VOM don't lie but they can mislead. (probably not in the current range the gauges draw, BUT...)
(Numbers only for illustration)
You have a wire that has 19 strands and it can carry 10 amps you put a VOM on the end and you get 12V and 0 ohms resistance end to end. Take that same wire and attach an 8amp load to the end, the 12V is now 11V and you calculate the resistance of the wire (V/A = Ohm) 1V/8A = 0.125 Ohms.
You have the same wire but 18 of the 19 strands are broken but you don't know that at this point. It should be able to carry 10 amps you put a VOM on the end and you get 12V and 0 ohms resistance end to end. Take the damages wire and attach an 8amp load to the end, the 12V is now 3V and you calculate the resistance of the wire (V/A = Ohm) 9V/8A = 1.125 Ohms.
The thinner the wire the less current it can carry and when it tries to carry high current its resistance increases. A VOM measures voltage with no load and resistance with such a tiny amount of current about any wire size you can encounter will be negligible.
Be careful there. I destroyed an otherwise perfect gauge because the nut on the stud was too stiff to turn of easily and I spun the stud just trying to remove the stamped nut. NOW what I do is take 2 regular nuts and put them on the top of the shaft and jam them together. I hold them while turning the stamped nut. And don't use abrasives on the cir board traces, it starts a place for corrosion to develop, a pencil erasure will clean up the contact pads great
you can do it alone as 67Dart 273 noted. key off set up the jumpers. then get in the car and turn the key to run, watch for gauge movement then turn it off.
you can check it in 2 ways.
- measure the senders resistance with your VOM with the engine cold and then as the engine warms up. Use an infrared temp gun aimed at the base of the sender, not the manifold but the actual sender. keep measuring and record the values. greater than 70 Ohms ( 70 to 300 Ohms) is low temp cold engine, 23 Ohms would be about normal operating temp 160-200, 10 ohms is High (OH **** the engine just puked coolant high)
- remove the sender and get a pot on the stove filled with room temp water, suspend the sender pickup in the water (not the entire sender) hook up a ground wire and then measure resistance between where the sender wire connects and the ground. with a candy thermometer, turn on the heat to high and record the temp and resistance as the temp rises. you should get about the same results as above
They probably do BUT are the same manufacturer as aftermarket from the parts store. I bought a thermostat from dealer and it was an AutoRad thermostat with the same markings as the parts store but 5.00 more. I bought a steering wheel clock spring from the auto parts store and it had the exact markings as the OEM I pulled out.
the temp GAUGE sender is 2426458
The temp SWITCH sender is 3744253 (if you trust the hand written note)
View attachment 1716392055
Googling the part number has many results and I suspect Amazon or your local parts store will do the same.
View attachment 1716392059
