Broken Fuel Gage
 

Hello all. I have a question on how the fuel gage works in a 65 Mustang. I just got mine on the road and the fuel gage has never worked. I recently replaced the instrument cluster to check the gage itself and that is not the problem. I also replaced the float and sending unit in the tank with a brand new one, and still no luck. From what I can tell - there is one wire running from the sending unit to the gage. There is another connecter on the back of the guage also with a wire also attached. Thinking that the wire from the sending unit was broken or split - I ran a new wire from the sending unit to the gage and it still did not fix the problem. I have to think that the other wire to the fuel gage is suposed to power this thing and it is broken, so I did an experiment. I added a small charge to the one wire going to the sending unit and the guage fired right up. The problem I have is that I just added a charge to the sending unit that sits in 10 gallons of gas and the thought of doing this scared me so I immediatly disconnected it. Does anyone know the proper way this gage is supposed to work and be wired? Thanks for any advise.

I'm troubleshooting the gauges on my car right now (If I ever get a chance to work on the car):rolleyes: .
First off do you have the stock idiot gauge cluster or the GT option?
Assuming that you have the GT option (I dont know exactly how differently the stock '65 piece was wired) Does your car have an IVR <instrument voltage regulator>on the back of the cluster? (On my 66 it is a 2 prong silver box about 1/2 the size of a zippo). This keeps the gauge from getting a full 12 volt charge, which will fry the gauge. Mine was already bypassed when I bought the car.

I would first make sure that the fuel gauge is hooked to the IVR, on my car the wire is green/black. The wiring should run from the loom to the IVR, from that out to the fuel/temp/oil gauges. Then each unit will have a color coded wire running to the sender.

If the gauge responded to a small charge it may just be the wiring in the loom, especially if the sender has been replaced already. If you want, PM me, and I'll forward what one of the other guys here sent me so far.

J

What I did?
 

What I did was to remove the sending unit from the tank. Put a voltage meter on the output lead and check to see that different voltages occur at different float levels (extreme high/low).

If that occurs, reconnect everything and recheck at the incoming lead to the ivr. (sending unit still out of tank). If you get different readings there, then reconnect to the gauge. The gauge should register a different reading when the sending unit float is at different points, still out of tank.

I did end up having to bend and alter the sending unit float position to get the readings I wanted (above full when full and below empty when truly empty).

Rev

guage problems also....
 

I too have that same exact problem and I have tried the exact same things....(running new wire) I could have sworn that I saw the thing working a few times....I have replaced the sender in the tank. as well I replace the ivr. Im waiting for other suggestions to check. I am not wiring guru......Ill keep watching and trying..

Brian

I think I have it
 

I do believe that my problem is that there is no power to the guage. If memory serves me - there are 2 terminals on the back of the gage - one for the sending unit in the tank and the other one from the IVR. I know the gage works because when I put power to the wire running to the sending unit - it fires right up. I am going to bet once I get the dash apart and check if there is power to the other terminal - I am going to find that it is dead...Just another 2 weeks and the car goes into winter storage for more resto work, so as soon as I know if this will fix the problem - I will let you know.

I am going to try to attach a picture of the back of a 66 instrument panel. I think it is the same as the 65 GT instrument panel. It appears to me that the second wire you are looking for should be coming off of the Oil Pressure gauge. (lower left side of diagram). Hopefully this might help you out.

Thanks for the picture
 

I think that helps a lot. It appears that the one wire is directly from the fuel Gauge (finally got the spelling right :) and the other comes from oil unit which is run from the IVR so I am going to assume that that is the power supply that I have been thinking is not working. I guess a simple test of power to that terminal will tell all. Thanks again for the pic. I should know in a week or so. I will be an expert on the Fuel Gauge by then...now on to the steering box and front disk brakes (new post)

TJ

It was the IVR
 

Ok - I pulled the entire insutrument cluster and did some tests....It was the IVR...I removed it and it was rattling (really Broken) so I replaced it and all is working with the Fuel Guage now....

Thanks for all the suggestions. Just a shame the darn thing cost so much!

TJ

Re: It was the IVR
 

I thought they were like $10-12?

Rev

I paid $27 for mine:mad:
Glad that was the culprit tho.:D

J

The local Mustang Supplier
 

My mustang supplier wants $40.00 for the thing. I think I am going to try a national auto parts store this weekend and see if they have it cheaper...Either way - I will be glad to get the dash back together and have the fuel guage working.

Repro
 

I'm looking at the John's Mustang 2003 catalogue right now. It says 24.95 for a repro 1965-66 instument voltage regulator.

Rev

Re: Repro
 

As well as I am looking at the Paddock's Mustang Parts and Accessories Catalog and their price for the IVR is $22.95. But, I have found that you can find most of the parts you need at Auto Zone and places like that for a little less expensive.

Regulator fixed the problem
 

I received the Regulator in the mail last night and installed on the back of the instrument cluster....Now the Fuel Gauge works like a charm. Thanks to everyone for all the help. Wish I would have known this from the start.
TJ

That's what everyone here enjoys doing. This place is awesome for problems that just won't go away. Chances are someone here has had the problem or seen it before.


THANK GOD FOR MUSTANG WORKS!!!