# Tachometer and Electric



## DAVEG (Aug 14, 2001)

I have been having tachometer problems...runs then stops. The unit seems fine for several weeks and then it stops...when it stops it doesn't work again until the car has been sitting for several days. There is also problem with the backup lights staying on and then going out and then on again whe the car is not in reverse. The door buzzer seems to work some times and thne not. The battery discharges if the car is left even though the battery is disconnected. 
I removed the gages and looked at the circuit panel but I really don't know what to look for. IS the Tach problem part of an electrical problem or a faulty conection? What should I look for as far as the ground? The rest of the signals and lights work fine.


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## where_2 (Jul 21, 2003)

*Re: Tachometer and Electric (DAVEG)*

search the Mk1 forums for "fuse OR relay AND panel". I've heard some amazing stories about what a flaky fuse/relay panel will do. 
Door buzzer is a corroded switch. remove the phillips screw from the switch in the door pillar. There will be two wires attached, one brown, one likely brown/red. Clean the switch contacts with fine (600) sand paper. reinstall. 
Backup lights are the backup light switch on the transmission, unless it's an automatic. If it's an automatic, I think the switch is under the shifter surround. 
Battery dies even when disconnected. That's called a "bad cell" when the battery self-discharges to less than 12v in practically no time. Replace the battery.


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## DAVEG (Aug 14, 2001)

*Re: Tachometer and Electric (where_2)*

Thanks...I will check. ELectrical problems are always a problem.


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## DAVEG (Aug 14, 2001)

*Re: Tachometer and Electric (where_2)*

My recent problem is with my tachometer. Does VW use a alternator diode to run the tachometer?


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## DropTop81 (Apr 25, 2009)

*Re: Tachometer and Electric (DAVEG)*

I have an 81' Rabbit Convertible. I too had many of these issues my self. I finally ended up pulling the fuse relay panel out. The connectors on the back get wet because there is an inherent leak from the bottom of the windshield lower left corner, or that general area in the rain tray on most MK1's. That leak needs to be fixed to stop the problems permanently, however to get things working again you will need to pull the panel, and then clean every connection you can get to. I had to replace several relays as they had become rusted up inside from moisture and several push on female spade wire connectors as they were corroded to badly to clean. I also found that many of the pins in the main wiring harnesses were simply rusted into or just rusted away, and had to run new wires with external in line fuses.
You can get a new front and rear harness, and a newer style panel that uses the flat push in fuses, but it is a real beast to pull the old harnesses out and then the replacements back in. If you do go that way, I would get an aftermarket harness, as the German harnesses use an inferior grade of connector that is not coated with Zink to reduce rust and corrosion, and the wire is of minimum size and quality to make each circuit work.
I also had to use my dremel tool to wire brush each fuse contact and every pin connection on all of the plugs on the main harnesses, and every male spade connector on the back and top of the fuse and relay panel. After that and replacing the connections that were just un-repairable and installing in line external fuses everything works now.
The windshield is cracked thanks to a tractor trailer rig tossing large rock at me, so when I pull the windshield to replace it, I'll seal the hole with JB Weld, and bondo.
And yes someday, I will get the nerve up to replace the panel and harnesses with the new and improved units.
Good luck!!


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## DAVEG (Aug 14, 2001)

*Re: Tachometer and Electric (DropTop81)*

Drop that is exactly my problem a leaky front panel...I had the rockers replaced and the body shop removed some dirt for the front drainage areas. I will have to make this a priority. 
Who sells an aftermarket harness? I have the interior out and am replacing the carpet so I might as well do this too. I feel like I am rebuilding the entire car.


_Modified by DAVEG at 1:26 AM 8-21-2009_


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## where_2 (Jul 21, 2003)

*Re: Tachometer and Electric (DAVEG)*

Regarding the tach signal: VW usually only uses the alternator method if it's a diesel. Usually they use a red/black wire that comes off the ignition coil under the hood to feed the tach, but it goes through the infamous fuse/relay panel on its way to the instrument cluster...


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## somolovitch3 (Nov 3, 2006)

*Re: Tachometer and Electric (DAVEG)*

Backup lite problems caused by fried backup lite switch on trany.
Its held on by two 9mm headed bolts. Be prepared to spend long time with open end wrench removing and reinstalling said bolts.
I have a relay set up to handle the current using the existing wire to run the relay and new 14 ga wire back to the bulbs.
Enjoy!


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## DAVEG (Aug 14, 2001)

*Re: Tachometer and Electric (somolovitch3)*

I know I replaced this Backup switch once before and it was a large diameter hexhead threaded switch. I have been trying to find it on the transmission with no luck...it is under the air box.


