Water Pump Blows Fuse

[Danno99]

When I turn on the water pump switch it blows the fuse. I connected the pump to a car battery and it's turning over so it doesn't appear to be drawing too many amps. I left the pump disconnected and it still blows the fuse. I'm hoping someone with experience can help me out. Thanks in advance!

[vintagemotor]

You have a short, in your switch (hopefully) or in the wire harness between the switch and pump. Disconnect the wires (cut) from the back of the switch, turn on the switch and hope it still blows the fuse, otherwise you are looking at the wire harness shorted somewhere.
Good luck and happy airstreaming!

[Danno99]

Thank you for the response. I'll give it a try and see what happens. I'm hoping you're right and it's not the wiring harness.

[rmkrum]

Another thought.

The pump motor may turn over when you have it connected directly to a battery, but that does not mean it is working correctly.

Try the same test with the same rated fuse in the Airstream pump circuit in series with the battery. If the pump motor is going bad and drawing excess current, the fuse will blow. If it runs properly without blowing the fuse, its probably good.

[Danno99]

Good point rmkrum. I'll give that a try as well.

[A W Warn]

In post #1 you said "I left the pump disconnected and it still blows the fuse." If flipping the switch with the pump out of the circuit still blows the fuse, that eliminates the pump as the problem. Only things left are switchs or wiring.

[rmkrum]

True that...

Worth a check--as a bad pump can eventually toast wiring as well...

If it is a wire in the wall, it's going to be a mother bear to find the problem or replace the wire...

[justplaincor]

Can I jump in with another pump question here? I picked up a ‘75 Safari 23’ with the original water pump. It was working when I left, but now fails to turn. Breaker is fine, fuses look fine in the 12v box, and the switch light on the panel comes on when I flip it. But alas. No pump action. I was gonna Jam my head back in there when I got a free minute to see if anything banged loose on all the driving I’ve been doing with it. Any advice is appreciated. :-)

[rmkrum]

Inspection is the first thing. Look for loose 12 volt supply wires between the switch and pump. Check for a properly-connected ground wire as well. Closely inspect for corrosion and toasted insulation.

Verify that the pressure switch on the pump is working properly--it should be closed (so power will get to the pump) when the pressure is low.

If the pump motor has obvious brush holder caps, pull the brushes and see if they are the right length. Most pumps I've seen don't have brush caps, but a look doesn't hurt if it has them.

All else fails, pull the pump, try it with a properly rated fuse in series and connect right to the battery. If it then runs, the issue is somewhere in the wiring.

[Danno99]

Originally Posted by rmkrum

True that...

Worth a check--as a bad pump can eventually toast wiring as well...

If it is a wire in the wall, it's going to be a mother bear to find the problem or replace the wire...

I’m going to pull the switches this weekend to see if that’s the problem. I fear that it is the wiring in the wall and like you said it’s going to be a pain to replace it.