Fuel gauge difficulties

[chrysler1941]

21 minutes ago, Dunkin said:

Thanks for sending this, it's very informative.  Me and my friends were not 100% sure how these worked, so this helps.  We are impressed with whomever came up with this over 70 years ago.  I am not well versed with electrical components, so forgive me if this is a dumb question...in looking at the shop manual regarding this gauge, is testing/calibrating based on the truck being positive ground?  

You are welcome. There are no dumb questions. Electrics is not easy. 

I cannot answer about your truck, I'll have to see your electric schematic. Usually they will show battery ground.

Theoretically these type gauges are not polarity sensitive, they will just show opposite.  They will also work with 12 volts, but bimetal blades will heat up to fast and may not last.

[Dunkin]

Hey Chrysler1941,

 

Would you be able to tell me if my gauge should read empty when sitting in the palm of my hand with no wires connected to it?  I've been messing with this gauge for months and I thought it always read empty, but noticed recently that it reads over 3/4's full.  I might just be losing my mind since I've been looking at this thing way too long?

[chrysler1941]

30 minutes ago, Dunkin said:

Hey Chrysler1941,

 

Would you be able to tell me if my gauge should read empty when sitting in the palm of my hand with no wires connected to it?  I've been messing with this gauge for months and I thought it always read empty, but noticed recently that it reads over 3/4's full.  I might just be losing my mind since I've been looking at this thing way too long?

Looking at your photo. it seems the pointer is twisted. Hard to tell. Unless the needle is bent,  it should be point at 12 o'clock. It only moves when current flows.

If you look at PDF, there are calibrating arms. These will move needle. Seen many move the needle to empty. But it will give a false reading.

Edited April 11, 2021 by chrysler1941

[Dunkin]

On 4/11/2021 at 10:27 AM, chrysler1941 said:

Looking at your photo. it seems the pointer is twisted. Hard to tell. Unless the needle is bent,  it should be point at 12 o'clock. It only moves when current flows.

If you look at PDF, there are calibrating arms. These will move needle. Seen many move the needle to empty. But it will give a false reading.

The shop manual you sent along with other information got me going down the right path since I am now at least getting a reading.  I know that when I took it apart to send in to clean and calibrate all 3 posts were used, so when told to only use 2 I scratched my head.  It now reads 1/2 full which I believe is about right.  I am going to fill her up this weekend and see what it does.  The only concern is that when I shut the truck off, the gauge moves up a bit above 1/2 full.  If I reverse the 2 wires from the sending unit and shut the truck off, then the unit reads super full.  I would assume that it should read empty when off with correct hook up.  Making progress, although not 100% confident that I have it figured out quite yet.

[Dunkin]

So I took the Dodge to the gas station to fill her up.  Took 14 gallons and when I started her up it read "Full"....yes!!  Then as I pulled out of the gas station I looked down and it read just past 1/2 full.  WTH?  The 3rd photo is with the truck off.  Any ideas where to go from here?

[1949 Wraith]

With the power off needle should point below E. Your previous photo showed pointer at 2/3 full when out of the truck. Are the springs attached at the back of the gauge?

[chrysler1941]

15 hours ago, Dunkin said:

So I took the Dodge to the gas station to fill her up.  Took 14 gallons and when I started her up it read "Full"....yes!!  Then as I pulled out of the gas station I looked down and it read just past 1/2 full.  WTH?  The 3rd photo is with the truck off.  Any ideas where to go from here?

Difficult to say not knowing what has been done. Running 12 v? Loose connection? Faulty sender ?

[Dunkin]

 

8 hours ago, 1949 Wraith said:

With the power off needle should point below E. Your previous photo showed pointer at 2/3 full when out of the truck. Are the springs attached at the back of the gauge?

I only remember the spring on the bottom of the gauge, so I will need take it apart again to check.  At one point the gauge did read E, so I must have done something while tinkering with it.

Edited April 19, 2021 by Dunkin

[Veemoney]

My 47WC fuel gauge has not worked since I had it so I'm checking it out. This and some other posts have helped a lot. Especially those pages attached from the manual explaining the thermostatic fuel gauge system which is what I have. 

 

Not sure if anyone found the correct replacement sender for the thermostatic gauge or a work-a-round for a newer sending unit. I pulled my sender apart and cleaned it up and adjusted the wiper so it is working with the gauge on the shop bench. Working now despite the resistor being warped and having a few windings broke. I posted a few pictures of my sender insides for anyone curious on the insides. Any new info on replacement senders for the thermostatic fuel gauge system or possibly the winding portion?

?

Thanks.

[MBF]

You need a Runtz type resistor that doesn’t require a lot of amps to function.  If you’ve converted to 12v + ground you’re probably going to need to reverse the wires on the gauge to make it work properly

[Dunkin]

On 8/8/2022 at 7:14 PM, MBF said:

You need a Runtz type resistor that doesn’t require a lot of amps to function.  If you’ve converted to 12v + ground you’re probably going to need to reverse the wires on the gauge to make it work properly

Now that the weather is set to cool some in the inferno I live in, I will get back to this project.  Interesting that before sending off my gauges to be rebuilt there was no resistor installed and the fuel gauge worked properly.