TheSamba.com :: View topic - wiring issues with instrument panel lights and VDO gauges

Sat Jun 25, 2011 10:27 am

Yesterday I finished connecting my 3 VDO gauges I mounted under the radio (thanks to a very helpful drilling template from Scott Lyons!!) and all was well until I started using my dimmer on the headlight switch, at least I think that was where it started, and now I have no lights on the dash except for warning lights. The lights were fine when I first tested them except for one of the VDO gauges and at the time I thought I would just change it later, before final installation.

So my investigation process began and went something like this:

1) checked all fuses in fuse box - OK

2) checked headlight switch to see if spring had busted (I recently got a used switch from Scott L cuz my OG "unsprung" - crispy sounds!!) - spring still there and looked in good shape though I noticed the switch contacts on the rotating body that holds the resister seemed to be loose and the switch seemed to "over rotate" compared to other spare switches I have (broken springs too!!). I am wondering if I turned it too much when putting the knob on or off cuz it wasn't like that before

3) removed bulb holders on VDO new gauges and the oil press. gauge bulb was blown and it was obvious cuz the bulb was cloudy white and it was really hard to get the holder out of the gauge, as if the holder had grown bigger!! So I assumed once I got the holder out and noticed the white bulb that it had gotten hot. I had to beat up the bulb holder to get the bulb out but figured I was going to need a new bulb holder anyway

4) double checked my wiring job to make sure power was power and ground was ground. This is one place where I am less that confident because of the lack of + and - indicators on the bulb holders so I do not know if it matters which pole I use for power and which for ground on the bulb holder. I wired them using the "daisy chain" method on the existing lights, which I assume is parallel, though I am rusty on my network theory. One thing about the wiring is that I did not ground them all to the same place AND I also have a VDO tach in place of the clock that I put in last year, and believe the lights on that were all working last year.

5) now suspicious about the switch I was thinking of taking my test light or voltmeter and seeing if there is power at the terminal on the switch where the dash light wire is connected and go from there but I am not sure what to do after that and since the one bulb was really cooked I am now uncertain about my wiring and wonder if I need to sort that out first before blowing another bulb or 2

Any ideas?

While I wait for a reply I may go and test that switch terminal.

Thanks

Sat Jun 25, 2011 11:09 am

Even if the rheostat in the switch is cooked the lights will still come on full bright by turning it all the way to the right (or left, can't recall), it's also impossible to screw up a switch installing the knob unless you actually twist the shaft off. As for the bulbs the highest voltage available anywhere under the dash is battery power (12V), unless they were 6V bulbs the issue is with the bulbs themselves, not the wiring.

Sounds to me like you've pulled a wire off a terminal on the headlight switch.

Sat Jun 25, 2011 11:28 am

Thanks Busdaddy. Yes I knew about the rheostat and full brightness with it being broken from all the threads I have read today. So I just double checked that the wire is connected to the terminal and it is fine.

Voltmeter test results;

HL switch off:

Terminal 30 - 12 V
lights terminal - 0 V

HL switch on:

#30 - 12 V
lights terminal - 0V in both max L & R positions and hear an audible click at full R position but still no voltage and also tested with knob turned at about 3 random rotation spots

My conclusion is that the switch is pooched at that terminal.

If I were more certain about the wiring I would try one of my spare switches to see if I can at least get the lights on full brightness but I am a bit reluctant about connecting another switch and having the same thing happen if my wiring is wrong. Maybe if I take a photo of my set up someone could comment on its integrity. I will try that now and figure out how to post it on my next reply.

Thanks,

By the way, this is a 74 Westy. I don't know how to add a "signature" with my vehicle details on my posts like i see others do but I will check the FAQ on that.

Thanks

Sat Jun 25, 2011 12:26 pm

[quote=

By the way, this is a 74 Westy. I don't know how to add a "signature" with my vehicle details on my posts like i see others do but I will check the FAQ on that.

Thanks[/quote]

Log into the control panel. There is a section (box) for you to add your
signature. :)

Sat Jun 25, 2011 12:31 pm

test for signature

Sat Jun 25, 2011 12:40 pm

so now my signature works but my photos are over 600KB so I need to shrink them before I post. Once I figure it out I will post photos. Also, it was the CHT gauge not the oil press. gauge with the light burnt.

Sat Jun 25, 2011 1:20 pm

So here we go with the photo attempt.

FYI - I used white wire for power and black for ground as I did not have any red or brown that I could find at the time.

The empty light socket is the CHT and since I don't have a replacement bulb and holder for it at the moment I am going to have to tape the ends of the wires if I install before I get one. Also my oil press. gauge is not working yet because the adapter hose I bought from ACN leaks oil and I am waiting for a reply from them about what I did wrong, so the main power and ground wires for the gauge itself are already taped (middle gauge)

Sorry for the poor quality of my iphone camera

Thanks in advance for any comments on whether this wiring for the gauge lights looks ok.