Gauge wiring problem (electric water)

[281pony]

i know there is alot of good electrical advice in this forum. (jt, jricher, ect). so i wanted to post this here for some input.

this is my problem. since installing my electric water temp gauge, it has never registered right. it flys up rapidly once the car is running. takes about 30-45 seconds or so to go from 100-250 (max).

originally we thought sending unit. autometer sent me a new one. i installed it. the first time i ran the car after swapping, it read normal for about a minute. then it did the same thing again, and jumped up to 250 in about a minute.

there are single power wires run for the sending unit and lumination power. both ground wires are grounded to the same spot.

ive been told to try and ground the sending unit directly. so today, i put a ground wire on the stem of the sending unit in addition to the power wire. gauge pegged 250. i took it off, and it started from 100 and maxed out like usual.

my question, is there another way to ground the sending unit aside from what i did? any other issues that come to mind?

thanks for the help.

 

[HISSIN50]

As usual, I'm a little confused. The gauge should use resistance in the sending unit wire to register a reading on the guage. For instance, if you ground the wire that's on top of the sending unit, the gauge should peg at max.

The sending unit body does need to be well grounded (usually achieved via the motor and its threads) so your idea to ground the sender body was a good one. I have run dedicated ground wires from the sender housing to ground - just being sure that the wire gets no where neat where the actual sending unit wire wire attaches (or the gauge pegs).

For the issue, if all wiring looks good, and your sending unit wire ohms out with no resistance when disconnected (to make sure the wire didnt chafe and partially short during installation), I have one thought:

I recall from some time back, a guy said he got a gauge with a sending unit for another guage (as you know, they sell elec gauges with different scales) - basically the sending unit and gauge were not calibrated for eachother. He got the right sender and it was good-to-go. I know you got a second sending unit, but it's something to file away if all else fails.

I really dont have any great ideas though brah.

Good luck and bump.

 

[281pony]

my sending unit is mounted in the coolant crossover tube of my car, via an aluminum threaded insert. so it may not be grounding properly there.

ill post a pic, however. if i run a ground off the sending unit body, how would i attach such a wire/make a ground? that is what im confused on unless im completely missing it. the only real way to ground it i saw was to connect it the same way as the power.

the issue must lie in my grounding then, since it seems to have done the proper thing when i connected the ground wrong.

you remember me back with my fox, im not good with electrical. i know the rest of the wiring is good though, except this grounding thing seems to be the issue. if i can rule this out, ill know the gauge itself is bad.

edit: picturetrail is down, cant post pic for a bit of crossover tube mounted sender.

 

[HISSIN50]

ill post a pic, however. if i run a ground off the sending unit body, how would i attach such a wire/make a ground?

the issue must lie in my grounding then, since it seems to have done the proper thing when i connected the ground wrong.

I'm not sure that the ground on the sender will help. If you were reading way too cool, then I'd jump on that. But if the sender is capable of creating such a hot reading, that suggests it's grounded decently (you can ohm out the sender body if you want - it takes 10 seconds).

I have put a sender in a tee in rubber lines before (no ground at all) and soldering your own ground-wire to the sender body would work. If you want to do it for testing, bare the wire and zip tie it to the body or use an aligator clip. I am not conversant with the looks of your cooling system (a Degas set-up probably) so I really dont know about air pocket issues or the grounding issue - this is just my theoretical two cents.

I mainly just wanted to post about the grounding of the sender body probably not being a solution (it takes 2 mins to make a ground wire for testing though if you want to play with it). I'll have to let it simmer and see if something else comes to me.

Good luck!

 

[281pony]

damn, stangnet was down for me.

anyway, i was kinda down to it being a gauge issue also. nothing else seemed to make sense. im going to give autometer a call when they open today and see what they think.

i tried to ziptie the ground on like you suggested as well. same results. hopefully they will be as open to replacing my gauge as he was sending me a new sending unit.