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Instrument light troubleshooting
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Tom Powell
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PostPosted: Mon May 25, 2015 6:39 pm    Post subject: Instrument light troubleshooting Reply with quote

I've done a search of the 347 posts on inoperative instrument lights and researched the Bentley and the Haynes. I'm starting to troubleshoot and find the reason my three instrument light and the blue high beam indicator light do not work in my '87 Vanagon. I'm trying to keep it as simple and unfrustrating as possible This post is to memorialize the trouble shooting procedures and solicit help/corrections from those more knowledgeable than I. I'm trying to do the easy and logical things first.

I pulled and checked the bulbs. They were all good.

From the Haynes I learned that there is a "hidden" 10 amp fuse for the instrument lighting above the main fusebox. I pulled that fuse to check if it was good. Unfortunately, with my fat fingers I flipped it somewhere and pulled the fuse block looking for it. Finally found it in the steering shaft cover, checked that the fuse was good and then reinstalled the fuse, fuse block, and cover. I did not check for power to the fuse, but will be doing that soon.

I then checked the rheostat and found that the lights for the climate control levers were functioning and the brightness was adjustable. From this I assume that there is power to the fuse, it is available to at least the rheostat, and the rheostat is working as intended.

From other posts and what I can understand from the Bentley diagrams I will next be checking the 14 pin connector. From the diagrams I believe that 14/1 is the power for the instrument lights and 14/3 is the ground for the instrument lights.

The 14 pin connector has been exercised several times as I replaced my clock instrument cluster with an '87 tachometer cluster. I assume the exercise would have have resulted in good contact, but my next step will be to clean the 14 pin connector with DeoxIT, insure that the pins are clean and straight, and the wires making good contact in the connectors.

I'm waiting for an Amazon delivery of the DeoxIT and will update after the cleaning. If the cleaning does not resolve the problem I think that checking the 14 pin connector for ground and the foil for breaks and power will be next. It appears that it is highly likely a grounding issue, possibly 14/3.

Several posts I've read mention the gray/blue tracer wire and I'll need to review those posts and the Bentley to understand the function of that wire.

The final solution might be a jumper wire to the instrument light bulbs, but that wouldn't do anything for the high beam bulb.

Aloha
tp
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Tom Powell
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PostPosted: Wed Jun 03, 2015 9:38 pm    Post subject: Reply with quote

The DeoxIT arrived from Amazon. I used it to clean the 14 pin connection and the other connections at the instrument panel. I checked the bulbs themselves and they were all good. The instrument lights and high beam indicator still do not work, but the climate control lights do work. The next step will be to check 14/1 for power and 14/3 for ground and the grey-blue wire.

Any advice or comments on how to continue the troubleshooting?

Aloha
tp
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Phaedrus
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PostPosted: Wed Jun 03, 2015 10:21 pm    Post subject: Reply with quote

Check for power and ground to the T-connector as you're about to do. If it doesn't check out use the Bentley diagram to figure out where the wire originates and keep checking for continuity until you find the break.

If power/ground are fine, check your foil on the back of the instrument cluster. This is the second weakest link (first being the LED bulbs). Check for continuity starting at where the T connector meets the printed circuit board to where the LEDs seat into the board. Even with continuity, there can be small tears in the printed circuit board than will cause shorting. If you find that you don't have continuity somewhere, there's your problem. Find the tear and solder it carefulllyyyyy. Be extremely careful when handling the printed circuit board. It's probably the most fragile oem part on the van...

Something's not right somewhere in the circuit. The trick is narrowing down exactly where it's gone awry. Hope this helps
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Tom Powell
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PostPosted: Thu Jun 04, 2015 9:36 am    Post subject: Reply with quote

Phaedrus wrote:
... Hope this helps


Thanks for the reply to my posts. It didn't actually help, but does reaffirm what I need to do. That in itself is a help.

I would like confirmation that 14/1 is the power source for the instrument lights and that 14/3 is the ground. I do not yet understand how power from the light switch gets to the 14 pin connector and then to the instrument lights. I'll be digging into the Bentley after this post. Then digging in and tracing the wiring in the vehicle.

