Mustang sending unit , Sunpro gauge . . . . help !

[=mike=]

Okay for those of you who don't know , I have a 64 Mustang gas tank in my car , stock sending unit ( both brand new ) , and just hooked up a nice black face Sunpro gas gauge . I get a full reading no mater how much damn gas is in the tank . . . how do I adjust this to make it work . Does it have to do with ohms , can I tweek the float arm in the tank or something . . . help http://www.jalopyjournal.com/ubbthreads/images/graemlins/confused.gif

[=mike=]

back to the front page for round 2 . . .

[El Caballo]

At least you will be right after you fill up everytime...

It sounds like there is a piece of the puzzle missing part-wise. I have a Ford shop manual for Mustangs and I will see if I can scan the schematic for you. Maybe there is a resistor or something that is missing and that is letting all the signal through. I dunno, 'lectristy is a black art to me. Could be your new sending unit is a POS, too.

[=mike=]

yeah this stuff is alchemy to me too. . . I'd appriciate any help at all http://www.jalopyjournal.com/ubbthreads/images/graemlins/smile.gif

[CharlieLed]

I can help you out mike. Do you plan to be in El Cajon anytime this weekend? I'll be here, I'm just up the hill from Dave's.

[=mike=]

Charlie , I am mostly going to be around the house / neighborhood this weekend . Building things in the backyard , any chance of some online tech I could use to trouble shoot my situation ?

[CharlieLed]

The basic circuit is made up of the gauge and the variable resistor on the float arm assembly. First you have to find out what kind of variable resistor is on the sending unit, some use reostats...that is, they were one-wire setups where one end of the variable resistor goes to ground and the other side is attached to the wiper arm. As the float goes up and down the wiper arm moves inside the variable sesitor whichs causes the resistance that is "sent" to the gauge to vary.
To get right to the point, if the resistor in the sending unit is too small or too large then it is outside the range of the gauge. If the gauge is looking for 0 ohms to be empty and 100 ohms to be full...and your sending unit varies from 500 to a 1000, then the gauge will always read full. In this example a resistor can be added in parallel which would bring the total resistance of the circuit back into range. Without having the car available to take voltage and resistance readings it's a little tough to tell what your specific condition is....

[CharlieLed]

Here's a page out of the overhaul manual for the stock Merc circuit...yours is different but the basic circuit is the same...

[=mike=]

okay , I see what you are saying . I don't know if I can make it out your way this weekend , but this seems like something you would be able to tackle for me . I will get in touch with you and maybe we can sort this out some how , I appriciate it !

[DrJ]

If this is the guage;
http://www.actron.com/cp7954.gif
Sunpro Ammeter - CP7954

* 60-0-60 Amp scale
* 60° scale
* Requires hook-up wire

This is the sending unit and resistance requirements;
Sunpro Fuel Level Sender - CP7583

* For use with fuel level gauges and 5" - 26" deep tanks.
* Includes gasket and mounting hardware.
* Resistance specifications:
* Empty: 240 ohms
* 1/4: 170 ohms
* 1/2: 120 ohms
* 3/4: 78 ohms
* Full: 28.6 ohms
*
I got that here; http://www.actron.com/cgi-bin/web_store.cgi?page=repgauge.htm&cart_id=9827995_10 789
or
http://www.actron.com/sunhome.htm
I got atricky-dicky light bar guage that was for a Chevy and at the time they made one compatible with Ford senders but I don't know if they still do.

[moondisc]

Sunpro uses their own sending unit. Different ohms than anything else. So you have to use their sending unit with their gauge.
Cheaper to get another brand of gauge with the correct ohms for a Ford.

[DrJ]

Check this out.
I think I will too! http://hp.autometer.com/products/traditional_chrome/electric_gauges/electric_gauges.html

[53choptop]

Moondisc and DrJ are right. I have the same set up and I had to buy a aftermarket fuel gauge, the sunpro i got did not work.

Ford sending units read from 10 ohms (full) to 73 ohms (emtpy). The guage I ended up getting got was an Autometer 2515 (like the one in the link above) in the "Traditional Chrome" series, got it cheap on ebay. When and if you are looking for another guage, make sure it is set up to read 10 full to 73 empty, these are Ford sending unit ohms.

Good luck

[=mike=]

damn you guys rule .. off to Auto Meter for me . That gauge looks the same as the one I have anyhow . . . banzai ! ! !


thanks a bunch .