A1 Electrical - Reverse kills inst. panel lights & drains battery

Hi everyone,

I guess this forum is full of unanswered questions but I'll toss this one out just in case. If the long time VW owner/mechanics of this forum can't answer this, noone can!

Just bought a nice 1984 Rabbit GTI, all is well except for the electrics. Last guy to own it tried to fix stuff by twisting wires together & duct taping. A VW garage has said that the alternator is new, but there is something that is stopping the battery from charging.

I suspect something in the shifter is causing some of the problems. To start with, the reverse lights won't come on when the car is put in R. Secondly, whenever I put it in any gear the lower instrument panel lighting (battery volts, clock, engine temp) goes dead and won't illuminate until I put it in neutral and wiggle the shifter. Strangely, the main instrument lighting (which is on the same fuse as the lower panel's) stays on.

Has anyone had any experience with a problem like this? I don't want to start tearing the shifter apart until I know what I'm doing! Will be buying the Bentley manual tomorrow.

Many thanks,

-Antony

Victoria, BC, Canada

Reply to
Shaw News
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Check and clean the ground cable from the battery to the body and the engine/trans. Make sure that it is very clean and tight and in good condition. Your alternator might require a separate ground wire/cable to the engine. I would start there first.

later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

Reply to
dave

Antony,

The problems that you describe could be caused by many things and are almost impossible to troubleshoot over the internet. When I bought my 81 rabbit convertible it came with three manual switches (two of which were hidden inside of the dash) and the owner had no clue what they were for. Also I found that the alternator wiring had been burned through. So I feel your pain, but luckily I do electronics for a living so I was able to figure it all out. For your problems I'll give you a few of things that I learned while I was troubleshooting mine.

First of all for the battery/alternator problem. There should be three wires coming from the alternator. The two big wires (Probably Red) that go to the battery to charge it and then a small wire (mine was blue). The blue wire eventually goes to your instrument cluster where it basically checks the 12 V signal there to tell the voltage regulator in your alternator to raise or lower it's output voltage to the battery (simplified explanation). If this wire is broken or disconnected (or not seeing 12V at the instrument cluster) your battery will not be charged by the alternator. So assuming that you have had both the battery and alternator/regulator checked (if not get it done many parts stores do it for free) then this wire is a good place to start.

For the reverse light problem. On top to the transaxle in front of the speedo cable is you backup light switch. Depending on your model of car it is either a round two wire switch that just screws in or it is a multi-wire (4,5,or 6 wire) square switch that is L shaped and is held in place with two bolts. Both switches only use two wires for the backup lights. When you shift into reverse the transmission selector (inside of the tranny) presses up against the switch and connects two wires to provide a path for 12 V to your backup lights. The tail light assemble applies ground permanently to the other side of the bulbs so that current can flow through the bulbs and the lights turn on. If you have the two wire switch this should be easy to trouble shoot but from you explanation I would assume that you have the multi-wire switch. I've never worked on a car with the multi-wire switch but as I understand it the other wires in the switch are used to tell the car what gear you are in. and different wires are connected for different gears and again this all goes back to the instrument cluster eventually (common component to both of your faults?).

To figure out what is all going on you are going to have to get some wiring diagrams. I strongly advise you to shell out the bucks ( or in your case loonies) and buy the Bentley manual for your car. With the problems you have, it will pay for itself in no time. Auto shops suck at troubleshooting electrical faults and charge by the hour so there inexperience ends up costing you a fortune.

I hope this helps somewhat. Post what you find and the group should be able to help you through this.

Steve

Off topic I live down in Bremerton Wa, and have been to Victoria many times. Awesome City with great people can't wait to get back again.

