Headlight hi beam/lo beam switch question

Vehicle: 1983 chevy c10

Heres the problem, when the high beams are on the dash cluster lights work fine,but when I turn the high beams off the dash cluster lights go off. Im going to buy a new high beam switch but what else might cause this problem?
The truck has one of those metal button high beam switches that is mounted on the floor.

Sounds more like a ground problem, ie, a corroded ground connection. Or some other connection…

You need to track down the problem with a voltmeter.

Yes @BillRussel it does sound like a faulty ground and when the lights are on high beam the dash illumination is grounding by back feeding through the high beam indicator.

As others suggested the trouble seems to be with the grounding somehow for the lights. I doubt very much replacing the high/low beam switch is going to correct the problem. What little info I saw showed a couple of black ground wires going to the instrument panel connector. Make sure those wires have no voltage on them at the connector while the problem is happening. If you do see voltage that means that wire is not making connection to ground.

ok, so I replaced the dimmer switch, the light switch, and cleaned the ground wire connections at the headlights and the ground for the dash harness by the emergency brake pedal.
Both of the high beam lights work now whereas before only one of them worked,but the dash lights still will only work when the high beams are on.

I have the emergency brake light switch unplugged is it possible that the dash lights ground through that? I guess tomorrow Ill reconnect it and see it that fixes it. another thing I noticed is that the high beam indicator light on the dash never comes on.I put a new bulb in it but it still doesnt come on when the high beams are on.

I read that if any of the rear running lights are burned out that the dash lights won`t come on, is that true, have you ever heard of that?

one other thing, is it possible that I have the dash cluster wiring harness plugged in the wrong way or is there only one way that it will plug in?

Where did you read that the dash lights would not come on if the rear tails don.t work ?

Did you clean the chassis ground for the battery also? The dash lights wouldn’t ground through the E-brake light circuit. At this point it seems to me you are going to need a factory service manual for the wiring and a meter to make tests with. I suppose there could be damage inside the cluster that is causing the high beam light to not work. I assume you have already made sure that the connectors to the dash are making good solid connection.

“is it possible that I have the dash cluster wiring harness plugged in the wrong way” ?
A visual inspection of the connector should answer this.

There could be a break in the printed circuit.

“Where did you read that the dash lights would not come on if the rear tails don.t work ?”

From my experience, I remember this was true (at least with GM) from vehicles a few decades ago.

I bought the truck a few months ago,it needed a lot of work,but I never drove it at night until a few weeks ago so I don`t know if the dash lights even worked when I bought it.

The weather is suppose to be spring like today so Ill be out there all day or until its fixed.i`m going to pull the instrument cluster out and start from there checking the harness,the printed circuit,all the ground and power wires with a meter.

I guess I`ll reconnect the parking brake switch for the dash light and check the tail lights, for the heck of it.

When testing for bad active grounds they should have no voltage across them when using chassis ground as your meter reference point. You can also use a jumper lead to make your own ground connection to things you suspect aren’t getting to a good ground point. Just make sure that the point is supposed to grounded.

today I started at the battery and double checked all the grounds from the battery and the headlight grounds, I made sure they were all clean and tight.
I reconnected the parking brake switch for the parking brake dash light.
I disconnected the harness from the dash cluster and cleaned all the connections.

The parking brake dash light works.
When I turn the high beams on the dash light for the high beams comes on now and the parking brake light stays on, but none of the other dash lights come on now.
I removed the bulbs that weren`t on and checked the voltage, zero volts.
I checked the bulbs that were on, they had about 11 volts.

I removed the printed circuit from the back and noticed that the plastic is separating and theres green corrosion between the plastic, so Im going to replace it.

It has a new problem though. When I turn the high beams on all 4 of the headlights flash on and off at about a 2 second interval.When I turn the high beams off the low beams stay on and dont flash. The running lights dont flash when the high beams are on it`s just the headlights that flash.

When the headlights flash on and off it is likely that the circuit breaker in the headlight switch is being overloaded. And with all these issues regarding your headlights I suspect that someone might have done some re-engineering in the past. Are there fog lamps or spot lights on the truck or even hole drilled where such lights were once installed?

I think @Rod Knox’s comment about the circuit breaker for the headlights is spot on since having all 4 lights on at the same time is most likely causing an overload situation. I have to wonder if you somehow made a mistake when you reconnected things back together. Also check for any blown fuses.

It has to be the passenger side high beam thats causing the problem, because the passenger high beam wasnt working until yesterday when I cleaned the ground contact for it.
The ground wire coming from that high beam is connected to the negative terminal on the battery.
The high beam on the drivers side is grounded to the radiator support frame.

its dark now but Ill go out tomorrow and move the passenger high beam ground wire from the battery and ground it to the radiator frame like the driver side one is.

it does have 1 burned fuse, its a 5 amp fuse Im not sure what else it`s for but the dash clock was connected to it

The wiring diagram shows that the 5 amp fuse is for the instrument cluster.

Possibly the feed back from the high beam indicator is powering the instrument cluster lights rather than grounding them as I first supposed. Replacing the 5 amp fuse might solve half the problem.

@Nevada_545 OMG! are you serious? well that would explain why the instrument lights don`t work anymore even with the high beams on.
I must have blown that fuse when I was cleaning the connector on the harness.I used a little screwdriver to bend the metal prongs out because there were pretty flattened.

Ill get a new fuse tomorrow and put it all back together and see what happens. Ill still get a new printed circuit because the plastic is starting to peel apart and it`s getting a little green.

@red knox, yeah, because even with the blown fuse the high beam indicator on the dash still worked as well as the parking brake indicator light. those 2 lights must be feed from a different circuit.
I wonder if that might have something to do with the circuit breaker tripping with the high beams on? if the high beam circuit is feeding back to other places it could be drawing too many amps causing the breaker to trip.