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"54 Temp gauge problems

Started by timer2, May 24, 2021, 06:03:22 PM

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timer2

My temp gauge has been slowly getting lower readings the last couple years. It started out about midway on the gauge and has now stopped at the cold mark...wouldn't come up any higher. So I removed the old sender and bought one from O'Reilly's, aTS6 standard motor part, installed it, and now it appears that for a couple seconds the gauge reads correct but then slowly drifts up to the H position. I've also replaced the thermostat just cause it was cheap. My IR gun reads about 170 degrees so everything is cooling, I just don't get the slow drift towards hot on the gauge. Any help is appreciated.  T. Irvin

J. Gomez

Quote from: timer2 on May 24, 2021, 06:03:22 PM
My temp gauge has been slowly getting lower readings the last couple years. It started out about midway on the gauge and has now stopped at the cold mark...wouldn't come up any higher. So I removed the old sender and bought one from O'Reilly's, aTS6 standard motor part, installed it, and now it appears that for a couple seconds the gauge reads correct but then slowly drifts up to the H position. I've also replaced the thermostat just cause it was cheap. My IR gun reads about 170 degrees so everything is cooling, I just don't get the slow drift towards hot on the gauge. Any help is appreciated.  T. Irvin

Terry,

If you do a search on the site you will find a few older post related to this particular issue.

Here is one with several links to similar post -> http://forums.cadillaclasalleclub.org/index.php?topic=152504.0

The problem is the temp sender has the wrong resistance for the gauge to read the correct temp. The only solution would be to find an OEM which is $$ or add a resistor in series to match with the gauge.

Good luck..!
J. Gomez
CLC #23082

timer2

Thanks J.  I had found a few threads on the subject but nothing on the slow movement of the needle to H after registering the correct temp initially. I have a 10 ohm 1w resistor somewhere in the garage that I'll put inline today. I bought 2 from Digi Key a few years ago when doing the gauges on a Hudson and only needed one. If it settles the needle anywhere between C and H that will be my new 180 degree mark and give me a staring point to add or subtract resistance. I'll shoot for the center gauge mark as 180. Thanks again      T. Irvin

J. Gomez

Quote from: timer2 on May 25, 2021, 08:26:10 AM
Thanks J.  I had found a few threads on the subject but nothing on the slow movement of the needle to H after registering the correct temp initially. I have a 10 ohm 1w resistor somewhere in the garage that I'll put inline today. I bought 2 from Digi Key a few years ago when doing the gauges on a Hudson and only needed one. If it settles the needle anywhere between C and H that will be my new 180 degree mark and give me a staring point to add or subtract resistance. I'll shoot for the center gauge mark as 180. Thanks again      T. Irvin

Terry,

A slow movement of the gauge while the engine is warming up could be cause by a few things, sticky needle, poor ground at the gauge, etc.

The gauge will get the ground from the metal case and there could be some corrosion built between the gauge frame and the case which requires cleaning. I know removing the gauges from the instrument cluster is a pain >:(

If you have other resistor handy you can test the function of the gauge by adding about 400ohms or 200ohms on the green wire to ground which is the range of 150 to 212 degrees temp.   ;)

Good luck..!
J. Gomez
CLC #23082

timer2

Thanks again J, I found and added the resistor...it's a 10ohm 10w resistor not a 1w....the needle didn't drift upward at all with the ignition on, engine off. I started the car and the needle slowly drifted to H (took about 5 minutes) but then settled down to the 3/4 mark with the engine at 165 degrees at the thermostat. I'm not sure how important the wattage ratings are compared to the resistance ratings of these resistors but I'm thinking 10 w is overkill. I'll be ordering a few resistors from Digi Key in varying strengths as it appears I'm somewhat on the right path. With the engine cold (60 degrees) I measured 24 ohms through the new sender...when the engine cools enough I'll measure again and maybe I can come up with some type of ratio that I can use to determine the Ohms needed to get me closer to the center mark. BTW, when I shut the engine off and turned the key back on, the gauge went almost to the center mark, stayed there for 30 seconds before drifting up to the 3/4 mark. T. Irvin

J. Gomez

Quote from: timer2 on May 25, 2021, 10:11:10 AM
Thanks again J, I found and added the resistor...it's a 10ohm 10w resistor not a 1w....the needle didn't drift upward at all with the ignition on, engine off. I started the car and the needle slowly drifted to H (took about 5 minutes) but then settled down to the 3/4 mark with the engine at 165 degrees at the thermostat. I'm not sure how important the wattage ratings are compared to the resistance ratings of these resistors but I'm thinking 10 w is overkill. I'll be ordering a few resistors from Digi Key in varying strengths as it appears I'm somewhat on the right path. With the engine cold (60 degrees) I measured 24 ohms through the new sender...when the engine cools enough I'll measure again and maybe I can come up with some type of ratio that I can use to determine the Ohms needed to get me closer to the center mark. BTW, when I shut the engine off and turned the key back on, the gauge went almost to the center mark, stayed there for 30 seconds before drifting up to the 3/4 mark. T. Irvin

Terry,

The wattage is the amount of dissipation in this case a resistor can handle, so 10W is "way too" overkill for just this application, a 1/2W should suffice.

If you had a chance to read the other post the replacement sender TS-6 would have a resistance range of;
150º = 318Ω
180º = 227Ω
190º = 205Ω
212º = 155Ω
While the OEM has;
150º = 380 Ω
180º = 275 Ω
190º = 255 Ω
212º = 200 Ω

So if you place a resistor of around 50-60 ohm it should be fine, again these are just approximately.
J. Gomez
CLC #23082

timer2

Again, thanks J     With the thermostat housing at 160 degrees I get 163ohms through the sender. Doesn't seem to line up with the numbers posted for TS-6 but I'm sure either I'm missing something or the variables via the sender and my own process for taking the readings is off. I've ordered 3 different chassis mounted, wire wound resistors so I can hone in on the closest to being accurate.  T. Irvin

bcroe

Quote from: J. Gomez on May 25, 2021, 11:56:47 AM
Terry,

The wattage is the amount of dissipation in this case a resistor can handle, so 10W is "way too" overkill for just this application, a 1/2W should suffice.

If you had a chance to read the other post the replacement sender TS-6 would have a resistance range of;
150º = 318Ω
180º = 227Ω
190º = 205Ω
212º = 155Ω
While the OEM has;
150º = 380 Ω
180º = 275 Ω
190º = 255 Ω
212º = 200 Ω

So if you place a resistor of around 50-60 ohm it should be fine,
again these are just approximately. 

By those numbers a 47 ohm series resistor should be very
close, but 163 ohm at 160 F sounds like a bad sender.  Bruce Roe

timer2

I always assume that a replacement, non OEM part, will not perform like the original. It seems to be the way of the hobby. When I'm done, I'll know what the temp is according to the parameters that I've set for the gauge marks. Might not be perfectly accurate but I'll get close. The upside is the car got a new thermostat and new antifreeze AND I kind of enjoy the challenge of getting the sender to work and the challenge of getting the little bugger out. T. Irvin

timer2

Update-after experimenting with a couple resistors, I put in a 30ohm 1w resistor and the gauge reads a couple ticks before the center mark when the engine is fully warmed up with my IR gun reading 178 degrees at the thermostat housing. I will leave it alone now.  Thanks guys     T. Irvin

Hillbillycat

Did you check if the needle isn´t sticky inside your gauge?
I had a fuel gauge that constantly gave erratic readings which turned out the oil on the needle pivot had gone sticky. Cleaning did the trick. Needle pegs up to "F" in a wink now.