47-55.1 Temperature Gauge not working

[hogfarm]

After my almost 2year rebuild modifying of my 54 chevy things are done. So was going to take a test drive, and saw that my temperature Gauge was not working. Noting new in the cab, I did install a 383 stroker with the old manifold sender.

[fauXGT]

Shouldnt make a difference with the same gauge and sender. How is the ground on the sender? Sometimes too much sealer creates not a good connection on the ground side. Take a volt/ohm meter and check ohms from metal of sender to a good ground like an exhaust bolt with the sender still in. Should be close to zero ohms. Mine has continuity checker, so it beeps at me, so I can check all the senders I've installed. Newer sender have a 2 wire connection, so no ground from the block needed.

[fauXGT]

New in the cab, as in like an aftermarket, or factory.

[leegreen]

A factory gauge with a capillary tube? Maybe the tube got damaged

[mr48chev]

I'm thinking that FauXGT probably nailed it spot on. Too much sealer acting as an insulator. A quick test would be to use something even jumper cables or a screwdriver to ground the housing of the sender and see if it works.

[dsraven]

if its the rignal capilliary tube sender then it probably got pinched or bent how it didn't like to be bent so it leaked out the contents of the tube and now it's just an ornament. sad but possibly true. if it's electric first heck thw fuses and then check for the bad ground connection, mentioned above, and then check the plastic or bakelite portion of the sender for cracks or deformity that can easily happen during the removal and insatllation of the sender. another way to test an electric gauge is to simply ground the wire at the sender unit, since the sender is simply a variable ground source for the gauge.

[fauXGT]

If he has put in a 383, I guess it's a new aftermarket?
The wiring harness I'm currently installing has a single wire that goes from gauge to sender, bypassing any fuses. Only fuse in the link is the Ign+ to any gauges that require batt. One fuse. I'm using the new sender from the Bosch gauge that I've put into the factory pod, but we need to find out what he has installed.

[fauXGT]

And was messing with it today, trying to figure out to get two different temp senders connected. One for Bosch gauge on dash, and one for Sniper EFI. I'm gonna tap a new hole into the intake for one tomorrow, but will check continuity once done

[hogfarm]

Not to much is stock on my truck, and I have had the truck for a long time. The gauges in the dash were made by Tri-Tech. That company is no longer with us. I can jumper the send to ground and the gauge will bounce.Ohm meter in the morning. How many Ohms should I be looking for as the trucks heats?

[Accelo]

You can easily check the gauge and the wiring. Disconnect the wire from the temp sensor(should be 1 wire connector) and ground the wire. The gauge should go through the full range of motion when you ground it. All the way hot when grounded. That's how the sensor works, as it gets hotter, the resistance changes. If the gauge goes all the from cold to hot when you ground it, it more than likely is a bad sensor. As a caution get the AC-Delco sensor if you believe it is defective. Aftermarket sensor's resistance varies all over the map and because of this the readings can be way off.

[dsraven]

the sender really needs to match the gauge as sensors are not all the same in how they manage the amount of ground provided at a specific temp. the gauge is simply a needle balanced between 2 electrically operated magnets. one magnet has a constant amount of magnetism on one side of the needle and the one on the other side of the needle has a variable amount of magetism which is dependent on the amount of ground given by the sender. with he sender wire disconnected the constant magnet will draw the gauge needle all the way to that side becaue there is no magnetic draw on the variable magnet. if the sender wire is grounded then the variable magnet will have it's magnetism maxed out so it will draw the needle all the way that direction. it makes sense, then, that the sender needs to match the gauge or else the reading on the gauge will not be correct. with the incorrect sender the needle may move through a range but may not match the actual temp of the engine.

[mr48chev]

Just use something to ground the sender housing (sender it's self not the adapter) to clean bare metal on the engine and that should tell you if you have a ground issue due to too much sealer.

[hogfarm]

Got it figured out, there were 2 wires to the sender, only need the 1

[fauXGT]

The sender on the right of the filler is the 2 wire for the Sniper EFI not needing a frame ground, and the one on the left with the cloth wire is the single wire for the dash gauge. I drilled and tapped the smaller single one today, checking the ground continuity after sealing.

[leegreen]

Possibly useful in situation like fauxgt shows, GM part number # 12551708 is a temp sensor with 3 wires, 2 provide the varying voltage style output for engine control computer to read, the 3rd is a resistance to ground for a variable current to drive traditional electric temp gauge like dsraven described above.

Useful part for EFI swaps to keep a temp gauge in older cluster working. Voltage range has to match computer expectations, that part number should work for LS OEM computers. Current range may not be accurate on gauge face, but if it gives you a visual for normal operating temperature that is all you need