temp sending unit

[Brian Mauro]

I'm trying to figure out if my sending unit for the temp gauge or the gauge itself is bad, so I took the liberty of posting some pics. The first picture is straight out of the box with the Ohm meter, and the second one is at operating temp with a thermometer. The gauge goes to the HOT when it is running and does not stay in the "operating range" on the gauge, I had the cluster and gauges replaced or calibrated any advice would be great.

 

[Dana67Dart]

Photos are not coming through.

 

[Dana67Dart]

If your gauge reads high or pegged that suggests a short or near short in the sending unit wire

You say you had your gauges changed or calibrated... The aftermarket gauges might need a sender that is designed for them.

I recall seeing this on the classic website regarding their replacement gauges.

If you disconnect the sender wire at the sender and the guard still reads high that is a dead giveaway that there is a short or close to short in the wire.

For a stock sender the resistance at room temp should be above 75 ohms, maybe even in the hundreds of ohms.

At standard operating temp it should be around 23 ohms (about 1/2 scale on the gauge) and when boiling over around 10 ohms.

 

[Brian Mauro]

If your gauge reads high or pegged that suggests a short or near short in the sending unit wire

You say you had your gauges changed or calibrated... The aftermarket gauges might need a sender that is designed for them.

I recall seeing this on the classic website regarding their replacement gauges.

If you disconnect the sender wire at the sender and the guard still reads high that is a dead giveaway that there is a short or close to short in the wire.

For a stock sender the resistance at room temp should be above 75 ohms, maybe even in the hundreds of ohms.

At standard operating temp it should be around 23 ohms (about 1/2 scale on the gauge) and when boiling over around 10 ohms.

Yes, I had the cluster completely done over when the sender wire is pulled it goes too cold like with the key off, when it is at operating temp 180 degrees it is almost pegged to hot I have bought 3 senders from various vendors and removed the cluster from the dash to change out the gauge with a none NOS one still no change so I broke down and bought a NOS sender, the saga continues.....

 

[Brian Mauro]

Yes, I had the cluster completely done over when the sender wire is pulled it goes too cold like with the key off, when it is at operating temp 180 degrees it is almost pegged to hot I have bought 3 senders from various vendors and removed the cluster from the dash to change out the gauge with a none NOS one still no change so I broke down and bought a NOS sender, the saga continues.....

 

[Brian Mauro]

Photos are not coming through.

 

[Dana67Dart]

153 ohms cold is normal.
29 ohms @180 deg is a little high but not as high as you gauge photo shows.23 should be about straight up needle.

The gauges have 2 adjustments on them one sets the high scale at about 10 ohms, the other sets the low scale at about 73 ohms.

A combination of the two adjusts the mid scale. It's a balancing act to get it right.

Perhaps the repair facility did not get it right.

My 67 reads just over the low of the normal except for real hot days