Another "hot" topic

[Gordie Allen]

My bus has not made any long trips (>20mi) since I brought in home in Feb 2012.  I bought a new dash with all new gauges.  The temp gauge is electric of course, so I put a mechanical temp gauge in the engine compartment.  On the 20 mile drive I found the electric gauge read 120 while the mechanical gauge read 180.  So, I'm thinking more resistance (as in long wire) means lower reading.  Any suggestions on getting the right sending unit?

[Timkar]

Just wondering if you got this resolved? Possibly try using larger wire from rear to front gauge...
HTH....Tim

[Len Silva]

Wire size should not be a factor, 18 ga. should be plenty.

A good ground connection between the engine and gauge panel.

Be sure you have the proper sender.

Be sure you have a good source of voltage to the gauge.

Do not use any sealant when installing the sender.

Typically, any of those problems except the wrong sender will cause the gauge to read high, not low.

[chart1]

My electrical gauge in the dash reads about 15 degress lower than the mechanical in the engine compartment. The mechanical gauge is right on mine. 

[HB of CJ]

How good is the new dash board dedicated ground?  Is each gage dedicated grounded?  Engine to chassis ground? Sometimes some senders do not work right if the "hot" wire is too long--to little or too much resistance.  HB of CJ (old coot)

[Gordie Allen]

Thanks for the replies.  I bought a complete custom dash from Custom Instrument Panels (CIP), built to fit my 4104 dash pedestal.  The entire dash (8 gauges, 8 switches, back lit switches) was pre-wired, labeled and color coded from the builders.  I also got sending units for each gauge, so I assumed the gauges and sending units are matched.  I gutted the driver's panel and put in three 12 fuse blocks with 4 ground posts each.  Each fuse block has its own 8 ga. ground wire less than 6 in. in length.  I cleaned the threads in the thermostat with a round wire battery brush and installed with no sealer, tape, etc.  I guess I'll pull the  sender and call CIP to see if I have the right one or if it's defective.  Thanks for the input.
Gordie

[Len Silva]

You should be able to find a resistance chart online from the gauge manufacturer.  With that, an ohmmeter will quickly find the problem.  Here is one for VDO http://www.nsifleet.com/pdf/TemperatureResistanceChart.pdf