Instruments flicking back and forth

[James555]

I recently had the head gaskets replaced on my 2000 Sunsetter LXI.

Now all the instruments flick back and forth. The tacho is fine but everything else is haywire. Does anyone have any idea. I've tried sequentially disconnecting things with no effect. Could the computer be stuffed by the repairer.

Anyone have a wiring diagram?

Cheers

[grandude]

Possibly a loose ground. Double check ground connections at the engine block as well as the battery. if they are re setting constantly check the purple ignition wires on the key switch as well as orange wire on switch for good connection. Not much a mechanic could have or would have done back at the engine. POSSIBLY the cannon plug which is a round connection going into the side of the carbon covered box at the rear of the engine, Be sure it's plugged in tightly. He shouldn't have had to mess with this, but who knows what might have been touched. Are ALL functions jumping or only the oil pressure?

[MadMan]

All these gauges function by the sending units (fuel/temp/pressure) providing a path to ground. Since these are all separate circuits, it's probably not a grounding issue, they wouldn't all go bad at once. More likely it's the 12v power side of the gauges.

Edited December 4, 2015 by MadMan

[justgary]

Except that all the grounds connect at the stud on the back of the starboard head. Like grandude said, check to make sure that he didn't leave one of the ground wires off or loose when he reassembled it.

[grandude]

Since the tech would have no business under the dash for the procedure described I was leaning more towards a ground on the engine block or battery. After that as Gary suggests maybe move under the dash and check grounds. This boat will have a Medallion system so probably a single ground from the MDC to ground buss bar.

[James555]

Thanks all. I'll try them all. Appreciate the ideas