12 volt gauges on 24v bus

[Tom Y]

Would like to know if any one has seen these on a gauge before? The one is a 12v and the small button thing is on the hot wire. I am trying to see if I have 2 12v gauges, as I am going all 12 volt. Thanks To all.  Tom Y

[ol713]

Would like to know if any one has seen these on a gauge before? The one is a 12v and the small button thing is on the hot wire. I am trying to see if I have 2 12v gauges, as I am going all 12 volt. Thanks To all.  Tom Y

Hi;
   I have seen this sort of thing at  a street rod/custom shop.  They are used
   to drop the volts from 12vdc (upgraded) to 6vdc.  The purpose is to change
   a early street rod systrm to 12vdc and still use the origional 6vdc gauges and
   sending units etc.
                                   Good luck 
   

[Dallas]

My original oil and temp gauges had that on my bus.... but it's a PD4103 12V

[Jerry32]

You could but a zener diode in series with the hot lead to lose the extra volts. Usually 14 volts at the appropriate power rating for the current draw, Jerry

[Stan]

Depending on the type of construction of the guage, some will read correct over a wide voltage range and others will vary as the battery charges and discharges. Sensitive types have used a voltage regulator, either internal or external for many years. There are several different ways to regulate the voltage ecconomically. If you are just trying to regulate the output of a nominal 12 volt system into a 12 volt gauge then the zener diode works fine. If you are going from 24volts to 12 you need a fairly high power zener, but a 7812 package regulator does it easily.  Another approach is to make a power supply that feeds the entire dash with regulated voltage.

[Tom Y]

No I am going to all 12 volt.  The reason I asked is the one is marked 12 volt but the other I can not read. So I was thinking maybe it is also, and that is why these are on them. Thanks Tom

[Fredward]

Tom,
My 5A has those same devices on the water and fuel gauges. They seem to be step down resistors; at some point before i got it, someone built a new dash and must have used 12v gauges. It looks like 24v going in and about 14v coming out. They seem to work fine. I just replaced my fuel sending unit with the standard MCI sending unit and it reads accurately from empty to full (at least when i bench tested it).
Fred