Help with swap of 1982 Cabriolet cluster tachometer

Regarding my 1981 Rabbit pickup, diesel, recently bought an instrument cluster from a 1982 Cabriolet (MK1) gas version with tachometer ... the 1981's did not have the tach, from what I've gathered so far.

In comparing clusters, the gas-tach one looks almost identical to the original one from my diesel pickup, except for a couple of items related to the circuit board.

1. Tach cluster has 3 wires coming out from within the 'box' adjacent to the speedometer, which 'appear' to have something to do with the speedo, and are screwed into the circuit board at that point. Colors are red, white and blue.

2. The majority of … what I will refer to as 'pins' on the tach circuit board … are the same in most instances, with only a couple of pins not being present. This circuit board is much closer to original than other diesel versions I have ... by far … with one presently installed, and seem to be functioning A-OK.
I 'think' the extra pins on my original circuit board, may have been for the a/c that was in the pickup; whereas am 'presuming' the Cabriolet did not have a/c.

3. Original board from pickup had clock, and was connected with 2 'prongs' of the board that went upward and attached to clock by screws.
Board of Cabriolet, with tach in lieu of clock, has these 2 'prongs' cut ... or they appear to have been cut ... since I see no screw holes for attachment.

Nor do I see any plug, spade, etc. for connection on the back of the tach.

Sorry about all the jibberish, but felt you need to know the background before my questions.

Does anyone have experience with this process of taking a VW rabbit, etc. version of tach and installing it into the diesel. OH ... by the way; I do have the proper alternator with the'W' terminal, and will be installing it.

Not seeing any difference in gas vs diesel version of circuit board, is there something else I need to know or be aware of? In other words, will it be accepted without frying my wiring or the tach or other items in the dash cluster.

How is the tachometer connected to the electrical system? As mentioned, tach displays no terminal or plug in the rear.
Any ideas what the 3-wires I mentioned are for?

I do have wiring schematics of the 81 gas and diesel, but not of the 82 versions. Does anyone have them that they are willing to share? Don't really desire to have to buy the 1982 Bentley, just for this one usage. If need be, I can scan mine and send along to compare.

Would appreciate any and all responses to this. Would like to get started swapping the clock from my original cluster over with the tachometer. When all's said and done, will have some extra cluster parts no doubt.

Thanks !!!

I have a tach in each of my 81 diesels and so does my brother. My brother has a sensor rapped around the alternator and he adjusted the gauge (autometer) to match correctly. The other options is you need a alternator with a "W" terminal (it is a separate spade plug on the alternator). It says on the alternator W or it is a B+. B+ won't work. The "W" terminal gives of a signal every revolution. The newer rabbits had the upshift light and I think they ran off this. That is about the only difference in the wiring as well. As for the circuit differences you won't have the glow plug light in the gasser circuit. To hook the tach up you have to run a wire from the alternator's W terminal and then you also have to be REALLY good at swapping resistors and capacitors out on the circuit of the tach itself. Yes you do have to take it apart. You have to un solder and re solder the circuit up to read the correct hits per rev. On a gasser it runs of the ignition system. Since there isn't any electrical things making the diesel fire and the alternator doesn't spin the exact revolutions as the crank you have to mod the tach. The crank pulley is different sized then the alternator. There is also a method that you can use a sensor that is run off a pulley.
http://www.4crawler.com/Diesel/CheapTricks/Tachometer/index.shtml
The tachs I have in aren't the most accurate but they work. The car goes down in rpm as the car warms up and the truck is different with and without the lights on. I played with it a lot and basically what my electrical engineering teacher had told me is that if the solder isn't perfect then that can change in resistance with the different temps. Hope that helps you. Let me know if I can answer any other questions on that. Finding an alternator can be a challenge with the W terminal. Also you can move the gauges to work with the original circuit. You do have to cut on piece off from the clock but the fuel and temp gauges still work in the different positions.

You really need to get a cluster from a 1.6 liter IDI turbo diesel. The TDs had a tachometer in place of the big clock. Check e-Bay (these are getting very scarce). The tachometer has the proper RPM range (redline at about 4500), and the low oilpressure warning circuit in the cluster is different from a gasser cluster (I found out the hard way with my '85 Jetta TD). Like mentioned above, you need an alternator with the "W" terminal, but may have one, because the "W" terminal provided a RPM signal for both the upshift indicator and the dynamic low oil pressure warning system on the diesel VWs.

FYI, I think in 1986 the diesel cluster for the turbo diesel went to a two connector model whereas before it used a bigger, one-connector plug, or vice versa, so you may need a cluster from '85 and before.

Here is a picture of the guage cluster of the '85 Jetta turbo diesel I once owned.



--Nate

Tach swap

You must have missed points of my post. I already have the 'W' alternator to install. Secondly, I am not planning on using the gas cluster, but to replace the clock in one of my other diesel clusters with the tach from the Cabriolet-MK1-Rabbit-etc. gas cluster.

Since the circuit boards appear to reflect minor differences, am wondering which version I should use ... the original one from my truck, or the one that came with the tachometer cluster.

And finally, how is the tachometer of any rabbit connected to the electrical system? The tach in the Cabriolet cluster shows several screws, none which are marked one way or another, and the 2 circuit board leads (used for clock) are broken or cut off.

