Clock to tach - swap in progress

[Onion]

My temp gauge went kaput so I went looking for options to fix it. I ended up purchasing an entire '85 cluster with tachometer - to replace the cluster on my '85 with clock.

Mostly the new cluster appears to be fully functional: except for the blinky temp light and the tach. The temp gauge appears to move correctly: I have researched the flashing temp light problem and found lots of material to try to troubleshoot that (coolant sender... relay #43... etc. for those who have been there.) Currently I am looking for ideas on what's next for the tach...

Based on previous posts/suggestions I was hopeful that the switch from an '85 clock to an '85 tach would simply be "plug and play." As it is, upon start the tach dial currently rolls up close to max/6k and just sort of floats there with some slight movement. I noticed that when hazard lights are on the tachometer jumps slightly in the same rhythm.

-Is my van really wired for a tach, even though it did not come with one?... and so perhaps this is some sort of relay/electrical issue?
-Or is the tach just moving to some other signal, and my van needs some kind of new wiring?
-Or something in-between; like switching wires/pins?

Also, in case it means something, I can see on the 14-pin clip in the van that there are no wires on the 4 or 12 pin (which I believe the Bentley identifies as correct for an '85.)

I am a total novice at working on autos, and it is a slow process for me to make any sense of this stuff. Thanks for any help offered.
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'85 Vanagon Adventurewagen

[bucko]

Your 85 is pre-wired for a tach. My guess is that your tach kaput, or that the "flexable" blue cluster wiring is bad.
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Current VW drives: 1984 Westfalia

Past VW drives: 1967 Beetle, 1973 Beetle, 1977 Bus, 1971 Military Type 181

[Onion]

Addtl info: When the ignition is on but the motor is not running, the tach wavers slightly around 3-4k. When the engine is running the tach wavers up around the top end. Yet the actual RPMs appear to have absolutely no effect on the movement of the Tach.

I checked the little three prong voltage regulator, and it seems to be in the 9.5-10.5 range.

I'm in for the night. Tomorrow I will try to solve the blinky coolant light, and work through any suggestions I can get on the tachometer... otherwise I am really at a loss for that. Thanks.

P.S. (at least the digital clock seems to work, so I will hopefully be no worse off if I can solve the blinky coolant light [and I now suspect that my blinky coolant light did not function AT ALL in the old cluster - I don't think I ever noticed before if it did or not...])
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'85 Vanagon Adventurewagen

[Witless Joe]

I'm betting that it's a problem in the part of the blue foil that actually plugs into the back of the tach.

There's a little rectangular plastic plug that holds 4 pins, although only 3 are active (12v, ground, tach signal). It snaps into the back of the tach.

Push that plug tight against the back of the tach the next time you're running the motor. See if pressure from your finger there changes the reading on the gauge.

I would get flaky readings like you when my connections were bad at that plug. Eventually it got so bad that I had to just bypass the blue foil altogether for the tach leads, and I soldered & wired the three pins directly from the tach to their various sources (12v, ground, tach signal). Ugly, but it works.

That blue foil is evil.

[wgargan]

what year began the pre wiring for the tach? I'm just wanting to know if my water cooled '83 is wired up. any way I can check if no one knows?

thanks
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Current ride:

1983.5 Watercooled Vanagon 'L' Automatic transmission

[crazyvwvanman]

The tach dash only has 1 extra wire added for the tach signal, running from the ignition coil neg side to the 14 pin edge connector of the instrument cluster.

All Vanagon clusters use a 14 pin edge connector. There are 2 basic layouts. 80-84 and 85-91. These have nearly every wire in a different spot from each other. To use an 85-91 cluster in a 80-84 means opening the connector housing and moving all the wires around to the right spots.

The 84 Wolfsburg models came with tachs and already have the wires in the locations for 85-91 clusters.

There are other wires that can vary by year/model on the 14 pin connector.

Mark

[MarkWard]

Search can be your friend. This is very helpful information. http://www.oldvolkshome.com/late_van_cluster_install.pdf
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☮️

[psych-illogical]

Generalizing about the 85-91 instrument clusters isn't exactly right. The 85 cluster is different from the 86. The tach is a different unit and the 86 and up cluster is also wired for the dyanmic oil pressure system (which I don't really understand). Let's try this:

Holy crap that worked!

Anyway msinabottle provided me with this pinout some time ago and it was immensly helpful. I had a weird floating tach needle problem and a constantly blinking temp light in my 83 1/2 Westy until I wired it like this. I also used the Bentley manual to help me decipher things. I found that using a tiny little jewelers screwdriver I was able to coax the metal connector out of each slot in the plastic 14-pin connector and move it to it's new location without having to cut and splice any wires. I think 9 should say G (green) wire from coil.

