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Diesel Tach availability problem - Solved
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BlackDogVan
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PostPosted: Mon Dec 20, 2010 3:50 pm    Post subject: Diesel Tach availability problem - Solved Reply with quote

So I think I've got a fix for the un-obtanium vanagon diesel tach for pretty cheap but some assembly required. I'm sorry I wasn't planning a post on the subject so I didn't take any pictures. Everything is stolen from the internet.

This is what we all want to find:

Image may have been reduced in size. Click image to view fullscreen.


I believe this is known as the CE1 wiring tach with temp & fuel gauge.

But with the exception of the ultra rare Qauntum TD tach or a mega money tach from a euro T3 its impossible. I did manage to find a few Quantum TD tach's & have one installed & working. It did take a complete disassembly of the clusters, not for the feint of heart, but its pretty simple to do if you're careful.

Anyway... from taking apart a few tachometers it would appear to me that all the mid 80's tach's share the same connector, shape, mounting position with the exception of the two very small black screws that hold the face. The diesel's (on my quantum tach) are closer together than the stock vanagon tach. These pictures show that some are in the same place.

Image may have been reduced in size. Click image to view fullscreen.


So anyway from my experiences taking apart Vanagon clusters here's what I propose as the solution to the tach shortage.

Go online & find a used CE2 diesel tach like this one:
Image may have been reduced in size. Click image to view fullscreen.


I don't believe they are that rare as they were in the majority of the Mk2 diesel Jetta & Golf models from 86-91?

Disassemble it complely (I found a dinner fork works best for removing the pointer) and install the diesel tach module in the place of your existing vanagon unit using the vanagon back / mounting plate. Actually before you install it break the brittle glue (very careful here) that holds the tach speed adjustment potentiometer from losing its cal on the back of the tach module. I used an exacto knife & it was easy to do. Mark where that pot is on the inside of back / mounting plate and drill a small hole in the back plate so you can stick a jewlers flat head screwdriver in to make adjustments later. I'd start with a 3/4 turn clockwise here BTW. Clockwise lowers the tach rpm, counter clockwise raises the tach rpm. Time will tell if vibrations can cause it to rotate & need another cal. The stock calibration read approx 2x high.

**note here, I had to make adjustments because I have a serpentine setup on my engine. The alternator has a smaller diameter clutched pulley which causes the tach to read high. If you still have a v belt alternator you might not need to bother here.**


Now to make it look like a stock tach. Drill the mounting face screw holes if they are different to match how your tach face is secured in the cluster. Some models screw into the actual tach module & others go into bosses on the plastic back/mount plate. Don't worry about messing it up, you could scratch your name in the tach face if you want, it won't matter. Again you might not need to worry about this step as you're reusing your back plate & tach face anyway.

Now email this guy (or do it in advance of taking your cluster apart Wink ) & ask him to reproduce the stock CE2 tach face for you. I got him to make me a custom one years ago & it turned out very nice. I just wish I could find it now...

http://www.thesamba.com/vw/classifieds/detail.php?id=602331

So I think you can see where this is going now. Once you glue the new face to your old gas tach face & assemble it all back you can have a stock appearing diesel tach for a fraction of the cost of the other options.


In the process of installing my 2.02 Quantum tach I thought I killed it by keeping my Dakota Digital box inline to adjust it easier. (you can't & it didn't kill it) Thinking it was dead I installed a 2.22 MK2 jetta tach & it worked as well, it just read a bit higher so I know the alternate diesel tach body will accept the w terminal signal through the stock vanagon cluster wiring. One thing I can't vouch for is that the 2.22's pot has the same range as the 2.02 Quantum tach i'm using. My gut says it will though.

As for performance of the Quantum unit, its accurate now that i've calibrated it. I do find it hangs ever so slightly when engine RPM's are decreasing very slowly. I chose to concentrate on getting the RPM bang on at 3000rpm not idle using a GPS & the final drive ratio's.

