63 Temperature gauge test methods needed

[Todd L.]

Good morning guys,

I am 99% finished with the restoration on the 63 Split, and the last issue I have found is the water temp gauge doesn't work. Is there any way to test the sending unit to see if it may be bad? That would be much easier than pulling the entire gauge cluster out to replace the gauge. Any thoughts?

Todd

[Harry S.]

Re: 63 Temperature gauge test methods needed

Todd, did you put any sealer on the sender when you installed it? If yes, pull the sender and remove any traces of sealant. If no, put in a cheap sender to see if the gauge moves. Also, check the connections on the back of the gauge. Do the other gauges work, If none of them work you may have a ground problem.

[Gary B.]

Re: 63 Temperature gauge test methods needed

Todd,

Have you read thru the temperature sender documents in the sticky threads section of the TDB? For example,

https://www.forums.ncrs.org/attachme...4&d=1499168130

[Larry M.]

Re: 63 Temperature gauge test methods needed

Hookup a multimeter (Fluke) to the sending unit. One connection to sending unit top pin and the other connection to a GOOD engine ground. Use an IR run to also shoot the temperature of the sending unit.

Take temps and ohms at room temp, and then at about 4-5 points up to final engine operating temperature.

Then compare these ohms vs temperature readings to actual GM/AC Delco curves. I can provide info if you cannot find it in the archives. It has been posted before.

Here are GM specs per Ken Anderson of K&B Products:

100F temperature........350 ohms. (340 ohms)
180 F..........................105 ohms (128 ohms)
210 F...........................76 ohms. (79 ohms)
240 F...........................72 ohms. (68 ohms)
250 F...........................52 ohms (51 ohms)

Plot these on graph paper to read intermediate valves and temperatures not shown.

Wilcox website also has very good info on this as well. The values above in () are from Wilcox

[Todd L.]

Re: 63 Temperature gauge test methods needed

These are some great suggestions, thanks for the information specs, I will check this out when I get a chance.

I did use Teflon tape to seal the threads on the sending unit.

All other gauges seem to work, except the ammeter, it always stays at 0. I may have a problem with it too...

[Kent S.]

Re: 63 Temperature gauge test methods needed

If I remember correctly, if you take the wire to the gauge off the sender and ground it (with the key on) it should peg the gauge. If not the gauge is bad or the wire has an open break.

[Gary B.]

Re: 63 Temperature gauge test methods needed

One thing to consider when using an IR gun is the emissivity of the target object. The emissivity is 1.0 for a perfect, dull, black body. Some guns allow you to input an emissivity value, but of course to do that you need to know the emissivity value. Here is a list of emissivity values for lots of things:

https://www.thermoworks.com/emissivity-table

[Todd L.]

Re: 63 Temperature gauge test methods needed

That should be easy to check, I will try that first

[Gary B.]

Re: 63 Temperature gauge test methods needed

…

I did use Teflon tape to seal the threads on the sending unit...

If you read the temperature sending documents in the sticky postings, you’ll see that John Hinckley and someone else state, based on actual use and a multi-meter test, that a judicious use of Teflon tape to serve as a thread lubricant (over the leading threads), not a sealer, does not cause a significant problem. Just don’t overdo the tape. Or compare tape to no tape conditions to rule out a problem from excessive tape.

Gary

[Larry M.]

Re: 63 Temperature gauge test methods needed

One thing to consider when using an IR gun is the emissivity of the target object. The emissivity is 1.0 for a perfect, dull, black body. Some guns allow you to input an emissivity value, but of course to do that you need to know the emissivity value. Here is a list of emissivity values for lots of things:

https://www.thermoworks.com/emissivity-table

Notice the values for brass, highly polished (0.03) vs oxidized (0.61). So, if the IR gun says the temp is 210, but the emissivity value isn’t taken into account, who knows what the temperature really is. That is why a boiling water test of a temperature sender is useful.

I would wager that many IR gun values give the user a false sense of accuracy unless the emissivity is taken into account. I would trust an IR reading taken from a dull, black radiator hose, before I’d trust the reading from a new, shiny, brass temperature sender. Unless a reasonable emissivity value is used for the latter.

Gary

Gary:

Agree that removing sender and checking with hot and boiling water and a thermometer is a very good idea. Same with new thermostat. . That way is much more accurate.

Also agree 110% regarding IR guns and the emissivity. When I check engine temp on my 327/350 HP car (dull aluminum manifold) I focus on the intake manifold water passage where the sending unit is located. Even with my high-end industrial rated IR gun, I generally get a mix of the sending unit and the intake manifold around it. In my case, I allow the engine to get to operating temperature with coolant circulating and then compare ohm and temperature readings versus the thermostat design temperature that is installed.........in my case 180F.

The main reason I suggested taking a few readings from room temperature to operating temperature was more to see that the sending unit was responding like designed...........but not focusing so much on the accuracy of these readings. Use the one with engine temperature stabilized compared to thermostat design temperature. After all, that is the one we normally see just about all the time.

Gage operation can be checked by buying and installing various resistors in line with the sending unit wire to the temperature gage to check calibration.......but again, it will be approximate and not like a real instrument calibration and test rig setup. But a final resistor can be installed and used to get the gage to read accurately at normal operating temperature.

Back in the day, the temp gage was approximate at best anyway. Many cars only had a "light". But the gage is good for showing changes and trends.

Larry

[Todd L.]

Re: 63 Temperature gauge test methods needed

Well, I checked Ohms on the car cold and they were 758, which appears high. I checked resistance on the green wire from the sending unit to the gauge and it Ohms at 000, so it is good. I grounded the green wire out and the gauge didn't move, so it appears the gauge is bad and I will have to pull the gauge cluster out....

[Jimmy G.]

Re: 63 Temperature gauge test methods needed

758 at room temp is about normal for a good unit I have 10 - 20 and they are all around that number at room temp

[Todd L.]

Re: 63 Temperature gauge test methods needed

Ok, thanks for that info

[Michael G.]

Re: 63 Temperature gauge test methods needed

Remove the sender. Thoroughly clean the threads of both the sender and the tapped hole in the intake. Make sure you see bare, clean metal. Apply Teflon tape or sealer to the threads that were previously engaged in the manifold, but be careful to leave the first two completely-formed leading turns (the ones that will enter the manifold first) bare. Screw the sender back into the proper torque. You should now have good sealing and an adequate ground.

[Thomas S.]

Re: 63 Temperature gauge test methods needed

I have to replace the temp gauge on my 63. I did not pull the cluster yet but went through that torture 5-years ago. I have a NOS gauge (6400616) that I will test. The article that appears on the TDB and is referenced in this thread, mentions a 90-ohm shunt resistor which I don't remember seeing when I rebuilt the cluster nor is it on the 63 gauge. That article was referencing a 65 gauge. The question whether of not the shunt resistor was applicable to 63?