Swapped clusters, instrument lights not working
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Senior User
Joined: May 2010
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From: Richmond, VA
Swapped clusters, instrument lights not working
I swapped clusters to a unit with a tach the other day, and only the far right hand bulb behind the gauges works. I checked the bulbs, and they seem fine. I looked at the circuit paper, and i don't see any obvious breaks, tears, etc. I swapped my old cluster back in, and the lights work fine. I'd really like to keep the whole new cluster, since it has a tach AND a trip odometer (which is good, since my fuel sending unit is shot). So, what should I check?
Moderator
Joined: Nov 2007
Posts: 22,415
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From: Denver Metro Area, CO
My guess would be the printed circuit itself. You can follow the circuit from where the
LB/R wire connects, my guess is there is a break in continuity *somewhere* on there.
An ohm meter is invaluable in this kind of diagnosis....
LB/R wire connects, my guess is there is a break in continuity *somewhere* on there.
An ohm meter is invaluable in this kind of diagnosis....
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
Light blue/red stripe, which is the circuit used for dash & instrumentation lighting.
To use your meter and test (I'm assuming the batteries are good and the unit is
functional):
Set your meter to *any* setting that measures resistance (ohms) and connect the test
leads to the appropriate locations (if necessary). If it's an analogue meter, the needle will
be in the leftmost position; if it's digital, it will read 1. This means there is no continuity
between the two test leads being detected at the time
Now, connect the two test leads to each other... if analogue, the needle will swing all the
way to the right; if digital, it will read 0. This means current is flowing through the tested
circuit with no resistance (in this case, the circuit being tested is that formed by the two
test leads connected to each other) and it is detecting full continuity.
To test your cluster... remove it from the vehicle, locate the lead on the printed circuit
where the LB/R wire connects. Place one test lead on the printed circuit at that location,
place the other test lead on different points along that same trace (circuit) until you find
the break in continuity.
To use your meter and test (I'm assuming the batteries are good and the unit is
functional):
Set your meter to *any* setting that measures resistance (ohms) and connect the test
leads to the appropriate locations (if necessary). If it's an analogue meter, the needle will
be in the leftmost position; if it's digital, it will read 1. This means there is no continuity
between the two test leads being detected at the time
Now, connect the two test leads to each other... if analogue, the needle will swing all the
way to the right; if digital, it will read 0. This means current is flowing through the tested
circuit with no resistance (in this case, the circuit being tested is that formed by the two
test leads connected to each other) and it is detecting full continuity.
To test your cluster... remove it from the vehicle, locate the lead on the printed circuit
where the LB/R wire connects. Place one test lead on the printed circuit at that location,
place the other test lead on different points along that same trace (circuit) until you find
the break in continuity.
Thread Starter
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Senior User
Joined: May 2010
Posts: 302
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From: Richmond, VA
Ok, so I pulled all the bulbs, cleaned up the contacts, checked the continuity and it all looked good. I put it back in, and this time, the only bulb that worked was over by the speedo. Out of curiosity, I moved that bulb, and sure enough, just that one bulb lit up. So, I swapped in a bulb from my old cluster, and that one worked too. So, even though all the bulbs looked fine, I swapped in all the bulbs from my own cluster, and bingo, all the bulbs lit up fine. Odd, but I'm happy 