Reply to
sehaare

You didn't mention if the car was manual or automatic (don't know if the '84 GTi was available in auto). My experience is with the A2, and may or may not apply to your car. When I first got my car (used) the backup lights did not work. I found out it was the switch, but had a hard time finding a replacement that would fit. The car has an upshift indicator and needs the big expensive combo switch that also tells the upshift indicator circuit that the transmission is in 5th (no point in turning on the upshift indicator when there is no higher gear to shift to). Turns out the previous owner had replaced the tranny with one that did not accept the big combo switch. The wires from the two-wire switch I needed was spliced into the 5 wire harness in the car. If your car has duct tape type wiring repairs, it may be worth checking the wiring to the backup switch.

If the car has automatic transmission, the switch for the backup lights is typically located at the shift lever and not on the tranny.

Another thought is that if a previous owner had a remote start system installed he could have rigged up some sort of circuit to indicate that the tranny is in neutral. One might speculate that not too much care would be exercised used when removing a remote start system...

Sehaare also had some very good suggesti>

Reply to
Randolph

So the blue wire is for the field winding! I learned something new today. I always thought it was feedback for the voltage regulator and the schematics were never specific enough to show other wise.

Steve

Reply to
sehaare

In the good old days it did provide current to the field winding through the voltage regulator. After the alternator started delivering power, the field winding current was supplied from the alternator itself. In new designs it is really only an ignition sense but it is still required to turn on the field winding current. Look at

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foran example of an integrated automotive voltage regulator.

Reply to
Randolph

Thank you Dave, Steve, and Randy! Wow, three responses within two hours. Can't beat that.

Just got back from two hours of drooling on my car... because I had to hold the flashlight in my mouth while fighting with the battery ground wires!

Found three wires that went off the battery. Large copper braided one went to a lug on the transmission, had a second extra grounding lug on it midway along that wasn't used. Couldnt' find any lug on the frame to attach it to. Small insulated one went (as far as I could see) to the engine mount arm. Large insulated one dissapeared from sight under the air filter. Cleaned all the contacts I could reach and snugged the battery back in. Sound ok, dave?

I think the alternator field winding wire is connected okay. Here is a more detailed diagnostic.

Battery gauge in the cockpit works, verified with a multimeter. When the car is just started the battery gauge reads a happy 12 V until I rev it past

3000 at which point the battery light on the dash clicks off and the meter goes up to 14V, staying there as I go back to idle. Sounds good so far.

Shifting the (manual) transmission into any gear with the lights still off only makes the battery gauge jiggle, down maybe 1/4V at most.

If I pull out the lights knob half way (running lights only, no headlights), the main instrument panel and the auxiliary gauges light up OK and the voltmeter continues to read 14V. If I then shift into reverse, all the auxiliary gauges' lights die, the voltmeter drops to rock bottom, but the main instrument panel is unaffected. Taking it back to neutral brings the auxiliary gauge lights back on and the voltage back up to 14. Couldn't verify the reading on the battery leads as I didn't have a friend around to keep the clutch in with the tranny in gear while I ran around under the hood.

Randolph, there wasn't a remote start system ever installed that I know about, however there was a car alarm installed at one point, the brain and horn are still present though all the (visible) wires have been cut. Doubt it would want to know about the car being in gear, however they might have hooked it up to the ignition? Doesn't seem too suspect.

Steve, I dug around under the car as best I could but I wasn't sure where to look for "On top to the transaxle in front of the speedo cable" for my

6-position shift sensor switch. I'll get to know the navigational names once I have a manual. There is a little light on the floor of the instrument cluster dead center that might be the upshift light Randolph mentioned. I will try and investigate the 6-position shifter switch further, that sounds like the likely culprit.

It sure is hard to think without a wiring diagram in front of me. Would the six position shifter indicating switch be shorting to ground? Why only affecting the three auxiliary gauges and not the main instrument panel? And not blowing any fuses that I can see?

What a joy, eh? Thanks again for the help, let me know if any more ideas come to mind!

Cheers,

-Antony

Reply to
Antony Hilliard

The second connection of the large ground wire was supposed to connect to the frame. If they were two different sizes the large cable to the engine and the smaller for the body.

