Vacuum to front hubs

[f100cleveland]

My auto hubs don't work in auto mode. They work if I turn hubs in manually. I have a hand vacuum tester and hubs engage when I put vacuum on the line to hubs and I have vacuum from pump to vacuum switch on inner fender. The switch has three wires on connector with the middle having 12 volts. Is the switch on the dash suppost to send juice to one of the other wires to make the vacuum switch work? Is it fused somewere? Sure is nice when they work without having to get out.

 

[DaveBen]

Did you check to see if you have vacuum at the hubs and then flip the switch and check it again. Usually there is a broken or loose vacuum hose at the front wheel. I have not heard of the vacuum/electric solenoid going bad, but I am sure they do.

Dave

 

[f100cleveland]

Checked for broken or loose lines but from switch to hubs it holds vacuum. If the switch has 3 wires and the middle is hot is one ground and one switched 12v?

 

[RJDiesel]

I have the auto hub problem on my F250 also, when I engage the switch my hubs will engage but after about 10-20seconds the hub disengages, we found a small vacuum leak and will be replacing the seals in the spring.

 

[f100cleveland]

Have a friend that copied me the mitchell manual on auto hubs and ended up being 141 pages of in depth detailed trouble shooting. From what I have found out so far I think my gem module is bad or a connection to or from it. Thanks to Ford for putting manual locks on too. Think I'll wait till it warms up then work on it.