After cleaning the connections it seems that most likely the problem is in the foil. Finding a break in the foil and repairing it will be a challenge. If I find a break I will use "Conductive Wire Glue" from Radio Shack instead of soldering. I'm replacing an instrument cluster that was hacked with soldering. I bought and used the CWG to repair a test light and so far it has been an excellent product.

Do you have any input on the grey wire with blue tracer and it's function in the wiring? I struggle to read and make sense of the newer Bentley wiring diagrams. They are not as intuitive as the older diagrams.

Aloha
tp
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B-bear604
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PostPosted: Thu Jun 04, 2015 10:59 am    Post subject: Reply with quote

If I remember correctly from my dash lighting issue the grey with the blue tracer is for the dash lighting that is independant of the foil. you know switches cig lighter, the lighting for the fan controls for front and back heaters. You should see it on your rear defroster switch.

I know when I had this issue it was in the main connector to the foil with the ground connection and some corrosion there. as for which connection is the ground in that connector easest way is look for the brown wire and which connector is it in.
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Tom Powell
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PostPosted: Thu Jun 04, 2015 11:34 am    Post subject: Reply with quote

B-bear604 wrote:
If I remember correctly from my dash lighting issue the grey with the blue tracer is for the dash lighting that is independant of the foil. you know switches cig lighter, the lighting for the fan controls for front and back heaters. You should see it on your rear defroster switch.

I know when I had this issue it was in the main connector to the foil with the ground connection and some corrosion there. as for which connection is the ground in that connector easest way is look for the brown wire and which connector is it in.


That all makes sense. I've been looking at the 14 pin connector in the Bentley diagrams 97.108 and 97.109. I see that 14/1 is the power source, but i cannot find 14/3 or 14/4 on the diagram. I will now assume that 14/3 is the ground "s" for the instrument lights and that "r" is 14/4, a ground for other cluster items such as the tachometer. "s" is is also the ground for the high beam light. The instrument lights and high beam light are all inoperative and the smoking gun is 14/3 "s".

B-bear604 wrote:
... as for which connection is the ground in that connector easest way is look for the brown wire and which connector is it in.


DUH Why didn't I think of that? Rolling Eyes

I'm going out to the vehicle to check 14/3 for ground.

Aloha
tp
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Tom Powell
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PostPosted: Thu Jun 04, 2015 1:08 pm    Post subject: Reply with quote

Did some testing with the dash cluster out:

14/4 is unused
14/3 is a good ground at the female connector
14/1 did not have power in any ignition switch position
connected the headlight switch and 14/1 had a dim light using a circuit tester
moved the rheostat wheel and the light got brighter and dimmer

For information only:
Lying under the dash cluster there is a connector with a brown wire and a white wire with blue tracer. The ground is good and the white/blue wire has no power in any light or ignition switch position.

Conclusion at this point:
Everything is good up to the light switch and 14 pin connector.
The VW engineers threw in an extra connection to confound and confuse us DIYers
There is a problem in the foil.

Next step will be on the bench to inspect and clean the male connection at 14/1 then to put some power to it and probe the foil with a test light. I'll first do some practice powering and probing on the hacked foil that I'm replacing.

I may postpone the powering and probing. I have a parts Vanagon in Hawaii. Cutting the 14 pin female from that and using it for the bench work when I return to SoCal would make the job easier.

Aloha
tp
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wcdennis
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PostPosted: Thu Jun 04, 2015 3:38 pm    Post subject: Reply with quote

I have a bunch of wires with alligator clips on either end that are real useful for tracking down this sort of problem. I would try connecting 12v to the foil terminals 1 and 3 and see if the dash lights glow. If so, you know the foil traces are good and the bulbs are making contact.
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PostPosted: Thu Jun 04, 2015 5:05 pm    Post subject: Reply with quote

wcdennis wrote:
I have a bunch of wires with alligator clips on either end that are real useful for tracking down this sort of problem. I would try connecting 12v to the foil terminals 1 and 3 and see if the dash lights glow. If so, you know the foil traces are good and the bulbs are making contact.


