M38A1 Fuel gauge

[JEB]

Hi

The fuel gauge in my A1 always seems to read low.
During restoration, it received a new sending unit, I can't recall if the gauge (a SW- 505C) is NOS or used.

Despite it being full (looking down the wide mouth it is at the base of the filler tube), it still reads about a half tank (with vehicle running in garage, I know with my other cars, they tend to read more when in actual use...due to pressure?).

When using fuel, the gauge acts normally...it goes down.

So...
-Are these gauges every very accurate?
-Can one adjust the sending unit?

 

[NDT]

My guess is that the china made sender does not have the proper resistance values. On mine, I ran a backup ground wire to the sender since the tank is somewhat insulated sitting on those cushion straps.

 

[JEB]

When restoring n the Jeep, I was given a correct gauge, but it was not compatible with the sender, different ohms.
Now this gauge is having issues. It was used and donated by a friend.

So, what next..another gauge, or different sender?


Also: One dealer has a NOS gauge but they want $250 for it. Seems like a lot when a repro unit is about $65.

 

[NDT]

I always thought all MS fuel gauges had the same electrical values regardless of era. Before you buy stuff, double check the grounding of both the gauge and sender.

 

[DeetFreek]

Ok, my dumb thought is going to be this, is the float arm out of whack or hanging up?

 

[JEB]

The guy who put it in swears it is not.
But, I'll ask him to check it because:
A. The units are talking to each other, so it's not totally out of whack...(makes sense to me,.how.about those of you who know more than me on this matter?).
2. Check the obvious before buying more parts.