Temp Guage not working.

[jauch]

I'm struggling with getting my water temp gauge working. Here's what ive done so far, pulled off the sending unit wire and grounded it and the gauge pings out just fine as it should so the gauge and wire are good at that point, you'd assume just a bad sensor, so i picked up a new one and installed it without any tape to ensure it gets a good ground from the intake, when i took out old sensor, coolant pored out so good water flow there, but still not a sign of life from the gauge.. any other suggestions would be helpful.

thanks,

tim

[Bullitt-]

You can use an Ohmmeter to check the sending unit for changes in resistance at different temperatures. I've seen some numbers posted here, I'll see if a search turns anything up. 

[Bullitt-]

http://www.cuda-challenger.com/cc/index.php?topic=39320.msg394751#msg394751

I measured the new one I got from pepboys and it came out pretty close as the Napa.

Napa

cold 71* 255 ohms                 warm 180*    33 ohms

Pepboys

cold 71* 200 ohms                 warm 180*     31 ohms

[dodj]

Engine grounds in place?

[72rtchallenger]

Engine grounds in place?

  check an make sure you have a good ground to the engine

[jauch]

Engine ground is good, i tested the gauge and line by grounding it to the block and it ping'd the gauge out just fine

[ShelbyDogg]

My cooling system is so efficient that my temp gauge barely reads with a 195 degree thermostat. Are you sure that it isn't reading right? Do you have a thermostat in your waterneck?

[jauch]

My cooling system is so efficient that my temp gauge barely reads with a 195 degree thermostat. Are you sure that it isn't reading right? Do you have a thermostat in your waterneck?

i have a 185 thermo in the waterneck, the gauge doesn't move at all, i'll get an ohm meter and check the sensor both on cold start and running for awhile

[ShelbyDogg]

A 10 ohm resistor shoud stop your guage on the full or top line.  Try your sender in a pot of boiling water on the stove to see what kind of resistance comes out of it. Use a candy thermometer to check the temp.

[jauch]

I'm still at a loss, ive picked up 3 temp sensors from different manufactures and they all are fairly close to the same ohm readings between 255 on the cold side to 35 on the hot. I can get the gauge to finally move up toward the hot side once i put the wire on the sensor and ground it off while putting a lighter to the sensor to heat it up long enough. what do you think about the thermostat issue?

[Bullitt-]

I would think that you have proved the hardware is good, only two things come to mind.
1- there is not enough coolant in the system to effect the sending unit.
2- the ground to the intake is poor where the sending unit installs.

[jauch]

I would think that you have proved the hardware is good, only two things come to mind.
1- there is not enough coolant in the system to effect the sending unit.
2- the ground to the intake is poor where the sending unit installs.

Just tested the gauge to see where the needle falls: at cold the ohms are at 55+, and middle gauge ohms at around 25, and at Hot on gauge ohms at 12-13 ohms. I checked to ohms setting on the sensor with the meter ground on the base of the sensor then with the ground on the battery ground and the ohm change between them is about a 2 to 3 ohm difference, so i think the ground is within a good tolerance.

[jauch]

I've notice just a bit ago after a 20 min drive that the gauge will move up but stays just a tick above the cold mark on the gauge, but when i turn the car off then turn the key on, the gauge will move up to about 1/4 the way up, so its looking like it just doesn't get hot enough to dump the sensors ohms down enough to show up on the gauge. maybe i'll look into the 195 thermostat to see what change it'll make... maybe the cooling is just efficient in this car.

[willard]

I have a bone stock 383 with AC and 26 mopar radiator. Gauge reads a hair above the bottom line (LOW) when engine reaches operating temperature, a little bit more, maybe 0,05" when I run on the freeway at 4000 rpm. However when I blew heater hose 2 days ago the needle went up very quickly as I lost the cooling fluid, up to 3/4 scale at a 1/2 mile distance.
The point is - even if you're low on coolant, the gauge should read at least at the bottom line (LOW).
If the gauge jumps after you shut down the engine - there's a electrical gremlin somehwere...

[UKcuda]

If the gauge jumps after you shut down the engine - there's a electrical gremlin somehwere...

It's normal for the temp. to increase for a short time after you shut off.  All the cold air rushing into the engine has a cooling effect on the inlet manifold etc. so it is cooler than the other parts when the engine is running.  After you shut off it all evens out and the inlet manifold temp. increases before it all finally cools down.

It's common for the senders to make the gauge read low.

If you want the gauge to read higher you can put a shunt resistor in parallel with the sender.  It looks like you need something about 80-100 ohms.  You can go here to work it out the easy way:

http://www.sengpielaudio.com/calculator-paralresist.htm