I decided to continue the work, partially because it has become personal challenge. I tried the hacked foil first using a ohmmeter and checked continuity from 14/1 (power) to each side of the foil at the bulb. Did the same for 14/3 (ground). All was good, got continuity when expected, and no continuity when expected. Did the same for the foil in the replacement cluster. All was good there also.

I put bulbs in the hacked foil and using a spare battery, put 12V+ on 14/1 and the ground on 14/3. The bulbs lit up as expected Did the same with the replacement cluster foil, but no lights. WTF. I used the DeoxIT on the foil at the bulb connections and retested. Still no lights. Tested all four bulbs. All good. WTFA How can something pass all the continuity checks but not work when power is applied? Perhaps my alligator clips and jumper wire technique when battery testing the replacement foil was lacking sophistication, but it worked on the hacked foil. All the continuity tests were good from 14 to bulb sockets, but the lights didn't work with power applied.

Just opened the first beer at 1630 and will reinstall the cluster later and check the lights tonight. Haven't reached the FI stage yet, but I can get by with a penlight to check the fuel gauge at night when driving.

Aloha
tp
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wcdennis
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PostPosted: Thu Jun 04, 2015 5:50 pm    Post subject: Reply with quote

Are the two clusters from the same year? There are at least 3 cluster variations, and I'm pretty sure the dash light connections are one of the things that changed.
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Tom Powell
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PostPosted: Thu Jun 04, 2015 6:14 pm    Post subject: Reply with quote

wcdennis wrote:
Are the two clusters from the same year? There are at least 3 cluster variations, and I'm pretty sure the dash light connections are one of the things that changed.


Both of the clusters and foil came out of '87 Vanagons, however I cannot be certain that the hacked foil was OG to the Oregon/SoCal '87 Vanagon. The replacement cluster, with a tachometer, is from a manual transmission in Hawaii that had an engine fire. The hacked cluster is from an automatic transmission, from Oregon now in SoCal, with a clock. The intent was to get a tachometer into the drivable vehicle and I found the hacked cluster during the "upgrade". Apparently the hack was to disable the oil pressure warning because that was easier than to replace the sensor on the engine.

I do have that mystery white/blue wired connector that was hanging below the cluster, but I couldn't find any combination of light switch and ignition switch that gave it power, nor do either of the clusters have a mating connector.

Aloha
tp
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Tom Powell
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PostPosted: Thu Jun 04, 2015 7:18 pm    Post subject: Reply with quote

Minor success. I reinstalled the cluster and the light on the tachometer worked, but very dim, I assume that cleaning the foil contacts at the bulbs resolved the problem and that another cleaning might make the other bulbs work and the working bulbs a bit brighter. No need now to use a flashlight for the fuel gauge. I can see temperature, fuel quantity and RPM now and they're more important to me than MPH.

I'll check out the other lights when it gets dark.

Next bit of search will be about LED's.

Thanks for all the replies.
I'm not done yet.

Aloha
tp
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Tom Powell
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PostPosted: Mon Jun 15, 2015 5:23 am    Post subject: Reply with quote

Upate:

Got the instrument panel swapped and the instrument lights working.

Used deoxit and model airplane cotton swabs on the foil at the bulb contact points and put a few scratches in with a pick. Finished with the deoxit gold. One bulb burned out during the many R&R's resulting in a mystery when it was used. Used a spare 12V battery for bulb testing, but was never able to get the bulbs in the foil working on the bench using the 14 pin connector. Unused clock and hacked foil parted forward. MX on last mainland trip: oil pressure sensor and Instrument cluster swap.

Aloha
tp
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Wasted youth
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PostPosted: Thu Aug 13, 2015 11:26 pm    Post subject: Reply with quote

Thanks for doing this. You are probably saving me a lot of time and irritation, as I have the same problem with instrument lights only, and the Hi-Beam LED... which is actually on at the right time, but dim.

Note that I also have to hold the stalk back to get the hi beams to work, but that is a different thread.
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