Im buying all new isspro gauges for my 86 F250. I have two choices for my fuel level gauge, one is 0 ohms empty 90 full. the other 240 ohms empty 33 full. Which one will work correctly with my factory fuel gauge wiring? the website dosnt clarify and i dont want to order the wrong gauge. thanks

 

Look up stock sending units on rockauto.com, I believe some of the listings explain the ohm measurements as I totally forgot.

Stuff changed in I believe 1987; installing the wrong one will only result in the gauge reading opposite of what it really is.

 

10 ohms full and 72 empty.

 

10 to 75

10 characters

 

So the 240 full 10 empty is my best bet? Thanks for the input

 

You will probably show empty at some place above half a tank. If you think that is acceptable then go for it. But I wouldn't think so were it me.

 

I'm facing the same dilemma. Bought a SunPro fuel gauge ($17, 240-33 ohms) and learned when it came that the instructions call for a SunPro sender to be installed thru a new hole in the tank. I don't see any way to make that gauge work well with the Ford sender (73-10 ohms).

Had the online listing for the SunPro gauge told me I needed to install an additional sender in the tank, it wouldn't have been a big deal to put one in before the Mustang tank was installed behind the rear axle. Now, I'm not eager to deal with the fuel in the tank, remove the tank, cut a hole and install the Sunpro sender. But unless I do, it looks like I'll have a nearly useless fuel gauge.

 

Damn I was afraid of that...hmmm I wonder if I could use the sunpro sender with my isspro gauge? It wouldn't be that big of a deal for me to put a sender in my tank, I need to drop it anyway lol

 

According to SunPro tech, its sender has 240 ohms empty, 130 ohms at half full, and 33 ohms full. If that's what your gauge needs it should work just fine.

Here's some info I copied from fordification.com.

Ohms/Resistance
(Empty/Full)

Popular Models

0-90 Ohms most GM cars, 1965-up
73-10 Ohms pre-1989 Fords & most Chryslers
240-33.5 Ohms Industry standard, works on many popular cars
0-30 Ohms most pre-1965 GM cars
16-158 Ohms most '89-up Fords

I'm trying to find the ohm rating for a 2" Ford tractor gauge to see if it would work with my pre-1989 Mustang sender. Its a pretty good match for the other SunPro gauges, just has a black needle rather than orange.

 

An ohm is a unit of electrical resistance... http://en.wikipedia.org/wiki/Ohm
The amount if resistance (not) added to a circuit increases and decreases as the float on the sending unit moves up and down.... how the dash gauge reacts to this depends on its range of operation.

For example, we can say:

- A low amount of resistance in the circuit = high amount of power being delivered to the gauge = it swings fully in one direction

- A high amount of resistance in the circuit = lower amount of power being delivered to the gauge = the same gauge being closer to the other end of the operating spectrum.

One will most likely scour the Internet forever searching for an "ohm rating" for any particular gauge as no such rating actually exists... because, again - the number of ohms applied to a circuit is dictated by the sending unit, and the gauge merely reacts to the amount of voltage being passed through the sending unit to it.

 

It sounds like I need the 10/75, so I guess the sunpro sender won't work either...the only thing I can think of is if the gauge I buy can be calibrated or adjusted to my truck. If that makes sense

 

Yes, you need the 10/75 if you use the stock gauge.

 

If you could take the original sending unit out and re-configure the resistance box so it read backwards, I believe it would work for you. Then make sure the arm in the resistance box came all the way to the end to give you zero ohms at empty. The other end of the box should give you at least 73 ohms, but in my experience these numbers are just a guideline, and you may indeed get close to 90 ohms out of it.

The you could buy the 0-90 ohm guage.

In the real world there is not a person on this board who will tell you the original Ford fuel guage is anywhere near accurate. Each truck is different, with it's own quirks. My 89 rear tank is pretty smooth throughout the time the fuel is used. My front tank will sit past full for most of the tank, and then with about half the tank left it will start falling rapidly. But you learn to compensate for it, I believe the most critical part of the whole thing is the empty area. If the tank is getting near empty, I want the guage to tell me this.

I have had several older GM cars with the 0 empty 90 full and the 0 empty 30 full setups. The most critical part for these guages is the ground. You need that zero ohms. When the arm on the resistance box comes around and is pretty much a dead short to ground(that's how it works) you want that ground to be good. I have been stranded several times by my old GM cars because the ground was corroded, and instead of getting near zero ohms, the corrosion "added" about 10 or so ohms, and the guage never would fall all the way down to "empty".

You can take these sending units apart if you like fiddling with stuff like that.

 

Good info thanks. I think ill do that, ill buy the 0/90 gauge and modify my sendin unit to make it work. It Dosnt need to be perfect just tell me when it's empty lol I'm planning on putting a bronco fuel tank in the truck anyway so ill do it when the tank is out