Headlights Won't Dimm!
 

Here's a problem I've searched the archives to try and get a clue where to start and haven't found my symptoms. The car is an unmolested '87 coupe.

The car's headlights work fine. When I pull back on the turn signal stalk the brights are activated and my blue indicator lights as it should. However, when I pull back on the stalk to unlatch the brights nothing happens. The only way I can unlatch the relay is by cutting power to the headlights by switching them off with the main switch. Unacceptable as far as my state is concerned so I can't pass inspection till I figure it out.

Hep me!
Hep me!:scratch:

Should I just tear open the turn signal switch and look for something mechanical.

Since the lights work as they should, it has to be the switch.

I pulled the switch and opened it up. It turns out the mechanical portion of the circuit is just a spring-loaded, single pole switch. So since the high-beams latch on flawlessly every time it can't be that. Dang, I was hoping this would be simple!

To add to my frustration the manual has nothing but a box titled "latch cct" where there is supposed to be wiring detail. All the other gizmo's have some circuit detail but not this one.

I found a wrecking yard on eBay selling the switch assemblies for $30 so if I screw this one up I guess I have a reasonable escape.

I've also ruled out the relay because the high-beams latch. I'm thinking it has to be a failed transistor or something in the latch circuit. I just need to draw out the circuit and figure out how it works. Thats not easy because there are 3 different PCB's and the turn-signal circuit is mixed in.

While I've got the cluster torn apart I've decided to replace all those tiny burned out 1 watt lamps. Digikey has them (8640JK) for only 16 cents a piece (but it's a minimum order of 100, D'oh!) Anybody found them local?

I'll update the thread however this thing gets resolved.

From looking at the wiring diagram you have probably concluded that the role of the dimmer switch is to provide a ground signal to the dimmer relay to turn the brights on and then removing the ground signal to the relay to dims the brights. The part of the switch that is working in your case is the ground signal being provided to the relay but not the removal of the ground signal for some reason. Kind of strange. Good luck in figuring it out.

As far as the bulbs, are you talking about the bulbs that are in the switches or in the back of the gauge cluster? If it's those in the switch, I can help you out. I ordered 100 from a different vendor awhile back to replace all of mine.

Thanks for offerin! PM sent.

Sounds to me like the high beam is out. They are two different filiments aren't they? I don't have stock headlights anymore so I don't know what's supposed to happen (if when you hit the brights, the low beams turn off). Maybe just take a quick look at the bulb to see if you see two filiments.

Here's an update on this issue. I took the dimmer/turn signal assembly apart to get to the circuit boards. I gave up trying to draw the circuit. Instead I just tested every component which turned out to be much easier. Resistors and diodes were all good. I found a 100microFarad capacitor that looked blown so I removed it from the board and retested it. It passed on the retest but I replaced it anyway thinking it might be an intermittent thing. I tried to test the tiny transistors but didn't have much luck while they were on the board and I figured I'd destroy them trying to get them off (surface mount technology). So, feeling a bit frustrated, I lubricated the slide contacts and put it back together. After installing it on the car it WORKS! To be honest I'm not sure what I did to fix the damn thing. I worked it through about 20 cycles and it seems to be working fine now...

On one car I have a small problem with it working.
To make it work right I find that if I just flip the switch with my finger quickly it works.

If I use a normal deliberate flip of the switch it does not work.

So I just don't use a normal deliberate action. I just flip the switch quickly and it works. Even for the safety inspector yearly.