55.2-59 Temp Gauge on a 59

[Oldroy61]

What does it mean if my electric temp gauge ,slowly climbs to hot with in the
first minute of starting? Faulty sensor or faulty gauge?
When I started having this problem, I installed a mechanical
gauge, and its works great and temps still cold of course.
So TIA and I hope some knows,
Thanks

PS I think sensor

[leegreen]

Probably a failed sensor or shorted wire. This must be aftermarket? The original clusters were all mechanical AFAIK

[Oldroy61]

Sorry to disagree, but both of my 59 clusters came with electric temps.
The wiring is new build, so it could be , but doubtful. Thanks

I don't think its the Gauge because it comes up slowly

[mr48chev]

This sure looks like an electric gauge to me.

Two things to consider, That may not be the correct sending unit for the gauge. Second, too much thread sealer on the sending unit will keep it from grounding and cause a wonky reading.

[dsraven]

so a stock 59 guage thats reading wonky?
inside the guage there 2 magnetic windings. one is a constant magnetic field and the other is a variable field depending on how much the sending unit grounds the sender wire. so, key on, cold engine, the constant magnet will draw the guage needle that way towards a cold setting on the guage because the variable magnet isn't getting much of a ground through the cold sending unit. as the sending unit warms up there is more ground potential given to the guage wire so the variable magnet becomes stronger and draws the guage needle away from the cold side of the guage.
with this in mind it makes sense that, short of a bad guage or sending unit, there is a problem with the wiring that goes to the sending unit. a quick test that I have done with the ANALOG guages is to disconnect the sending unit wire and see what the guage does, key on of course. it should pin at the cold setting or the hot setting, however the guage is made. if it does that, then the next test is to ground the sending unit wire and check the guage. it should pin the opposite way as when it was simply discoinnected. something that can change this is if you possibly have a poor engine or dash ground. assuming the starter whirls over like normal one would have to assume the engine has a good ground. the next place to look is where the guage cluster is getting it's ground from. since the dash lights etc will likely use the same ground as the guages it could be that once the engine is started and the cluster guages all start to need a ground at the same time, that the cluster ground is over taxed. this can be checked with a test wire, attached to a known good ground, that is touched to the cluster ground. if the cluster reacts with the guages or lights changing or getting brighter, then all signs point towards a poor cluster ground.
the cab should have its own dedicated ground wire from the battery to the firewall near the stock battery mount. if the battery was relocated then ensure there is still a dedicated ground to the cluster and cab in genera.
i usually run a ground cable, like normal battery cable size, from the battery to the frame and then to the engine. this can be a single cable with a joint in the area where the frame connection will be. or it can be 2 seperate cables, one to the frame, then one from the frame to the engine. it is also a great idea to make sure the metal under the ground connections is nice and clean and bright shiny metal. a lot of people will not pay much attention to the ground circuits but, instead, will spend a lot of time making sure the positive cables and connections are top notch. but, if the ground circuits are not as good as the positive connections then the ground circuits become the weak link.
sometimes i will use a booster cable, connected to the negative battery terminal only, to check for bad grounds. if there is some problem going on inside the cab, like a cluster issue or a heater motor thats slow, and the cable is touched against the cab and that seems to make the problem go away then one has to assume there is a bad ground to the cab. if your headlights are dim but they brighten when the booster cable is attached to the headlight ground wire or rad support, then one would assume there is a bad ground to the rad support where the headlight ground wire is usually screwed on.

[dsraven]

the test lead attached to a good ground like directly to the battery neg, or the booster cable trick, attached directly to the sending unit outer housing, would be a good indicator if that changed the guage reading.
another thing that it could be is something is possibly stealing power from the bat pos side of the guage making the permanent magnet less strong. a quick check with a multimeter on the gauage might be in order. disconnect the sender wire so the circuit is open on the other side of the guage
if you have lots of wire laying around you could wire the guage independently of the truck. so a wire from the battery pos to the guage pos side. then another wire from the sending unit directly to the other side of the guage where the sending unit wire used to be connected. then start the truck and see what the guage does. this would require ensuring the guage is fully disconnected from the cluster power supply and original sending unit wire

doesthe rest of the cluster, including lighting, work properly? nothing different about the cluster, like it is a totally stock cluster with no add on stuff or LED bulbs etc?