55' speedo, 12v system, 6v gas gauge, help me

The sender unit for gas guage is the same part for either 6 or 12 volts. For the guages if you have the silver face Willys script guage cluster there should be an little sqaure box mounted to the back of it, thats the instrument voltage regulator. While they were designed for operation on 6 volts rumour has it they will operate quite well on 12 volts as well so you should be safe. To check it there should be 12-14 volts on the input & ~5 volts on the output. If you test it dissconnected from the dash make sure you have use a clip lead to connect the guage cluster to a good ground or the regulator won't regulate therby releasing the smoke from the internal bitties & as we all know once the smoke escapes from them bitties don't work anymore .

H.


H.

 

You can get a voltage drop resistor from any of the Jeep parts houses to use the 6v gauges in a 12v system. I got mine from JC Whitless, it worked just fine once it finally arrived from Bangalore, India or sumsuch place (~ 5 weeks).

 

A regulator reduces the battery voltage to a level that the guages can safely operate at. On early speedo/guage clusters like were used in '55 the regulator is, as I stated. a small box mounted on the back of cluster. It has two termiinals, one that gets battery voltage from the ignition switch, the other feeds the regulated, i.e. lowered, voltage to the guages. The regulator also needs to have an electrical connection to ground, normally just being screwed to the speedo case does it as long as the speedo is properly mounted to the dash. If the ground connection is lost the regulator doesn't work & feeds the full 12 volts from the battery to the guages. The guages were designed to operate with a voltage of about five volts, feeding them 12 volts can destroy them very quickly. If you remove the speedo from the dash for testing then you need to restore the ground connection, usually most people use a clip lead which is simply a length of wire with an alligator clip on each end.

As I stated earlier the regulators used on the early clusters were designed for an input voltage of around 6 volts but people have found that they will also work with a 12 volt input without burning up.

Hope that helps,

H.