Here's the symptoms on my 90 convertible:
1) Pull back the stalk to turn on high beams, nothing happens. When lights are off, the flash-to-pass function works. I checked the stalk switch and it functions ok.

2) I can put a negative ground to the dimmer relay under the hood and the high beams come on, so I know it's not a relay problem or bulb problem.

3) The negative ground from the dimmer stalk/lever is not making it to the dimmer relay under the hood. Somewhere between the two the connection is lost.

4) The diagram shows a latch circuit for the dimmer switch being in the cluster switch, but I have swapped the headlight cluster switch with another and it does the same thing.

5) HERE IS THE STRANGE PART! A few times the seatbelt warning chime started working, which it never did before. When it was working, the highbeams started working. I could go a few minutes and then the high beams would go off. At the exact same time the seatbelt warning chime would quit working. This makes me think it's a CPU problem, but the service manual doens't show the headlights going though the CPU.

HERE'S the FSM schematic. Anybody experience this? What's the next thing to check?

 

One thing I need to check is the ground going to the cluster switch, although the lamps in the cluster switch itself seems to be working ok.

 

The cluster switch is getting ground. I messed with it for two hours and still no luck.

 

^^^^^^^

 

Hapened to me once, and it turned out a fan cut through the wires to the headlight relay.. not saying thats common but its worth checking, took me a week to figure it out.

 

just had the same issue, I just replaced the entire turn/high beam switch and now everything works...might want to look into it.

 

Schmol, Is your car a coupe or vert? it's different on a convertible.
The switch is on a stalk off the steering column. There are no electronics in the switch itself, only contact points. Everything on my turn/highbeam switch seems to function when I check with a multimeter.

 

im having the same problem in my vert, but i havent started looking into it yet. im probably goin to start on it in a couple of weeks. please let me know if you figure any thing out.

 

I had the same problem. I searched, did trouble shooting checked all the things you checked. Icemark had the answer. The headlight does go through the cpu on the Vert with airbag. That is mostly 90 and 91. I think that the diagram you have is not correct for this year.

I fixed it with a new FC66 CPU. Do not use any other number. You can also just buy the flasher board.

http://www.mazdatrix.com/getprice.as...m=67-5640-FB01

This fixed it 100%, and yes, the seatbelt chime now works as well.

good luck!

 

I knew somebody had to have had this happen! Thanks. I had the CPU out and apart looking for something obvious. I didn't really see anything smoked, so that's all I could do with it. I'll see if I can find a FC66 CPU. This was my original guess since the seatbelt chime was going in and out at the same time. Just no real way to test it without having another part to swap in.

 

I took a second look at the CPU and there were a couple of components damaged. Guess I'll be getting another CPU. The board looked a little too burnt to try to just replace the component.

 

I had the exact same problem, It ended up being the dimmer relay. Got it from mazda for 20 bucks. Hope this helps. I dont know what everyone else is trying to explain to you, but thes the problem. The relay is located under the hood in the middle part of the nose along with some other relays.

 

It's not the dimmer relay. The relay functions properly. I can put a ground to the white wire of the dimmer relay and the high beams come on. I hoped that was the problem, as it is the logical solution. The real problem is the fried circuit you see above on the BCM. It's only on 90-91 convertibles with air bag that the lights go through the BCM.

 

ok sorry!! goodluck then.