Wiring on Back of Fuel Gauge

[mooney265]

I had all of my gauges out to have them re-faced and LED's put in them... Vintage Gauge did the work, and am very happy with them. I don't think I've got my Fuel Gauge wired correctly, though...

I have seen the wiring diagram, but am not too sure if I have the wires in the correct location on the Fuel Gauge...

Here's what I've got:
1. Green wire from sending unit to "G" on gauge
2. Brown Wire from sending unit to the Chassis
3. Black Wire from sending unit to Low Fuel Light??
4. Red/Black Wire going to "X" on Fuel Gauge

For some reason, the low fuel light doesn't come on anymore [Yes, the light bulb works when I jumper it]. My fuel gauge seems to be working properly. i say "seems" because when empty, the gauge still reads 1/4 full [maybe needle bent?]. When full, the gauge reads full.

When I removed it and bench-tested:

When empty: 68-Ohms [between Green and Brown]
When full: 3-Ohms [between Green and Brown]
When empty: Circuit from Green to Black is Complete [0-ohms]

Does anyone know where I've gone wrong? Thanks! Shannon

[Bob Kontak]

I looked at the 1978 electric diagram. What you have stated appears correct. However, I cannot confirm the red and black wire only because the diagram does not say "X"

I am just thinking out loud here - have never done this:

I would pull the gauge and keep it connected to the wires. Make the gauge go to the "empty" position and see if the light comes on on the dash. I am thinking it is a mechanical issue and the gauge cannot go to "E" when in the tank. Can it be positioned incorrectly?

Here is the 78 diagram:

See pdf page 6 and page 8

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_78SC_USA.pdf

[mooney265]

Bob, I have tried what you suggested and even took the sender apart... Like I told my wife - - "I wish I was an electrician..."

When the float is on the bottom, I'm getting 68-Ohms. At this point [68-ohms], the gauge reads 1/4 full and the light doesn't come on...

Thanks for the reply - - Shannon

Originally Posted by Bob Kontak

I looked at the 1978 electric diagram. What you have stated appears correct. However, I cannot confirm the red and black wire only because the diagram does not say "X"

I am just thinking out loud here - have never done this:

I would pull the gauge and keep it connected to the wires. Make the gauge go to the "empty" position and see if the light comes on on the dash. I am thinking it is a mechanical issue and the gauge cannot go to "E" when in the tank. Can it be positioned incorrectly?

Here is the 78 diagram:

See pdf page 6 and page 8

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_78SC_USA.pdf

[Bob Kontak]

Check this thread out. You can do some tank gauge cleaning. You can do some tank gauge resoldering and the late 1970's fuel gauges had some anomolies.

There - that covers everything. :-)

fuel guage needle is stuck???

[kerthunk]

I ran out to my '79 and snapped some pics for you.

[mooney265]

Looks like your Low Fuel Light has both the Red/Blk and Blk wires attached? If so, I've got something wrong...??

Originally Posted by kerthunk

I ran out to my '79 and snapped some pics for you.

[mooney265]

I've circled some items...
1. Is the Yellow Oval circling the Low Fuel Light Assembly?
2. Is the White Arrow pointing to the Solid Black Wire?
3. Is the Red Arrow pointing to the Red/Blk Power Wire?

And, are both the Black and Red/Blk Wires attached to the Low Fuel Light Assembly [circled in Yellow]? Somehow, I'm missing this assembly and just have a regular dash light assembly [with single wire] attached in the Low Fuel Light's slot...

Thanks, Shannon

[mooney265]

Here's the pic... sorry...

[Bob Kontak]

Red black feeds several terminals. It leap frogs from one connector to the other.

Thanks Kerthunk for the pic.

Shannon - as far as your last question I am pretty sure the answer is yes. I will let Kerthunk answer though as he has the part.

See diagram - bottom of page 6 in the link I sent you.

Shows what you are asking. Pics save a thousand words, though.

[kerthunk]

Originally Posted by mooney265

I've circled some items...
1. Is the Yellow Oval circling the Low Fuel Light Assembly?
2. Is the White Arrow pointing to the Solid Black Wire?
3. Is the Red Arrow pointing to the Red/Blk Power Wire?

And, are both the Black and Red/Blk Wires attached to the Low Fuel Light Assembly [circled in Yellow]? Somehow, I'm missing this assembly and just have a regular dash light assembly [with single wire] attached in the Low Fuel Light's slot...

Thanks, Shannon

1. Yes.
2. Yes.
3. Yes. The red/blk wire makes 3 hops on the gauge.

Yes, the black and red/blk wires are attached to the assembly. The assembly prevents the grounding of the lamp to the gauge. Since the red/blk is always hot and providing the +12v, the black controls wether the lamp is illuminated by it grounding as necessary. If the black is the only wire attached, then there will never be 12v hitting the lamp. Here is a close up pic:

[mooney265]

yes, from your diagram and kerthunk's pics, I can see I have the wrong light socket installed for the Low Fuel Light...

I'm going to have to get one [or, make one...]. I can see that what I need is a socket that has two leads on it. One for 12V and the other for the Black Lead from the Sender.

I'll get this fixed tomorrow! Thanks, Shannon

[kerthunk]

I think that this is the part you need (999.632.009.10):

Pelican Parts - Product Information: 999-632-009-10-OEM

There is also a listing for a "large bulb" holder (999.632.002.00).

You're welcome! GOOD LUCK!

[mooney265]

got it. Was able to temporarily use another one [from another gauge] to test and all seems to be working fine.

thanks again!