Electrical problem

95 Dodge 3500 4x4 cummins diesel.What would cause the tach,speedo,A/C and the alternator to stop working while driving down the road?? Everthing else operates perfect.Replaced the alternator and batteries.No change.The truck runs fine except for this recent problem.All fuses and relays good.Anyone have a clue??

[Shorts]

I don't know the schematics of the truck, but offhand I'd guess you've lost the VSS or VSSB (vehicle speed sensor/vssbuffer).

Some trucks have a gear thingy on the output shaft housing of the tcase right before the dshaft. Check that voltage that its working.

Or you could check the trucks speed sensor buffer which is probably near the computer somewhere.

I'm a chevy gal, so I'm picturing those parts, but again, not real sure on Dodges, but may give you something to go on.

Hi I had a 94 with a similar problem check the bus conecter at the back of the gauge cluster make sure they are tight and dont show signs of corosion