In other words, if I run a wire from the 'W' terminal from the alternator, where would it be attached to read the tach output ... or are the 2 normal leads used somehow?

And if the 'W' wire goes to another junction point in the electrical system, how then is the tach incorporated?

Images of rear of tachometer (Cabriolet) instrument cluster.
1. Shows one of the leads that has broken off, or was cut. The other one is on the other side but not visible in this view ...
http://pics.tdiclub.com/data/4684/Cluster_3.jpg

2. Then, are the 3 wires in the upper corner (white, blue and red), that comes from where the speedo is ... for the speedo ... or something else???
http://pics.tdiclub.com/data/4684/Cluster_4.jpg

doon

coalminer16 said:

I have a tach in each of my 81 diesels and so does my brother. My brother has a sensor rapped around the alternator and he adjusted the gauge (autometer) to match correctly. The other options is you need a alternator with a "W" terminal (it is a separate spade plug on the alternator). It says on the alternator W or it is a B+. B+ won't work. The "W" terminal gives of a signal every revolution. The newer rabbits had the upshift light and I think they ran off this. That is about the only difference in the wiring as well. As for the circuit differences you won't have the glow plug light in the gasser circuit. To hook the tach up you have to run a wire from the alternator's W terminal and then you also have to be REALLY good at swapping resistors and capacitors out on the circuit of the tach itself. Yes you do have to take it apart. You have to un solder and re solder the circuit up to read the correct hits per rev. On a gasser it runs of the ignition system. Since there isn't any electrical things making the diesel fire and the alternator doesn't spin the exact revolutions as the crank you have to mod the tach. The crank pulley is different sized then the alternator. There is also a method that you can use a sensor that is run off a pulley.
http://www.4crawler.com/Diesel/CheapTricks/Tachometer/index.shtml
The tachs I have in aren't the most accurate but they work. The car goes down in rpm as the car warms up and the truck is different with and without the lights on. I played with it a lot and basically what my electrical engineering teacher had told me is that if the solder isn't perfect then that can change in resistance with the different temps. Hope that helps you. Let me know if I can answer any other questions on that. Finding an alternator can be a challenge with the W terminal. Also you can move the gauges to work with the original circuit. You do have to cut on piece off from the clock but the fuel and temp gauges still work in the different positions.

Click to expand...

hey dooboongle,
are you going to let us know about


'temp gauge vs. radiator fan'? and how that worked out?

Oops!!!

Sorry about that. Yes, meant to, but have been involved in slowly ... due to fused spine ... clearing off snow and ice for where to put the pickup temporarily. Temperature here has dropped to below zero in the last week. Today is better, and hopefully tomorrow will be also.

Regarding the gauge, rad. fan, etc. ,,, according to the 'expert', it was a defective relay. He claimed that while he was 'jiggling' around with the wiring, etc., suddenly the fans came on A-OK. At the moment, in my short driving of it home, the temp. gauge did register; but with the cold temperature outside, did not hear the rad. fan come on. That's on my list of things to do once I get it where I can begin ... hopefully in the garage once boxes, etc. are put back on shelves.
Chuck

valvecrusher said:

hey dooboongle,
are you going to let us know about


'temp gauge vs. radiator fan'? and how that worked out?

Click to expand...

Take a picture of under the hood and post it here, please.

I'd like to see this project, if you don't mind.




Jiggling wires never fixed a 'bad' relay.

Relays go bad, they don't intermittently go bad in 'spells.'



And the fans + temp gauge both on the same relay? Whatever happened to the 'sensor' issue?

The white, blue and red wires are for the gas check ups that after a certain set of mile there is a gear that sets those wires off to lights I think. I messed with it for a bit but didn't worry about it. I was more trying to find a speedo with a good gear in it as the plastic gear breaks a lot.

http://www.vwdiesel.net/forum/index.php?topic=3741.0

This is what I used and I even posted my results on this. If you go to about mid page on the first website I gave you it states how to connect the "W" terminal to the tach. You do have to cut a little bit of the circuit out. The screw that aren't connected to anything hold the tach together. You need to take those out to get to the insides to make the tach into a diesel tach.

Question for any 1982 plus rabbit diesel tachometer

As disclosed by this thread, I am involved in trying to get a gasser 1982 tachometer to work in my diesel 1981 pickup. In studying 4crawlers website, have come to the conclusion that in order to do so, need to install my 'W' alternator and a Dakota DSL-1 tachometer interface.

Once installed will then connect the 'W' terminal to the DSL-1 input terminal. It, DSL-1, will then convert the incoming signal to a usable output for a 4-cylinder signal to go to the tachometer.

In discussing the 4crawler article with the writer, he advised he put the article together using a rabbit that had the upshift. My pickup does not have that option. Thus much of his details are not completely in compliance with my truck.

So what I need from a diesel tachometer rabbit-Golf-Cabriolet-etc. vehicle, of 81-84 vintage, is to try and determine which tachometer post terminal is used to accept the signal that feeds the tach. There are 3 posts, and 4crawler did not know which one to suggest ... and no longer has his vehicle to look at.

Below is a picture of the tachometer in my modified cluster, with the original diesel mylar circuit board, and shows up at the top the 3 threaded posts (with nuts) that come from the tach.