bad sending unit

[macibell111]

I have a 12 volt system in my M and put an aftermarket 12 volt sending in which lasted 2 days ,I am putting in an original 24 volt sender in ,my question is do I need some kind of resister for it in order for it rto work,what do I need to do to make it work any help would be very much appreciated thanks jack

[w30bob]

Hi macibell,

What exactly went wrong with the sender? Is it reading open.....or does moving the float not change the resistance? They're pretty simple devices, so there's not much to go bad. The sender itself doesn't care what the voltage of the system is, it's only changing the resistance of the circuit. The gauge cares what the system voltage is because it's designed to operate in a specific voltage range.

regards,
bob

[tbone1004]

with what Bob said,
Assuming this is the fuel sender although it is valid for all senders, you have to find out what the gauge wants for input voltage for full and empty and get a sending unit compatible with that gauge otherwise it will never work. Why do you think going to a 24v unit with a 12v gauge is a good idea? If you're asking what you need to do to get that sender to work you probably don't understand the electrical circuits well enough to successfully adapt it. You also have to find out why the 12v sending unit shat the bed, if it was a wiring error or what.
http://www.dodgepowerwagon.com/best/m37 ... stance.php
Here are the stock sender and gauge resistance requirements.
Note the 30ohm full 0 ohm empty.
The universal senders are nowhere near that resistance levels, so you're going to have one helluva time getting that system to work. You're far better off just going to one of the gauge manufacturers and getting a new gauge with their sending unit and calling it good.

[JimC]

With an original sender,you need to find a 12v gauge whose voltage will change from 0 to 14 with a 30 ohm change in resistance.

[pwrwagonfire]

With an original sender,you need to find a 12v gauge whose voltage will change from 0 to 14 with a 30 ohm change in resistance.

Good info!

-T

[JimC]

Pre 65 GM's used sending units that were O ohms empty and 30 ohms full. The pre 65 GM gauges were compatible with that, so should also be compatible with the stock M37 Sending Unit (which is also 0 ohms empty and 30 ohms full).

Summit Racing has several Auto Meter black or white face 0-30 ohm gauges in 2-1/16" dia and 2-5/8" diameter.
I don't remember offhand which diameter our gauges are, but one of these will fit and will work with a 12V system.