Dash lights....AGAIN!

[OzMach1 10]

G'day from 'Down-Under'guys, long time reader, first time poster!

 

I recently imported an 'M' code Mach 1 and have been reading some great advice on here about dash light problems. Unfortunately, I am also a victim of this problem, and I was hoping you could help. The dash lights have not worked since I have had the car). All guages and lights that function on the ignition circuit are fine. I have no dash lights, nor others on the Blue/Red circuit (Clock/heater lights). In accordance with the circuit diagram, circuits are fine from fuse block to light switch and I am getting 12v from the light switch on the first click (light switch is new). I am not getting 12v to the connector at the instrument cluster, nor the clock or heater lights.

 

One curious thing that happened yesterday was that I got an intermittent 12v reading at the cluster connector (for a second) when I depressed the tilt away switch on the drivers side. Maybe a red-herring, but it's the first time I've seen life at the blue/red wire at the instrument connector (the tilt away is not working, but clicks when depressed when ignition is off). I am going to recheck circuits between the fuse box and the clock lights, but I reckon it was ok and has been checked.

 

I assume that the new light switch is ok, PCB earth's for globes are good (all other lights work and earth to the same part of the PCB, and all globes are fine).

 

Recent advice was that the new light switch was to blame but I'm not convinced as yet as I appear to be getting 12v out.

 

Am I on the right track? What do you think?...:helpsmilie:

[PaleRider 12]

I'd bet on headlight switch - 2 different 70's - had to replace switch to get dash lights working.

[foothilltom 33]

Howdy Oz, I would tend to agree with PaleRider that the most likely suspect in general would be the light switch for the symptoms you're describing. I will be replacing my light switch quite soon in my coupe as i'm getting intermittent on/off behavior with dash lights and I can fiddle with the switch to cause it to flicker.

 

Your situation sounds a bit more dodgy as you've already verified 12V coming out of the switch. Some good tests would be to shunt a wire across your various switch terminals to "bypass" the switch and supply 12 volts directly to each terminal There are a helluva lot of terminals on my switch i'm holding, but I think you get the idea. You could easily implicate the switch if you get any lights to come on by bypassing the switch.

 

If your lights don't come on by bypassing, I would tend to lean toward a bad printed circuit board, or perhaps just a crusty fuse panel. My memory of my son's coupe project are growing more dim by the day, but I recall solving some dash light gremlins by simply removing each fuse in turn and cleaning the contacts in the fuse panel. If the fuse looked old, I replaced it.

 

When my boy's dash lights were a problem, I had the entire instrument cluster out on the bench and was individually testing the lights. While I had it out, I replaced the crappy incandescent bulbs with LEDs. It was nice having it out to convince myself that the circuit board was fine. Only later did the simple fuse thing occur.

 

So, in short:

 

* Try isolating your switch by bypassing circuits

* Suspect fuses

* Suspect printed circuit board (this is a bummer)

* Suspect bulbs (all of them bad is unlikely)

 

Good luck,

Tom

[OzMach1 10]

Thanks a lot guys. Firstly, I'd suspect the headlight switch too - just find it hard to believe that the new one is faulty.

 

Tom - all the bulbs are good, and the cluster is out of the car. I'm under the impression that there still should be power to the b/r circuit even if the cluster (and PCB) aren't connected. Incidentally I'm replacing the PCB as well.

 

I'll certainly give your other ideas a go, and let you know the outcome. Thanks again for taking the time.

 

Al

[kazlaszlo 10]

All the above makes good sence, I would replace the fuses,often they look good but old and disconnected.

Also check the main plug in the back of the circuit board, make sure that the following wires are properly connected; ( non-Tach circuit board )

57 $ 57A Black , ground to pin #8

19C Blue/red . dash light . pin#12 ( 19 originates at the headlight switch, goes to the fuse box, then to the big plug, pin #12 on the back of the circuit board.

30 Violet, 12V from Ign.A. to pin#11

 

Kaz

[OzMach1 10]

Thanks Kaz!

 

Update: The dash light circuit was shorting on the stereo earth of all things!! Somebody connected the stereo earth to the circuit. Lots of frayed wires too, that were exposed within the harness. Light switch was ok and the circuit works now. [insert 'huge relief' here!!]

 

This has raised a couple of other questions though, if I may:

 

Where is the physical location of the ignition switch light? I think I have located the wire.

 

Also, whilst re-installing the heater light, I broke a terminal off a little red/maroon coloured switchy thing. Probably about 1.5" x 3/4"x 1/4", on top of the heater box, and held in place by 2 small bolts. Looks to have 2 terminals (light green/yellow I think) Looks to be actuated by the temp control. The car has factory air - I'm thinking its aircon related. Any idea what it is, and what to specify for replacement?

 

Thanks again.

[OzMach1 10]

Here's a pic. You can see the terminal I broke off in the foreground.

 

Anyone know what it is?

[LoneWolf2U 136]

Looks like a rigged Ac switch. it prob turns on the compressor.

[OzMach1 10]

thanks 'Rider'...took one off another 69 heater temp control yesterday. Its a micro switch for the compressor. Wired into fan switch and the compressor. Standard fit.

 

Just be careful if you're tinkering around close to it (as I was) as the terminals can be brittle. Very fiddly to replace without the heater control out.

 

Thanks for your help guys.