MrBleeble

I replaced the headlight switch and the hi beam/dimmer switch about 5 months ago because only the parking lights would come on but no lo beams and the hi beams wouldn't come on either.

So, this morning, no lo beams, only parking lights, but the hi beams still work (apart from the outermost passenger side light) when I pull the stalk. I changed the passenger's outer headlight bulb, but after checking it was just the same.

The first thing I can think of is the headlight switch, but having replaced that a mere 5 months ago I would hope it would be something else, especially as it was a royal PITA to replace. As luck would have it I still have the original headlight switch because changing it fixed nothing last time, it was the hi beam/dimmer switch so I imagine it still works.

I also noticed that the plastic cover to the C100 at the firewall had come off, and there was still some of the black grease on the wires, but it looked clean enough, so I put the cover back on.

If the hi beams still go on and off, would it most likely be the headlight switch? I thought maybe someone else had this combination of symptoms and could say for sure what fixed it to save me a few hours of messing around.

Thanks

MrBleeble

OK, so today I switched back to the original headlight switch which wasn't the culprit last time but I changed anyway. Same exact thing.

There is power coming from the yellow wire on the headlight switch connector when I pull out the stalk all the way, and the hi beam stalk switches the hi beams on and off, but still no headlights.

Does this mean that there is a break somewhere between the dimmer switch and the lo beams themselves? Somewhere in that tan wire? (since the hi beams work I must have power to the green wire, right?) I will check that tomorrow when I have some free time.

MrBleeble

Today I investigated further.

There is 13.something volts from the yellow wire at the connector going into the dimmer switch.

There is 0.13v coming from the tan wire on the dimmer switch connector when I turn the lo beams on (and the same when I pull it once for just parking lights), which doubles when I pull the stalk for the hi beams.

I also checked for continuity between the connector and the tan wire as the connection looked a little "pulled out" but there is definitely continuity there.

The green wire has power as the hi beams light up.

Does this point to a bad dimmer switch? Last time I just went for the "standard motor products" cheapo one, should I replace it with a delco one?

NINÅ

MrBleeble

Hi Nina, thanks for the reply.

If there is any confusion: "Full beams" is what we call high beams in the UK. I guess I slipped into UK talk for a minute there.

The dimmer switch clicks when I pull the stalk, lighting up the high beam symbol on the cluster, and putting the high beams themselves, on. The high beams work, just not the low beams.

If the dimmer switch clicks like it should, would I still have a chance of getting the lo beams to work by adjusting it?

NINÅ

MrBleeble

For future readers of this thread, it turned out to be the dimmer switch. Replacing it fixed the lo beams which now come on when I pull out the headlight switch all the way as they should.

Thanks for your help Nina.

However, now when I flick the hi beams on, the passenger side lo beam goes off. The driver's lo beam remains on (and I guess the hi beam filament lights up too) but nothing at all from the passenger's headlight when the hi beams are selected, no lo or hi from the outer light but the inner hi beam lights up (so, when I flick on the hi beams, of the four lights, picture just the three on the right lit).

Where do I start with this?

greggbruce

iTrader: (1)

to look up the proper wiring diagram, is it a berlinetta or a sport coupe?
they seem to be different

MrBleeble

Thanks for the reply.

It's an 84 Z28 as mentioned in the title.

This is (I think) the relevant wiring diagram:



Another:



The problem is, I don't have a clue what I'm looking at as I'm extremely new to the whole car electrical DIY game.

What I don't understand is how the headlight works with lo beam but then completely shuts off with hi beam. The previous problem led to me confirming that the headlight switch works (same problem with 2 different switches), and the dimmer switch is a brand new ac delco replacement.

Any help would be appreciated.

greggbruce

iTrader: (1)

yep, sorry, missed the z28 part....
I show the first pic is supposed to be yours (but it doesn't show very well), and if that is the case, I would think the problem is either a filament in the bulb, or the socket for the passenger low beam. Headlamp Wiring Circuit1.pdf

MrBleeble

I have done some further testing/observation of the beam etc.

What appears to be happening is that when I put the lo beams on, I get lo beams on the driver's headlamp, but both filaments come on on the passenger headlamp. When I flick the stalk for the hi beams, I get hi beams on the driver's side (both lamps on), hi beams on the inner passenger side, but nothing from the outer passenger's headlamp.

Surely something must be crossed somewhere....

greggbruce

iTrader: (1)

try switching the low dual filament bulb with the other side and see if the problem changes sides, if it does, it's the bulb. if not, it's the connection(s) of the passenger low beam socket. What's happening is the low beam is grounding through the second filament and the high beam bulb which means the socket is not providing the ground at the low beam itself.

MrBleeble

OK, thanks for the reply. I think I shall just try a brand new bulb first as I have switched a couple in, same thing.

I will also try switching in some brand new sealed hi beams.

MrBleeble

Today I replaced the inner lamps with new h4651 sealed beams. I also cleaned out the socket for the passenger headlamp (which are Hella projectors, not sealed beams) with contact cleaner, and replaced the bulb with a brand new Bosch bulb which slid in nice and easy compared to the old one which I took the skin off my knuckle removing.

Still the same thing.

It probably won't hurt to mention, that in order to be UK legal you need white front facing parking lights (which we call "sidelights") which I had installed in the headlamp units. These are wired to come on with the parking lights. However, on the passenger side, while they work as they should with parking lights selected, when I select headlights, the passenger side "sidelight" does not come on (and both filaments of the headlamp bulb light), but with hi beams selected, it comes on while neither element of the headlamp bulb lights.

The driver's side lights are working correctly.

Where do I go from here?

greggbruce

iTrader: (1)

sounds like a ground issue. I do not have wiring diagrams for UK stuff, sorry, forgot that's where you are at. Find where the lights ground to the body, check resistance from bulb socket to ground should be less than a few ohms. If the ground is not broken, remove it from the body, sand the body and the ground connector and re attach, make sure it is good and tight, recheck operation.

greggbruce

iTrader: (1)

it sounds like the wiring would be different for the UK car.... if there is a diagram for that, ( if it's different from the one you already posted) I would be happy to look at it and help.

MrBleeble

Thanks, but it's an imported car, most definitely US built from the VIN. The steering wheel would be on the other side if it was a UK car The only difference is that the outer headlamps have been upgraded from sealed beams to H4 projectors, but the socket should still be the same, and there are white bulbs spliced from the front parking lights as I mentioned before, and the orange front parking lights are rewired as turn signal only.

The headlamps still take the same tan, green and black wires. The white lights take a red and a black.

Thanks for the latest suggestion. I will check out what you said when I get some free time.

I guess I can take pics to clear things up if you like.

greggbruce

iTrader: (1)

pics would help.... yes.