How do I fix my gas gauge? I checked the wire at the tank and it seems OK. I pulled the float also. Any way to test the float? I manually lifted the float while connected (out of the tank) and put the key in "run" position but the needle doesn't move. It seems like nothing is broken. I traced the wire into the trunk and it's in good shape. I don't think it's a fuse 'cause my temp and alternator gauges are working. This car has been sitting for 10+ years. Help!

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"Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of Him to whom we must give account."

First you need to know how the sending Unit works..

There is a coil in it, which will only allow so much volts threw. The Fuller the tank less of the coil the volts goes threw, as the gas in the tank goes down more of the coil it has to pass threw lowering the voltage. so basicly you gauge is just reading the ammount of volts its getting.

Normally what goes wrong is the sending unit.
Try this:
Disconnect the wire on the sending unit, then ground it good place on the car. it should be reading a full tank, if it is something in your sending unit is bad, if its still not reading, change your ground a few times and try again.

After that if its still not reading you need to test the gauge by doing fallowing:
Remove the dash to get access to the gauge, next you need to hook up 2 C or D batterys in series, this will have an out put of 3volts. Your gas gauge works off of 5 volt system(5volts = Full, 0volts = Empty). you need to connect the batterys to the terminals on the gas gauge. You may need to switch them arround. This should result in a little more than 1/2 tank in reading, if it doesn't your gauge is bad.

If you got a reading the 1st or 2nd time, you need to check the sending unit by doing:

Method one(don't have to pull the unit) take a Ohm tester and connect one lead to the sending unit wire connection, and the other to good ground(upper fuel line) You will likely get no reading meaning something is bad... next step... if you do get a reading you have a wiring problem some place.

Method two(pull it!) get a screw drive and a hammer. there is ring that hold the unit in place it has 4 tags that stick up... you need put your screw driver on it so it will rotate counter clockwise, and tap it with the hammer, if it hasn't been messed with in sometime a lot of force maybe required....
when you get it out, you need to check things to see if the float doesn't have a hole, and the coil isn't busted...

a few notes...
if you remove the sending unit a new seal is a must, you might also want to get a new sock filter if its been a long time....
if none of this helps it is likely a wiring problem....
also there is meant to be a "grounding strap" that connects the fuel line on the sending unit to main line... this may or may not effect you having no reading... I would say rarely will it make it not work... but could... I have 2 cars with no straps and they both work fine.....

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Mike C
http://cuda.iclownz.com
67 - Barracuda Coupe - 225 - Automatic

Thanks for the info. I think you covered all the bases. Where can I get the gasket/sock filter? Any auto parts store?

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"Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of Him to whom we must give account."

I dont think you can get them at a parts store.... but any local mopar source should be able to get them for you.... or called Kollar Dodge and order from them....

they are pretty ez to come by sense they fit most mopar's...

http://www.kollerparts.com

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Mike C
http://cuda.iclownz.com
67 - Barracuda Coupe - 225 - Automatic

3 more things...

- Make sure that tank isnt very full if you pull it (I know sounds dumb but I know a guy that got sick from gas cuz he didnt think about it....)

- You can get a replacment sending unit for like $90 sometimes less... ( my mopar parts dealer said they dont have them anymore but its BS... just look for A-Body sending unit... they work for 63-76 I think...)

- make sure before you declare anything dead... you double and triple check your work.....

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Mike C
http://cuda.iclownz.com
67 - Barracuda Coupe - 225 - Automatic

Thanks for the advice. My gauge is working now. Not sure what it was. I took out the tank and tested the sending unit. It worked so I cleaned the grounding strap and fuel line. I got the seal (part # 3404451) and sock filter (part# 1670694) at the dealership for anyone who is interested.

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"Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of Him to whom we must give account."

hehe then you had better luck with my 67... my sending unit was busted in everyway you can think of....

Float had a hole, float rod was bent arround the fuel line(I dont know how in the hell this happened?) coil was busted.. and the sodering arround the fuel line busted so it leaked... *sigh*

however I was able to fix it with only one slight problem 1/8th of a tank really Empty... hehe someday I will buy a new sending unit....

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Mike C
http://cuda.iclownz.com
67 - Barracuda Coupe - 225 - Automatic

Just a minor detail, the gauge reads current, not voltage.

Simple test:

Ground the lead at the tank. If gauge goes to full, gauge and regulator are OK. If not, check ground strap. If ground strap is OK then sender is bad. Check with an ohmmeter. If it doesn't read anything (open circuit) then it is toast.

If grounding the lead at the tank does not max the gauge then you should try to ground the appropriate lead behind the dash to verify that the lead from the dash to the tank is OK. I have never seen one go bad but it could.

If both the gas gauge and temp gauge don't work, then the regulator is bad. These were internal to the gas gauge pre '67 and after that there is a replacable regulator that plugs into the back of the dash. See my article on instrument regulators at http://slantsix.org/articles/instrument ... nt_reg.htm

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Chuck Rivers, Webmaster

Well your correct about it being current and no voltage, I wrote the reply very late and was very tired, thus the mistake...

everyone talks about the ground strap, it needs to be checked but I dont think its the problem a lot of people do...

about your article, sense I dont know all that much about early A-Body clusters concerning the placment of the voltage regulator.... is it possible to remove or bypass the old regulator inside the gas gauge and use your method?

also if you want to switch your bi-metal voltage regulator with something better...
http://jefframin.org/library/IVR.1.jpg
http://jefframin.org/library/IVR.2.jpg

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Mike C
http://cuda.iclownz.com
67 - Barracuda Coupe - 225 - Automatic

The ground strap was a major problem on my Dart 'cause it was missing! I used alligator clips connected with a wire and it has been that way since '78!

As far as using my method, you can open up the gauge by drilling out the rivets and then just cut loose the wires to the regulator. I designed a solid state replacement years ago but did not post that info because I figured it would be easier to use a later regulator. With the cost of the regulators so high, I should re-think that. I used the same Radio Shack regulator. Installing in the old A-Body gauge is a bit of trouble because the regulator needs to have a heat sink, so it would have to be screwed to the gauge case somewhere.

BTW, I don't think that the reason is "lost in the annals of engineering history". The reason for the regulator is so that the gauge readings will not fluctuate with the battery charge.

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Chuck Rivers, Webmaster

Well there is a lot of things done on older cars that look dumb by today standards... such as points, and voltage regulator's... but if oyu look at what they had to work with, they did very impressive things I would have never thought of...

Mopar on!

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Mike C
http://cuda.iclownz.com
67 - Barracuda Coupe - 225 - Automatic

Yea, creative engineering. I recently fixed a '66 Valiant that someone had upgraded to the later '73 voltage regulator. The regulator was mounted on the inner fender and then poorly wired into the system. I returned it to stock and got the $10 electronic replacement from a NAPA dealer. The guy spent more time than $10 worth making the jury-rigged mod!

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Chuck Rivers, Webmaster

Chuck, minor point. The instrument voltage regulator on my 65 Valiant is separate from the fuel gauge. Don't remember which cars had separate regulators, and which were in the fuel gauge

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Interesting. My dad's '65 Dart has it in the gauge, so I thought the Valiant was the same. Thanks for the info. Is the regulator like the one on a '67 Dart?

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Chuck Rivers, Webmaster

Chuck, I will have to check my old wiring diagrams, but if I remember correctly there were differences in the dash wiring between Valiant, Dart, and Barracuda, in the mid sixties.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225