Stewart Warner Temp Gauge, Single Wire??

[hotwls13]

I haven't ran the truck for more than 3-5 minutes at a time since I bought it a couple months ago. Mostly because it barely had any gas and I was in the middle of the tank relocation. Now, because I still haven't gone through the running gear (other than changing rear gear oil, checking engine oil, coolant and trans fluid levels).

I'm going to assume my factory Temp gauge doesn't work (since previous owner added a Stewart Warner temp gauge). Temp really hasn't gotten that high (somewhere a bit above 100) but honestly the truck hasn't ran for long and I wasn't watching the temp that closely. I was also worried thermostat could be stuck and cause truck to overheat??

My 2 questions are:

1. What are the chances my original gauge works and just needs a new sender or proper wiring (or both)?

2. The Stewart Warner only has a single large black wire coming out of it. Does that sound right?? And where should that black wire be going??

Thanks,

I'm a newb to all of this, but I'm willing to learn.

[ray_mcavoy]

Originally Posted by hotwls13

1. What are the chances my original gauge works and just needs a new sender or proper wiring (or both)?

Yes, there is a good chance that the original temperature gauge is okay and simply needs a new sender and/or wiring repair.

You can do a quick check by unplugging the wire from the temperature sending unit and temporarily jumpering the wire to ground. Turn the key on and watch the gauge. If it pegs to the hot side, the gauge and wiring are most likely okay and replacing the sending unit will get it working again. But if the gauge doesn't move there is a problem with the wiring (often a bad connection somewhere) or less likely the gauge itself is bad.

Originally Posted by hotwls13

2. The Stewart Warner only has a single large black wire coming out of it. Does that sound right?? And where should that black wire be going??

That is probably a mechanical temperature gauge. In which case that black "wire" is actually a capillary tube that connects the gauge to a temperature sensing bulb. The sensing bulb fits into a threaded bushing adapter that in turn screws into a coolant port on the engine. A hollow threaded nut (that is pre-installed onto the gauge/tube/bulb assembly) secures the bulb to the adapter bushing. When new, theses gauges usually come supplied with 2 or 3 of those adapter bushings to fit various engines.

[hotwls13]

Originally Posted by ray_mcavoy

Yes, there is a good chance that the original temperature gauge is okay and simply needs a new sender and/or wiring repair.

You can do a quick check by unplugging the wire from the temperature sending unit and temporarily jumpering the wire to ground. Turn the key on and watch the gauge. If it pegs to the hot side, the gauge and wiring are most likely okay and replacing the sending unit will get it working again. But if the gauge doesn't move there is a problem with the wiring (often a bad connection somewhere) or less likely the gauge itself is bad.




That is probably a mechanical temperature gauge. In which case that black "wire" is actually a capillary tube that connects the gauge to a temperature sensing bulb. The sensing bulb fits into a threaded bushing adapter that in turn screws into a coolant port on the engine. A hollow threaded nut (that is pre-installed onto the gauge/tube/bulb assembly) secures the bulb to the adapter bushing. When new, theses gauges usually come supplied with 2 or 3 of those adapter bushings to fit various engines.

OK, I'll give that a shot. I'll try to trace the wire(s) also.

Been hot as heck lately (100 degrees plus last couple days) so I haven't been working on the beast much.

[hotwls13]

Well I didn't have time to figure out what wire(s) are/were supposed to go to factory temp gauge.

I did however snap some pics of the SW gauge and where the one black wire/tube goes. From the description you gave I'm guessing mechanical gauge? Looks like it's leaking. :/

And I'm guessing the empty post on the back of the gauge would be to power illumination?

[ray_mcavoy]

Originally Posted by hotwls13

Well I didn't have time to figure out what wire(s) are/were supposed to go to factory temp gauge.

I did however snap some pics of the SW gauge and where the one black wire/tube goes. From the description you gave I'm guessing mechanical gauge? Looks like it's leaking. :/

Yes, that is a mechanical gauge. And yeah, it does look a bit damp around where it screws into the engine so it could be leaking a little.

If you remove the SW gauge and hook the stock temp gauge back up, it will use that same hole for the sending unit. And be sure to route the sending unit wire as far away from the exhaust header as possible. The capillary tube on the mechanical gauge is a little more forgiving but might cause the gauge to read a bit higher than normal being that close to the header.

Originally Posted by hotwls13

And I'm guessing the empty post on the back of the gauge would be to power illumination?

Yes, that empty tubular hole in the back of the gauge would accept a small bulb & socket for illumination.