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Gauge problems
https://slantsix.org/forum/viewtopic.php?t=12227		 Page 1 of 1
Author:  BluefishBud [ Mon Mar 14, 2005 1:26 pm ]
Post subject:  Gauge problems
temp gauge stopped working on my 78 cordoba. with the front face of the instrument cluster removed, i touched the test light tip on the temp gauge wire on the multiconnector, which is still plugged in. the test light will blink and the guage needle will move. but when i withdraw the light away, the needle will park itself.
should i suspect a faulty voltage limiter? the reason is, i also touched the light on both copper pinchclip terminals (which the threaded posts on the back of the guage slide into) with the gauge removed. one side lights but blinking, the other does nothing. after looking at the picture diagram of the printed circuit board in my FSM, the side that is not lighting up is tied in to the 5-volt terminal on the voltage limiter. :?

any assistance appreciated
Author:  K.Beard of TMC [ Mon Mar 14, 2005 1:45 pm ]
Post subject:  gauge problem
I think your gauge and limiter are fine.

Your 5V limiter has a +12V in, ground, and +5V (actually pulsing DC that averages to around 5V) out connections. If you get pulsing DC at the connector to the sensor and the needle reads, your problem is not the gauge and not the limiter - you've an open between there and the sensor, a bad sensor, or a bad engine ground.

With the gauge removed, there should be no power on the sensor side, but the +5V on the input side.

Touch the light to the connector right at the sensor and ground to the block - if the light blinks, your sensor is bad or the connection to it is bad. If it doesn't blink, you've got an open somewhere.

A typical test light will make a Mopar gauge read ~1/8-1/4 way or so. The gauges are easily burned out, so do not short the input out.

The thermistors used in Mopar temp sending units are both cheap and reliable -I personally have never seen one fail, so I would check carefully for an open in the wiring.
Author:  Guest [ Mon Mar 14, 2005 3:29 pm ]
Post subject: 
Quote:
Touch the light to the connector right at the sensor and ground to the block - if the light blinks, your sensor is bad or the connection to it is bad.
i did this test after changing to a known good sending unit. still blinks and still no needle. just for "S&G'S" i walked over to my truck and ran the engine and touched the test light on that sending unit connector. the light blinks with the temp gauge operating fine on the truck.
im stumped :?
Author:  K.Beard of TMC [ Tue Mar 15, 2005 3:41 pm ]
Post subject:  Re: sensor
Somewhere there is a bad connection; if the test light flashes while connected to the sensor, current is flowing and the gauge should read at least part way.

I suspect you've got a flaky connection right there - try to connect the light between the sensor lead and the sensor - it should be dim with the sensor cold, and brighter w/ the sensor hot.
Author:  BluefishBud [ Thu Mar 17, 2005 4:40 am ]
Post subject: 
Found the problem:
The temp gauge wire on the multiconnector was not making contact with the printed circuit board when plugged in and refused to do so after several attempts of jiggling with the wire. I removed the cluster assembly and dropped a bead of solder on the copper connection on the circuit board. I then put the cluster assembly back in and plugged the multiconnector back in. The plug was now a little harder to plug in, due to the solder bead, but the temp gauge is now working. Until I find a replacement printed circuit board, this fix has to do for now.
Thanks for everything :)
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