Reversed gas gauge in a 00 neon

Mr. Pink · Post by **Mr. Pink** » Sat Jul 24, 2010 6:09 am

Well i have been dealing with this since day 1 on the car, the Previous owner said its two plugs that need to be switched around. but i want a second opinion. My problem is exactly what the title of this thread states, F=E and E=F. It pissed me off the first day i drove the car since i forgot about the gas gauge and ended up running out of gas. The owner before last had the fuel pump replaced but i guess they plugged something in wrong. I dont have a lift to get at the plugs and i dont know if i will be able to just reach my hand up there and unplug them so does anyone have a suggestion sans dropping the tank, I really dont want to deal with that.

Post by **occasional demons** » Sat Jul 24, 2010 9:31 am

I don't think the connector can be plugged in backwards. The connector is a 4 pin; it also feeds the FP Pins 1 (+) (DG/WT) and 4 (-) (BK) I doubt anything would work if it was reversed.

Possibly the sender it self was wired wrong, or someone cut the wires, and reversed them at the connector. That is the only place the ground (Black/light green tracer) and the wire to the cluster (Dark Blue) are together. But I would think if the DB wire was spliced to the ground, it would read full all the time.

If the wiring hasn't been tampered with, I'll bet the sender resistor is backwards. Not sure if it could be turned around tho. You have a single wire (DB, pin 3) going from the cluster to the sender.Then from the sender to ground. (BK/LG, pin 2)

You should be able to reach it from the front of the tank. IIRC, the whole module can be snaked out without dropping the tank.

fixitmattman · Post by **fixitmattman** » Sat Jul 24, 2010 11:30 am

Reversing the wiring won't do anything since it's based on resistance, won't matter how you hook it up. They probably installed the sender upside down (if that's possible) or installed the wrong sender.

Post by **occasional demons** » Sat Jul 24, 2010 11:43 am

True.

Looking again at the diagram it would only be like wiring a bulb backwards. The resistance will still be the same.

Mr. Pink · Post by **Mr. Pink** » Sat Jul 24, 2010 5:36 pm

i wonder if it could be the cluster itself

Post by **occasional demons** » Sat Jul 24, 2010 7:47 pm

You could test it by buying a 100 ohm resistor at Radio shack, and putting it from the DB wire to ground. You can do this under the dash, by using a splice connector for the easiest, and prolly less worry about corrosion damage. The gauge should read just above empty. You can leave it connected to the tank, as it will bypass that part of the circuit.

NickKo · Post by **NickKo** » Sat Jul 24, 2010 11:24 pm

If this were my own car, I'd try reversing the polarity/wiring at the plug, "just in case" it does fix it.

If this doesn't work, get ready to drop the tank.

- Nick

Post by **occasional demons** » Sun Jul 25, 2010 1:56 am

The only thing that would cause this, other than the sender somehow being upside down, would be if the wrong end of the variable resistor was grounded. Which would be internal to the sender.

As wired correctly

wires reversed

As you can see the resistance would not change, either way. It would still go across the same length of windings, so the gauge would read the same. You would need to change the complete wiring system polarity to affect this. Everything would be backwards.

Sender wired wrong

This is about what's left as the most probable cause. The internal wiring to the wound resistor is on the wrong end.

jbwunderlich · Post by **jbwunderlich** » Sun Jul 25, 2010 5:12 pm

i ran into this exact problem when i installed a 2nd gen fuel pump module in a 1st gen maybe you have a 1st gen pump and or sending unit in your car

NickKo · Post by **NickKo** » Mon Jul 26, 2010 12:40 am

jbwunderlich wrote:i ran into this exact problem when i installed a 2nd gen fuel pump module in a 1st gen maybe you have a 1st gen pump and or sending unit in your car

This is what I was wondering, too....

- Nick

Mr. Pink · Post by **Mr. Pink** » Mon Jul 26, 2010 7:47 am

I'll fix it eventually. the car is sidelined(piston slap) as i work on my 99 that i picked up yesterday.