Classic/Antique Car Repair: temperature sending unit, oil pressure gauge, napa store

Question
I have a 1966 mustang. My temperature guage quit working. I replaced the water temp sending unit and it still doesn't work. I can take the wire off and touch it to the carburetor and the guage will max out, so I think the wiring and guage would be ok. But it won't max out on the engine. Could the engine not be grounded properly?

Answer
It is possible that there is a grounding problem causing this, but I doubt it, because you'd have other problems too if that were the cause.  Your oil pressure gauge wouldn't work either, and probably you'd have poor starting and running also.

My guess is that they gave you the wrong temp sender (or possibly a defective one).  They may have given you one for an indicator (idiot light) rather than one for a gauge. If you go to a NAPA store and get a TS6153, that should be the right sender, and it will work with your gauge, if everything is stock on your car.  (I'm assuming  this is a 289 with the factory gauges - if I am wrong, tell me and I may be able to tell you what sender you need).

Of course, you can always try grounding the block to the battery negative post with another wire, to see if that changes things, but if the engine still has the factory ground strap from the back of the intake manifold to the firewall, it should be well grounded.

I hope this helps,

Dick