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Cluster lights/temp gauge (740)

M

moustacio

New member
Joined
Mar 10, 2012
Location
Colorado
Hi everyone,

A few questions about my 1988 745 with yazaki instrument cluster.

1) the background lights, illuminating the gauges, only work on the right side of the cluster. All of the bulbs light up when removed, so the bulbs are not the issue. Any ideas of where to start?

2) it would be nice to not have a compensated temperature gauge but I have yet to find a write up for my specific gauge. I looked at this thread:
http://forums.turbobricks.com/showthread.php?t=259116
but my gauge is different. Any ideas here? In the above thread he removes a diode and wondering if I can do something similar.

Thanks much for any information
 
Re-flowed some solder on the board and installed but still no background lights on the left portion. Smacked the dashboard and it lit right up.
 
My AC controller is the same way - gotta slap it for the lights to work. You’ll need some dielectric grease or contact cleaner to clean up the contacts; they’re just not making a good connection is all.
 
That at least is my problem. If the bulbs are like mine they should have tiny little wires smushed up next to the glass of the bulb - wrapped up against it. You could pull the wire out just ever so slightly so it’ll be snugger against the contacts of the cluster.

I’m not sure - someone may have to correct me - but if one bulb isn’t working, the others won’t either as they are all in line (again could be wrong). So if I’m right, once you fix the one the rest will work fine.
 
Yes, I couldn't find a diagram so I chased the path to the bulbs. And like you say they all run in line.

My bulbs have a socket with brass? contacts connecting to the board. The board looked scraped up where the bulbs twist in and I was thinking of using tin foil or something to ensure a better contact. Maybe flow some solder over the copper board where its scratched up. Does this thinking sound sound?
 
Again - might want to get verification from the other guys here, but tinning the contacts with solder sounds like a reasonable course of action :) Volvo used some really thin layers of metal and plastic for their cluster PCBs... I’d just be careful not to melt the plastic or scorch the traces. But adding fresh solder should work! Do you have any contact cleaner to run in there first? I use Deoxit D5 squirted onto a cotton swab, works wonders for car electronics and game boys :p
 
Hi stiligFox and thank you for the help.

I have some CRC electrical cleaner that I will try (I should get some of the good stuff though).

Probably won't get to it in a while but I will post back with any information.

Thanks again
 
Yeah maybe try retensioning the pins on the bulbs. It may be tricky, but one could test for voltage too.
 
stiligFox said:
I?m not sure - someone may have to correct me - but if one bulb isn?t working, the others won?t either as they are all in line (again could be wrong).
Click to expand...

moustacio said:
Yes, I couldn't find a diagram so I chased the path to the bulbs. And like you say they all run in line.
Click to expand...
Only a week late, but no, they are not "in line" (series) like old Christmas light strings. They are in parallel; common voltage on one side of all bulbs, common ground on the other side. As a safety issue, you can't have the entire dash go dark just because one bulb out of 30 goes bad.


Series: ............................................... Parallel:

_3229073_orig.gif
 
MasterBlaster: thanks for the clarification.

ZVOLV: thanks for another idea on how to address the issue.

I'll let y'all know how it turns out. I'll probably try all suggestions at once while I have the cluster out again.

Thanks again everyone
 
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