Which guage to trust or How many sending units can there be?

[ssvett]

Yep, Still on the silver 69. The mechanical guage reads 180 all the time(a little higher after shut off). The original guage reads 250 shortly after starting. The car is not hot!!!!!!This original guage reading has been tested with 2 guages and 3 sending units. The car is not hot!!!!!!!I checked the continuity of the gnd, and the temp sending unit wire and the voltage. All seem to be normal. The resistance on the Temp sending unit wire raises as the car gets warm(as it should)I'm not sure though how high the resistance should be?????But it is the same on both units????????I'm sooo confused......BTW, just a small bit of information for those of you at home, wait for the car to cool down before attempting to change the sending unit........That stuff is hot.........even at 180 or so........I bet I won't try that again for awhile..............Steve

 

[80convertible]

Steve,

I really know how frustrating gauges can be. I finally got my volt gauge working after a month of troubleshooting. One thought that is never discussed is the resistor on the back of the gauge. You won't find any info on these in any of the books. While working on my gauges I realized that this little resistor on the back of each gauge is critical for proper reading. In fact, if the resistor is not on the back of the volt gauge it won't work. Furthermore, my oil pressure gauge would not read correctly until I secured the resistor better. You may want to clean the contacts on the resistor to the temp gauge with a pencil eraser. Again there has to be a good contact or the gauge will read incorrectly. Also, has the gauge always been reading hot or is this a new problem? I ask because someone could have installed the wrong resistor on the gauge. I saw this on a gauge cluster recently. I am not sure about your 78 but my cluster resistors are all color coded to each gauge. Just a suggestion as this cured my problem.

Regards,

Jim

 

[Nut]

Steve,

If the "colors" on the resistors are banded stripes, they determine the value of the resistor and can be looked up in any electrical hdbk. I'm sure I've got one here at work if you need the bands deciphered. If they are solid colors, they (might) have the value screened on the part. You'll need some type of magnification device to see it. If not, put it on a Multimeter or old style VOM meter and read the values. If you have to replace them use a MIL-SPEC quality resistor from an Electronics supply store (not Radio S). They'll only be moderately more expensive but substantially more reliable.

........ Nut

 

[Fast Ed]

colors

I'm sure twigett knows the phrase, some words were changed to avoid the dreded *

"Bad Boys Rob Our Young Girls Behind Victor Garden Walls" "Get S Now" First letter is the color valued 0 1 2 etc. Gold Silver Neutral is the value 10, 100 1000 power

Red black one end and the other end Gold = 20K

I'm fairly sure but it's been several years since the design days and chips took over and the advent of the
black box theory.

 

[ssvett]

The Final Chapter(I hope)

Well, here is what the final verdict is. After 3 sending units, 2 guages, and 1 mechanical guage(that I trusted all along) It is cured. We apparantly had the wrong sending unit, 2 of these came from the local parts store and one from Chevy, all read Hot. We had a 72 in that we were measureing for some bigger AFR heads so I thought I'll just try that one. I know it works and it looks a little different. It worked now all I got to do is find out where it came from....... The silver 69 BB is a hoot to drive but the owner is comming up from Memphis tommorrow to take her home.............I'll be sad, But I will be happy with the check........Steve

 

[SSAutoJR]

ME TOO !!!!!

Tomorrows pay day, oh no wait.... when is pay day? ....I cant remember.
Just kidding
good night DAD,
Sam

 

[1yy07]

temp gauge

SSVETT If this is a GM gauge send it to Corvette Clocks by Rodger 901-664-6120 1-800-752-3421 orders only. he does a great job!

 

[ssvett]

1yy07, And everybody else, thanks for your replies, help and incouragement. The problem came down to the wrong sending unit. And yes Roger's does do a very good job on guages. I send mine to a guy down south now, but I used to send them to Rogers, and if this guy quits working on them for me, I will go back to Rogers........Thnks again......Steve