Lights - rotary master switch

robdean · Post by **robdean** » Sun Nov 23, 2008 11:52 am

I'm inexperienced at reading vehicle circuit diagrams. I've tested the connections of the rotary lights switch in my 480 and would be grateful if y'all could advise me if the results are as they should be. There's one connection in particular I wonder might be shorted when it shouldn't be.

The 6 pins connect as follows:

OFF position:
A-15-58 are all connected
M-30 are connected
56 is isolated

MID position:
M-30-58 are all connected
Pins A, 15 and 56 are isolated

FULL position:
30-58 are connected
15-56 are connected
Pins A and M are isolated.

Is this as it should be? It's on pages 36-37 of the 1991 circuit diagram downloadable from this site.

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I'm still trying to track down my lack of dashboard backlighting. If I remove this switch unit the non-rheo backlighting works... not sure how I could try to trigger rheo backlighting while this switch is removed.

Thanks!

kitt · Post by **kitt** » Sat Dec 06, 2008 11:57 pm

whats non-rheo?

chriskay · Post by **chriskay** » Sun Dec 07, 2008 12:07 am

kitt wrote:whats non-rheo?

Refers to the rheostat under the steering wheel controlling the dash lighting brightness.

robdean · Post by **robdean** » Mon Dec 08, 2008 1:04 pm

Thanks, I was maybe a bit too brief in my explanation. The electronic info center feature means backlighting the 480 dash is essential in daylight if the info is to be readable. Of course it's double-essential at night, 'cos then even the speedo etc need lighting. My backlighting has stopped working and I'm stumped how to fix it before MOT time in a few weeks.

If I remove the main lights rotary switch, the 'daytime' illumination of the dash then works fine (the backlighting comes on with the ignition and has maximum brightness). At night (or rather when you turn the headlights on) the circuit is designed to add a dimmer (a 'rheostat') to the dash backlight circuit since 'daytime' backlighting would be too bright for night driving. This dimmer can be adjusted beneath the steering wheel. I can't get this circuit going so have no dash illumination when the headlights are on, though the headlights themselves work fine.

I wonder if a replacement main lights rotary switch will fix my problems, but am hoping someone might have some advice. As far as I can see, all the 'lights on' connections of my master rotary switch (the one which makes the lights pop up) are connecting OK, so I can't see how it will actually fix things - but I'm not confident of my interpretation of the pin-outs of the switch or of the circuitry,

I'd still really appreciate any advice. I'll be glad to buy a replacement switch from glasgowjim, but ideally I'd like to have some understanding of whether the one I have is faulty or not first, or whether there may be some other component I should seek instead. Especially since if a replacement switch doesn't work, I'm then REALLY stumped without some expert assistance. Those circuit diagrams mess my mind up, and I guess I'm not the only one as there have been so few responses to this thread! If you can't help, even a mark of sympathy or condolence would be appreciated...

All the best, y'all...

glasgowjim · Post by **glasgowjim** » Mon Dec 08, 2008 9:56 pm

just a thought check the rheostat (dimmer ) as it can screw the electrics up totally.

robdean · Post by **robdean** » Mon Dec 08, 2008 11:12 pm

Thanks for the suggestion, Jim, I'll take my meter to it...

...but having thought on it... surely a fault with the dimmer couldn't explain the problem with dash backlighting when the headlights are off as the rheostat is out of circuit then unless there is some other fault?

glasgowjim · Post by **glasgowjim** » Sat Dec 13, 2008 8:34 pm

the electrics on a 480 have never heard of ohms law hey are otally unfathomable.

beleive me t hey are as illogical as a woman

esta · Post by **esta** » Sat Dec 13, 2008 8:48 pm

glasgowjim wrote:
beleive me t hey are as illogical as a woman