M1078a1p2 electrical problem

[SailBoat]

Brought said truck in to do a service on it and now everytime you cut any of the lights on ( Ser. Drive, blackout lights, etc) the wipers come on. It also runs the wipers when you press the air horn button. Everything looks and checks out good from the switches and relays. I can’t just pin point the short if it is one. Hopefully someone has had the same problem.

 

[Ronmar]

I would suspect something is shorted in the turn signal switch wiring…

 

[SailBoat]

Thank you, trying to trace the wires now but also noticed the main light switch is sending power to both the headlight relay and wiper relay. If that helps any

 

[Third From Texas]

Thank you, trying to trace the wires now but also noticed the main light switch is sending power to both the headlight relay and wiper relay. If that helps any

Have you inspected the wire loom under the dash, etc. Could always be a wire chaff/burn/short I suppose.

 

[GeneralDisorder]

Disconnect the turn signal switch and see if it stops?

 

[SailBoat]

Have you inspected the wire loom under the dash, etc. Could always be a wire chaff/burn/short I suppose.
[/QUOTE
From what I see that’s visible the wires look fine but I won’t know the rest till I take out the rest of the dash

 

[SailBoat]

Disconnect the turn signal switch and see if it stops?

Disconnect the turn signal switch and see if it stops?

Tried that the wipers won’t run with the lights switched on but the headlights won’t either but the dash thinks there on

 

[GeneralDisorder]

You can sort-of disassemble the end of the turn signal stalk - where the washer function sleeve is. Pull that off and inspect the contacts...... you probably need to replace it. Does the horn and washer function work? Welcome to German plastic truck controls.....

 

[SailBoat]

You can sort-of disassemble the end of the turn signal stalk - where the washer function sleeve is. Pull that off and inspect the contacts...... you probably need to replace it. Does the horn and washer function work? Welcome to German plastic truck controls.....

Checked the contacts nothing looked corroded and there making contact. I also actually replaced it with a known good same with the main headlight switch and little disruption box and still have the same problem. I’m thinking the wire might be chewed up behind the hvac box. And the washer works but the horn activates the wipers even with the good switch. And oh I know I’d much rather take a torch to it

 

[NotThatGuy]

Brought said truck in to do a service on it and now everytime you cut any of the lights on ( Ser. Drive, blackout lights, etc) the wipers come on. It also runs the wipers when you press the air horn button. Everything looks and checks out good from the switches and relays. I can’t just pin point the short if it is one. Hopefully someone has had the same problem.

I suspect a possible BAD GROUND CONNECTION somewhere.

when you cycle a DC Item and a different and isolated circuit activates it means that the Ground Return on Circuit #1 is faulty and sought out the nearest/Easyest pathwat to Ground to complete the circuit.

Note: Even when a DC connection appears good anf tight microscopic corrosion can cause an impedence enough to inturrupt/break the connection.

If you don’t know how to meter out and trace DC Circuits i
Id recommen the following.

1) Clean and instal dielectric grease all Battery Grounds and connections.
2) Clean and install dielectric grease at all Ground connections at the fuse panel.
3) Clean and install dielectric grease at all electrical connection in the circuits that are malfunctioning.
4) Charge and Load Test all Batteries.
5) Inspect and Load Test
Charging System.

 

[Suprman]

Maybe bad ground and power feeding back somewhere

 

[GeneralDisorder]

Yes - possible ground is another good call - check the one that's on the same part of the harness as the washer fluid pump. That one is involved in the headlight circuit. It's inside the driver's step on the older trucks - not entirely positive where it's at on the A1P2 without looking at one but I can't imagine it's far.