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## where_2 (Jul 21, 2003)

*Re: Tachometer and Electric (DAVEG)*

But to remove the airbox, you unlatch the latches, and gently lift it over and out of the way. Then you remove the bottom portion so it is completely out of your way. I know it doesn't have much slack in the fuel pump and fuel return lines... It's not like you're going to be ale to toss it over the fender... 
Of course, I got my practice doing this on an '80 Scirocco_S into which I installed KE_Jetronic FI. So, I had every hose you have, and 2 more... Take off the hose between the elbow over the air flow meter, and the throttle body...


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## DropTop81 (Apr 25, 2009)

*Re: Tachometer and Electric (DAVEG)*

A couple of things Dave...
Before you tear your fuel distributer apart.... Have you tried using a simple single pole switch to test the backup light circuit?
The backup lights or reverse switch is a hex screw in switch, on the 5 speed Tranny (not held in with 9mmm screws, and easy to swap out)right on top of the tranny just about in front of the master cylinder. It has a plug with two female spade connectors. You should be able to reach it without tearing half the fuel distribution and air filtration system off the car.
Try just connecting a plain switch with two male spade connectors connected too a couple of wires about three feet long. With the E-Brake set, turn on the ignition switch (don't start the car) and then flip the switch.
Check to see if your back up lights are on. If so, wiggle the connector around hard, check the lights again. If they go out, you need to replace the connectors. or there may be a break in one or both wires. Inspect and replace as needed.
If this all yields no joy, the you can also check the operation of the switch with out removing it as well. You can use a ohm meter or continuity tester, most DVM's have a built in continuity tester with audible alarm. Just connect one lead to one spade on the switch, and the other to the remaining spade connector on the switch. Do the same test. Turn on the ignition, put the Tranny in reverse, if you get continuity successfully several times, your switch is probably working fine, and the issue lyes in the wiring or fuse panel connectors.


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## DropTop81 (Apr 25, 2009)

*Re: Tachometer and Electric (DropTop81)*

Also Dave, if you haven't bought a Bentley manual yet, you need to. it is a life saver in time and info.
Here is just one link to a fair price: http://www.partsgeek.com/catal....html
Be careful buying one off of eBay, I have three, and the one I got off of eBay was listed as very good condition, the pages are falling out, and I have only had it a couple years. I'd try Powel' Technical Book store as well. Or hey try here: http://michaelbentley.com/isbn....html


_Modified by DropTop81 at 12:04 AM 8-25-2009_


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## DropTop81 (Apr 25, 2009)

*Re: Tachometer and Electric (DAVEG)*

Believe it or not CarQuest can usually get almost anything VW. They have a Euro Parts partner. I have been able to order at a reasonable cost just about any part I have needed and get it in a matter of a day or two.


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## DAVEG (Aug 14, 2001)

*Re: Tachometer and Electric (DropTop81)*

I took the car to a mechanic and he inspected the Backup Switch and Said it needed to be repplaced but when I got it form Rabitt Parts it was the wrong part #. 171919823A instead of 171919823. The right # on the order form but not on the part.
The quest continues.


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## doonboggle (Jul 27, 2007)

*Re: Tachometer and Electric (DAVEG)*

Good luck on the backup switch. I just went thru this same thing ... from Kragen parts. It was not their fault, but the chinese manufactor who makes them these days. The legs of the original switch ... screw in type with two legs ... are long enough to fit into a depressed plug on the factory wiring harness. But the legs on the 'todays' version, are much shorter ... thus making one have to extend the harness with a jury rigged extended 2 wires. I looked and looked and looked on the web, and every source showed the same type.
Finally I came across a source that had posted an image, that was of the correct leg length, and in contacting him, he was kind enough to order on thru his supplier (did not have one in stock) with no charge to me ... to make sure of the length. Came back as OK, and I immediately ordered 2 from him ... one for now, and one for prosperity.
Did you ever get the tach working .... and is the alternator one of the 'W' types that it ... tach ... is wired into? 
I've found a tach but have read that the alternator must have a connection, labeled 'W'. Otherwise I'm looking at a jury rig that 4Crawler has posted on his site.


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## doonboggle (Jul 27, 2007)

*Re: Tachometer and Electric (doonboggle)*

^


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## DAVEG (Aug 14, 2001)

*Re: Tachometer and Electric (doonboggle)*

I fixed the backup light with a new switch from a local autoparts store. The tach is still cutting out intermitently. I think there is a loose connection. #171919823A backup light switch part works after all.


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