Map Light Switch Question
 

Well, it's starting. I have the '91 convertible home and in the garage. ROM on order. Experience in a Book read so many times it's almost memorized. Ready to bleed brakes, change all hoses and belts, and otherwise trying to figure out what I have, and what I need to do.

Actually, first order of business is to get rid of the mothball smell. It seems the PO was nervous about mice. At first, I thought the trunk smelled like gas (and I'm still looking for the charcoal canister), but that will be solved in time. Meanwhile, back in the cockpit:

My map lights do not work. I tested the bulb, so I know it's not that. Pulled the switches from the dash.

I know I have power to the switch, because I can see the switch light turn on with the headlights. I don't know if there is actually power to the switch itself, or how to check it. There is a red and black wire in the centre of the switch block. I could not get a voltage reading across these two wires, but did get zero resistance between the two. I can't tell if these wires power the switch, or just the bulb in the switch.

When I pulled the switch out, there seems to be a "block" of (if memory serves) purple wires going to the bulb. Continuity check shows this part to be good.

However, continuity within the switch itself does not seem to be there, on or off. But it seems odd that two map light switches are both blown, but all other switches (defogger, hazard, windows, top, cruise control, even the heated seats and lumbar support) work flawlessly. Am I doing something wrong in testing? Chasing shorts is new to me. Suggestions before I just buy switches and throw money at the problem?

Don't have a schematic in front of me, but as a general rule of thumb on these cars, if something doesn't work check the relays.

Do they come on when you open the doors?
Greg

You're not doing anything wrong, per se. The interior light circuits are a bit fiendish---more so than most cars. When you see the diagram you'll know what I mean. It's a tricky circuit to figure out.

I do know that the solid purple wires are voltage directly from the fuse. Purple/white are grounds from the door switches. I think the other purple/xxx combinations are voltage from a switch.

Hopefully someone can post a '91 diagram for you.

Convertibles are different then coupes, by the way, in terms of the interior light circuits

Cheers
DD

No, they do not.

Thanks. It sounds like a tricky circuit, and I did notice that "switch 2" has a different number of wires leading to it than "switch 1".

What I don't understand is which "pins" the switch activates. It seems that I should get some continuity between pins when the switch is in, but I can't figure out which.

As far as checking relays, that makes sense... but I'm not sure where they are hiding.

I do not think there are any relays in the courtesy light circuits. Next question, does the centre roof liner light work when the doors open? It has three positions, off, on, and on when doors open, all activated by swivelling the glass front to back.

Also, check if you have power to the door jamb switches, by unscrewing the unit and carefully pulling out the switch. Purple is power, black is earth on the switch. Also check that the earth does earth.

On my car (pre facelift) the fuse for these lights is No 13 in the auxiliary fuse box, which is below the dash on the passenger side 9you may have to remove the knee/shin trim to get to it, maybe not, 10 amp fuse. Check this first? Note that one switch on the dash does the rear lights, and one the front lights, but ONLY the passenger map light is activated by the front switch, not the driver's side.
Greg

On the 90-91 conv. there is a relay like component called the "delay unit" which must have been what I was thinking about. It is located in the right component panel.

A word of caution the schematics for interior lighting are mislabeled in the Electrical Guide. The Coupe schematic is actually the Conv. one.

I've attached the schematics

Thank you for the schematic, I will ponder it.

Greg, thank you, yes, fuse. On this pre-facelift convertible, there is no centre light, but there are two in back. I need bulbs for those.

The diagram in the fusebox specified a 5 amp fuse, and it was blown. I did not have a five amp, but conveniently located in the panel cover was a 4 amp. Worth a try until I can get a five tomorrow, and better than the 15 and 30 spares next to it.

Popped it in, and both map lights and the puddle lights in the doors turned on. Good so far.

Got in, made sure the doors were closed. Delay circuit worked, after a pause, the lights went out. Now we are getting somewhere.

But.

Turned on switch #1 (left most switch). No light on the left, light on the right on.
Turned off switch #1, and turned on switch #2. I half expected either the left light to come on, or perhaps both lights. Instead, no lights with switch #2.

Open the doors, both lights and puddle lights on. Closed the doors, delay works. Went through the whole loop several times, same result.

Bottom line: Switch #1 lights the right light. No lights with switch #2.

Thoughts?

Read the last paragraph in Gregs post #7. The map light only works on the passenger side

Check the door switches.

Assuming new bulbs in the rear do the trick for switch #2, it's as Greg says, nothing wrong with your lights.
Other than LHD verses RHD mine do the same.

Yes, thank you. After viewing the diagrams, I now understand that what I was calling "switch #1" based on the "1" printed on the switch, is in fact the map light switch and not the interior light switch. I had thought it would be reversed, as the driver would want the switch closest to him light the interior, while the passenger would be more likely to want the map light to be close to him, but I see now that I was being unnecessarily logical.

New bulbs for the back are on the list for today. We shall see. I am at a loss as to why missing bulbs would shut the whole system, as that would mean they are in series and not parallel. Additionally, they are on rocker switches that may be off, off when the door is closed but on when open, or on, so if they were in "off" position the switch on the dash would never do anything, but I may be over-thinking it. Either way, I've learned something. The most important point: "First principles, Clarice..."

Have you dismantled or cleaned the switches yet? If not I would start there

So what we learned today is that the "interior light switch" works the back lights.

My drivers side switch is actually broken internally, which is why there was no bulb.

Passenger side had a bulb, but "something" was not right in the wiring. Difficult to explain, but the repair obviously went wrong.

Pulled the duct tape (yes, duct tape) on the PO repair, spliced and soldered in a new wire, end now it works as it should. I still think the map light switch should be closer to the passenger, but that's the way it is.

It is in other markets, after all it is an English car.