[AT] How to test a fuel gauge/Sender??

[Mike Sloane]

Most fuel gauge senders are just variable resistors - a coil of wire 
with a sliding contact. If you attach one probe from your ohmmeter to 
the ground and one to the insulated terminal, you should see the 
resistance change as you move the float up and down. It isn't important 
how much resistance is there, as long as the readings go up and down 
(usually from 0 to anywhere from 30 to 200 ohms, depending on particular 
sender/meter combo). The fuel gauge is essentially a volt meter set up 
in series with the sender, reading the reduced voltage coming from the 
sender. DO NOT put full battery voltage across the fuel gauge meter's 
terminals - you will probably burn it out (if it hasn't already). If you 
have an old weak AA battery or, better yet, access to a variable DC 
power supply, try that to see if you can get any meter movement.

I have not had any luck repairing IH senders that fell apart over time, 
nor are the gauges easily repairable. On the Int. 240U, I went cheap and 
bought a matched inexpensive sender/gauge set from JC Whitney, It works 
fine, but, of course, it isn't "original. On the 706, the gauge was 
fine, and I was able to get a used sender from Biewer's. My next project 
is the one on the Farmall 340...

Mike

John Wilkens wrote:

> My Massey 175 fuel gauge is not working.  Can any of you electronic 
> wizards suggest how I might determine whether the gauge or sender unit 
> is bad (without buying both new parts for a try)?  I have an ohm meter 
> but don't know what to do with it with what I guess are resistances 
> involved.    I'd like to fix the bad unit while I have the tank out.     
> John
> 
>                    In the wide-open spaces of NE Oregon
>  
> 
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-- 
Mike Sloane
Allamuchy NJ
Email: (msloane at att.net)
Website: <http://www.geocities.com/mikesloane>
Blog: <www.mikesloane.blogspot.com
Tractor images: <www.fotki.com/mikesloane>
Work: none - retired

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