Good Luck
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83 1/2 Westy waterboxer
'57 Beetle-sold
Coupla '81 BMW motorcycles (R80G/S; R100RS)
'96 BMW R1100GS

[crazyvwvanman]

No need to coax each wire out with a jewelers screwdriver. The 14 pin connector housing flips open so the wires just slide out and back in where needed. Then close the hinged cover to lock them in.

There is no comprehensive list of instrument cluster wiring variations that has every difference for every year and model. Too complicated to do. Best to describe the fact that there are 2 basic layouts. If you plug a cluster from one layout into a 14 pin connector wired for the other, damage can result and nothing will work. As long as the basic type matches at least 90% will work and damage won't be an issue.

Mark

[msinabottle]

I bought a console that had a tach... and the quartz clock... Got to thinking... got them both to work, I found those pinouts on the old Westy mailing list and made that table once I'd successfully banished my own post-tach gremlins.

Yeah, that's almost certainly the best mod I've ever done. Watching the tach always gives you something to do when you're hunting for mileage. That little quartz clock keeps the best time of any vehicular clock I've ever had.

Best!
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'Winston,' '84 1.9 WBX Westy
Vanagon Poet Laureate: "I have suffered in
many ways, but never, never, never in silence."

[benandmj]

I'm bumping this back to life as the original question/ problem was never reported solved. Of all the 'clock to tach' posts here, this is the only one I've found that addresses an 85 clock cluster swap to an 85 tach cluster.

I was under the same impression as the OP that it would or should be a direct plug and play swap. I got my hands on a very clean 85 tach cluster and installed in place of my clock cluster and everything works but the tach. The needle doesn't budge. The green tach wire from the coil looks good in the engine bay and in the 14 pin connector. The blue foil looks great too.

What am I missing? Any ideas on how to test tach to see if it's bad?
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85 Westfalia Weekender
91 Syncro Westy

[crazyvwvanman]

How many green wires are going to your ignition coil?

Open up the engine compartment wiring box and look at the 2 round 7 pin wiring connectors. Does one of them have green wires going in and out of the same pin number?

Mark

[benandmj]

Just one green wire from the coil.

Goes in to this and not in to either 7 pin round connector

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85 Westfalia Weekender
91 Syncro Westy

[MarkWard]

This maybe unrelated, but there are two flavors of tachs out there. They look identical from the front. I thought the change was in 86, but the difference is that one tach is designed to see a signal from the earlier ignition system 84 and 85? The other tach is suited to the later ignition system. I know this from my own experience. I have a diesel, but could not get the 86 tach to work with my W terminal with the dakota digital interface or from the ECU. I did test it with an aftermarket tach to know that the wiring was proper and the dakota digital interface was working properly.

Don't recall, but a member either here or on the yahoo group suggested a tach from an earlier van. In fact, for a few dollars took my 86 tach in trade. It works now off the ECU and while not accuate across the entire range is accurate at my cruising rpm. I can't comment on the type of signal the two vanagons type tachs are expecting but it is slightly different. Good vanagon cluster info at Oldvolkshome website.
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[crazyvwvanman]

Well there is your problem. The single green wire is only for the ignition module. The tach vans have a second green wire from the coil, plugged into the other side of that white 2 pin plastic housing. The second wire leads to the 7 pin round connector in the engine wiring box. From there it goes with the main harness to the front. Does one of the round 7 pin housings at least have a green wire on one side? If so you can join that green wire to a new wire to the coil. If not, you will need to run a new wire from the coil to the dash.

Mark

[benandmj]

Yea I think the change is in 86. Wish I hadn't sold my known good tach when I got this cluster...
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85 Westfalia Weekender
91 Syncro Westy

[benandmj]

Mark, thanks for the info! In attempting to make sense of the Bentley diagram, I was wondering if that was the case! I'll run a wire and report back.

Edited with add question:
If I run the new wire to #9 then I can't help but wonder where the green wire that is currently in that location is coming from? There is one open spot on one side of one of the 7 pin round connectors but it doesn't appear to correspond with a green wire on the other side. I guess i will play it safe and run a new wire.
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85 Westfalia Weekender
91 Syncro Westy

[crazyvwvanman]

What color is the extra wire in the 7 pin and what are the colors of the wire on either side of it? You may be able to use it if it goes up to the dash.

Mark

[benandmj]

The extra wire is grey with a white line. It's between a red and black and a grey and black. Searching for them up front now.
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85 Westfalia Weekender
91 Syncro Westy

[benandmj]

Ran a new wire from the 2 pin plastic housing to #9 in the 14 pin connector. Turned the key in the van and got a spark/ pop from the battery and everything went dead. Turned the key and nothing. Disconnected the new wire and jiggled the battery connections and we are back in business. Stumped.

Edit: disregard. I now have a tach.
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85 Westfalia Weekender
91 Syncro Westy