Water pump blowing fuse

[JohnMyers]

I have a 2006 Charleston. On the way back from TX my water pump starting blowing the fuse located in the compartment under the driver. The pump will start and run for a very short time and then blow this fuse.

It does not blow the inline fuse by the pump. I have replace the switch and this did not work.

Any thought of what to check next.

[papap]

May have a short in wire going to pump or pump is going bad.

[JohnMyers]

I have checked the wires and can not find a short. If the short is in the wiring harness I am not sure if I could find it. If I turn the pump on and let it run it will work for 4 to 5 min. and then blow the fuse on the fuse panel. I can not find a wiring diagram for the coach so I am not sure were to start.

[jimh]

sense the fuse at the pump is not blowing, i'm inclined to believe a short. the other thought is that you have more than one thing on that fuse.

shorts can be interesting anamals; i would try and trace the wire and see if there is an exposed part rubbing on a metal part. if u have a tester, u can disconnect the fuse at the pump. then pull the fuse at the fuse panel (determine which is the hot side) then check the resistance to ground from the pump side of the fuse back. if it isn't open, then u have a short the wiring to the pump.

if u have to check at the fuse panel, i would test the volt side first to make sure that i was not on the 12 volt supply side to the fuse.

this won't help u now, but i bought a amp meter from harbor freight that u plug into the fuse holder, put a fuse of the correct value in the tester. u can read current being supplied to pump.

i'm also assuming that the fuse in supply is as large or larger than the fuse at the pump. the fuse at the panel is there to protect the wire and should already be the correct size.

if the fuse at the fuse box is smaller than the fuse at the pump, i would suspect the fuse at the pump had been changed to a larger size to keep it from blowing...not what u want to do.

[jimh]

if u have a tester with a light, u should be able to pull the fuse with the pump off and check the terminals that the fuse plugs into. if u get a light, u have a short. if not, it shouldn't light. u can also use a volt meter across the terminals the same way. u normally shouldn't have a path to ground with the pump off. if it checks that it is a short, i would disconnect the fuse at the pump and run the same test again at the main fuse panel.

this should tell u that there is a problem with the wire. if it shows a problem, i would suspect a short in that wire or something else on that circuit.

[Great Horned Owl]

If the fuse blows when you turn on the pump switch, then you might suspect a short. If it blows when demand causes the pump to try to start pumping, then the problem is most likely the pump. Feel the pump body and see if it seems hot.

The fact that it is the fuse in the panel that blows rather than the one by the pump could have several possible explanations. Are both fuses the same amp rating? If not, the lower rated fuse will be the one that blows. Are both fuses the same type? Different types of fuses have different time/current curves. With a given amount of overload, one type can blow significantly faster than some other type. Some are even designated slo-blow.

One other thing to check is if the fuse that blows has other loads connected to it. You know that the one at the pump does not.

Joel

[JohnMyers]

I think I found the problem. I talked to the factor and they advised it could be a switch relay that is located in the compartment with the fuses. I changed out the relay and all seems to be working fine. One word of caution on changing the switch relay ( my unit has three all in a bank) make sure the relay you get is exactly like the one you take out. I got one from an auto parts store and it did not work. one of the numbers was off by one. I went to Freight Liner and got the right one.

Thanks to all to responed