Your alternator works typically for one that has a bad exciter wire. That blue wire everyone was talking about is supposed to get the alternator charging at 800 rpm without having to rev up the engine. An alternator will usualy start to charge if spun fast enough. In days of old alternators sometimes had a resistor pack (like the one used on a Chevy to drop the coil voltage down to 9 volts) instead of the alternator light wire

Many make an auxillary ground wire from the alternator housing to the engine because the factory ground strap goes bad.

I would unplug the backup lights wir>

Jim B.

Reply to
jimbehning

Check the ground for the lower gauges. If you pull the shifter boot, the ground is attached to one of the screws that holds the console to the floor. In my case, the lower gauges worked when the headlight switch was off, but turning the lights on killed them.

Robert

Reply to
Robert Kidd

Bingo - the ground screw was all rusty and tarnished, I filed it up, scotch-brited the rest, covered in dielectric grease and tightened it down. Seems to have fixed the instrument lighting problem. Thanks!

Got the battery grounded with an auxiliary strap to the car body too, that couldn't hurt.

Still haven't gotten to the bottom of the back-up light problem, I am looking at the transmission and can't see where the back up light switch attaches... maybe it has just been removed on this car? There are a few cables that are just floating loose in the engine compartment.

Will investigate more when it's not so wet out. Thanks again for the help.

Cheers,

-Antony

Reply to
Antony Hilliard

Hi Steve, all,

Well, I guess it was a predictable ending, I finally (with Bentley's help) found where on the tranny the 5-position switch was, jumpered the appropriate pins on the plug to simulate a closed transmission reverse switch and bingo, both back-up lights came on.

Tried (in the cold and rain again, damn west coast weather) to test continuity on the transmission switch when the tranny was in reverse, and came up empty. I couldn't be sure, but I swear I hit those pins a few times with the multimeter but there was no signal. So either the transmission parts that are supposed to hit the switch are worn down or the switch is toast.

Judging from the feedback I've read on the 'net, it's probably the switch. It's not easily accessible without pulling some stuff off the engine so I guess I'll just live with the lack of revere lights for now.

Thank you again for your help!

Cheers,

-Antony

troubleshooting

Reply to
Antony Hilliard

For a quick temporary fix (I've done this in a couple of cars now) Run your jumper wire to a manual switch in the car. For about $10 in parts (wire, switch, crimp connectors, tape) you'll be able to turn on your back up light when you need them until you get this fixed permanently.

HTH Steve

Reply to
sehaare

Jim B.

Reply to
jimbehning

I missed the orginal post but...

I think that you are talking about a late model A1 back light switch, the one with multiple pins... and very very small contacts inside. It is very easy to open that swicth and swap the burned out contacts with the good not used one.

Being at it, add a relay (used to be a $5 Radio-Shack part) between the backup light switch and the back-up light. I do not recall the exact number, but the back-up light draw something like 3 or 5 Amps. Either way this is too much for the very small contact inside the switch.

I did all of the above when I was driving around in a A1... I did more than 400 000km without any additional back-up light problem.

Good luck

Martin Quebec, Canada

Ant>Bingo - the ground screw was all rusty and tarnished, I filed it up,

Reply to
Martin Boulerice

Big thumbs up to everyone who posted advice - Jim, Robert, Martin, Dave, Steve, Randy...

The 84 GTI bunny is now alive and well, I have taken the oxygen sensor temperature sensor and the back-up lights and wired them to manual switches in the cockpit. I can now turn the reverse lights on manually as well as enable/disable the lambda emissions system (where previously the temp switch was just jumpered out).

Fixing the reverse switch properly with a load reduction relay as Martin suggested was too much work for me, I just used some SAE self-stripping tap connectors to run off the shift switch cables to my manual switch.

Anyone have any experience with the corrosion lifetime of those self-stripping tap connectors? They are resting above the transmission, gooped up with di-electric grease.

Got the injector o-rings and seats replaced to fix vacuum leaks, she runs much happier now. Still some more leaks to hunt down, I have a feeling they'll never stop!

Cheers, all,

-Antony H

Victoria, BC

Reply to
Antony Hilliard

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