Electric water pump will not turn on?

MARK MCCABE

MEMBER
1966 CHEVROLET CHEVELLE
7.4L
V8
2WD
AUTOMATIC
150,000 MILES

I have already done electrical troubleshooting, l’m decent at it. I have 12 volts at the switch and I also was able to spin new water pump on the bench with a jumper to my batteries in the trunk, the problem I have is the chassis wiring at the water pump is only reading 7.8 volts, so from cockpit switch to water pump wiring is breaking down?

1 Reply

CARADIODOC

MECHANIC
33,757 POSTS

Can you post a diagram of the circuit? Obviously this isn't factory, so I assume this is part of a kit or modification. Is there a fuse link wire involved? If there is, tug gently on it. It's good if it acts like a wire. It's burned open if it acts like a rubber band. Those have been responsible for many false voltage readings, even for very experienced mechanics.

If this is a very basic circuit with not much more than a motor and a switch, you may have better luck using an inexpensive test light rather than a digital voltmeter. That test light has to be an old, common one with a small incandescent light bulb, not one of the newer type with the built-in circuitry and voltmeter.

If you don't have a diagram, please describe the circuit, starting at the battery's positive post.