Regarding monkeying around inside your cluster, you really can't be to careful with the ribbon circuits. I'm currently trying to find out why my oil pressure LED doesn't want to blink alarms at me anymore. It just wink's once when I first turn on the ignition. (help please!!)

Anyway, hope this helps out some of the diesel converts out there. Some might wonder why I bothered since I had one of the rare gasser tach's that worked with the Dakota box. I'd tend to agree.

PS I have a 1575 Syncro speedo from a quantum if anyone with larger tires on their syncro wants an accurate speedo. Looks like it'll fit & appear stock with just a bit of tweaking. (pm)
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I am Wildcat
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PostPosted: Thu Mar 03, 2011 8:33 am    Post subject: Reply with quote

Great write up, that setup looks awesome!
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rotaecho
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PostPosted: Fri Jul 07, 2017 8:33 pm    Post subject: Re: Diesel Tach availability problem - Solved Reply with quote

I just did this with my mTDI, but I'm still struggling here.

The cluster has the MK2 CE1 tachometer

I ended up doing a serpentine setup using an ABF alternator (AL0187X) which I *thought* based on my research had a W signal, but some are saying it's an ECU signal not W signal which would explain the tachometer erratic behavior.

I'm trying to figure a route to get this combo to work and open to any insights here.

If I painted myself in a corner, what would be the least path of resistance to get it working?

Thanks!
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?Waldo?
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PostPosted: Fri Jul 07, 2017 8:55 pm    Post subject: Re: Diesel Tach availability problem - Solved Reply with quote

The W-signal is not anything esoteric. The alt will not generate anything other than W or DC output. Does the plug on the alt say "W"? Most of them do. If not, then you can solder a wire to one of the connections prior to the rectifying diodes. There were quite a few online tutorials on it last time I checked.
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Zeitgeist 13
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PostPosted: Fri Jul 07, 2017 9:48 pm    Post subject: Re: Diesel Tach availability problem - Solved Reply with quote

I soldered a wire on to emulate the W-signal for my ALH build. I'm currently in the process of modifying the stock gasser tach as found in this thread:

https://www.thesamba.com/vw/forum/viewtopic.php?t=610274&highlight=gnarlodious+tach
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rotaecho
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PostPosted: Sat Jul 08, 2017 9:59 am    Post subject: Re: Diesel Tach availability problem - Solved Reply with quote

So my alt plug had a W stamped, and it did work briefly, but stopped. I checked plug and found a loose connector so crimped it more.

Tacho now working! (=

Thanks!
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?Waldo?
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PostPosted: Sat Jul 08, 2017 1:17 pm    Post subject: Re: Diesel Tach availability problem - Solved Reply with quote

Glad to hear it's working. Just an FYI, the W-signal will vary based on alt/crank pulley ratios. The TDI alts have a smaller diameter pulley than the earlier alts and so read higher than actual unless the tach is calibrated by some accurate method reading directly off the crank.
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PostPosted: Sat Jul 08, 2017 4:17 pm    Post subject: Re: Diesel Tach availability problem - Solved Reply with quote

Cool, Karl mentioned an optical tach to get a gauge off the timing belt crank I believe it was. I plan on using that when the temperature isn't a hundred and hell here.

Andrew A. Libby wrote:
Glad to hear it's working. Just an FYI, the W-signal will vary based on alt/crank pulley ratios. The TDI alts have a smaller diameter pulley than the earlier alts and so read higher than actual unless the tach is calibrated by some accurate method reading directly off the crank.

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Gnarlodious Premium Member
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PostPosted: Sat Jul 08, 2017 4:45 pm    Post subject: Re: Diesel Tach availability problem - Solved Reply with quote

Andrew A. Libby wrote:
FYI, the W-signal will vary based on alt/crank pulley ratios. The TDI alts have a smaller diameter pulley than the earlier alts and so read higher than actual unless the tach is calibrated by some accurate method reading directly off the crank.
True. When I put the Jetta alternator in my tach was way off. I had to adjust it with the tiny screwdriver in the back. I used the iPhone app to get the revs.
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