Temperature Gauge
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Senior User
Joined: Oct 2012
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Temperature Gauge
1970 F250, 360
This just started happening. When I start the truck from cold, the gauge reads cold as it should. Then after a few minutes, as the truck warms up, the gauge starts to climb, but goes a little faster than normal and all the way until it's pegged. Often, when I give it some gas, it drops back down to the normal range, only to return to pegged soon there after.
Any ideas? The truck is not actually overheating, and has a new thermostat.
This just started happening. When I start the truck from cold, the gauge reads cold as it should. Then after a few minutes, as the truck warms up, the gauge starts to climb, but goes a little faster than normal and all the way until it's pegged. Often, when I give it some gas, it drops back down to the normal range, only to return to pegged soon there after.
Any ideas? The truck is not actually overheating, and has a new thermostat.
Fleet Mechanic
Joined: Oct 2005
Posts: 1,369
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From: Gainesville, GA
Many, many, many years ago I added mechanical oil pressure and temperature gages to my truck. I cut the right size holes in the dash, on either side of the speedometer, and installed them. I'll post pictures if needed.
Fleet Mechanic
Joined: Oct 2005
Posts: 1,369
Likes: 7
From: Gainesville, GA
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Upon further inspection I noticed that my coil wire was resting on the sending unit wire. I thought this might explain why the gauge would sometimes fluctuate with large changes in RPM. It has now been rerouted and my gauge no longer pegs hot when the truck warms up. However, now the gauge only moves slightly above cold after warm up. Could the coil wire have fried something?
Logistics Pro
Joined: Mar 2005
Posts: 3,771
Likes: 80
From: tujunga, calif
Are you sure the engine has reached max temp? I know mine takes forever to do that even with a 190 thermostat. Take the wire off the sending unit and ground it to the engine, the gauge should go to the hot side. If it does the gauge is probably good and then sending unit may not be.
Fleet Mechanic
Joined: May 2001
Posts: 1,396
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From: Cupertino
I am an electrical engineer. I cannot come up with any sensible reason wherin a coil wire in a high impedance circuit could couple into a dc circuit like an electrical gauge. Certainly not to make the gauges go nuts or with the temperature dependance that you describe.
Do you hear any engine-rev-dependent noise in your radio?
Do any other gauges flare when your temperature gauges flare? (CVR).
As above, I suggest you replace the sender.
Do you hear any engine-rev-dependent noise in your radio?
Do any other gauges flare when your temperature gauges flare? (CVR).
As above, I suggest you replace the sender.
