the "OR" portion.
I have a fuel gauge that has been damaged in this way, from a defective sending unit, grounding out.
However a slight bending of the pointer back to where it should be, usually fixes it fine.