I've read many other threads on this, but I've not been able to put together my next step.

I'm not concerned w/ the vacuum portion of the system. I have locked the hubs manually for some time. But recently the 4x4 has quit, and I no longer hear the transfer case shift and the dash light doesn't lite up.

I tested the 2 fuses in the cab and the 1 under the hood. I put a test meter at the shift motor (2 wires), no voltage when someone else turns the swith to 4H. Changed the 2 relays next to the battery with the relays for the trailer plug. No action.

What should I test next and how. Did I read that the relays can be used in place of the electric window or something else to determine if they are good. OR how can I test the relays? What should I look for after this? How can the dash switch be tested? Where is the GEM located, and can it be tested?

TIA, SilverDollar

Early '99 F-350 PSD

 

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