upstate bob

as another 79 owner I have little trust in the panel volt gauge. Next summer I will take readings with an accurate one. I notice an extra wire coming off the hot post on the battery. Is that original like VWs have or did someone tap in for radio or speakers?

Mrmerlin

if anyone is tackling the odometer repair now is also a good time to adjust the volt meter so it reads what is actually coming out of the alternator.

To do this remove the pod gauge pack , then the rear housing.
This will expose the alternator gauge,
find the rheostat,

place a towel onto the steering column,
plug the gauge pack into the connectors ,
rest the gauges on the towel,
start the engine ,
then take a reading at the hot post ,
then adjust your alternator so it reads the same as your reading,

put the pod gauges back together

Randy V

It looks like the interior lights stayed on after closing the rear hatch, draining the battery.

My rear hatch lock switch just barely actuates when the hatch is closed. Is there any way to 'raise' the switch so it activates at a higher position?

87landshark

I had my 87 5-speed out last weekend for what was probably the end of the good weather here on long island. After making several stops, upon restarting the car, the dash lit up like a Christmas tree. Every possible warning light was lit, including the low oil pressure and the highe coolant temp lamps, belt tensioner, brake fluid, brake pad-you get the idea. The voltmeter gauge, which has always wagged like a dogs tail for YEARS was pegged at ten volts ( I have never seen it so low) I used to get 13.25-13.75 back at the battery post, now it's low 12's. The battery is about a year old and is kept on a Schumacher trickle charger all the time. Would a failing alternator-voltage regulator cause the dash to light up the way it did? Eventually it cleared up during driving and I got the car home, but it did reoccur again once upon pulling onto my town. What does the shark tank recommend? Grounds to chassis were done (cleaned) not too long ago

Alan

It is the alternator regulator for sure - that is the only thing that causes these symptoms.

The low voltage is because the alternator isn't generating, but the lights all come on due to the exciter line being driven low. Unless there is a short to ground on the exciter line - the only thing that can make it go to low voltage is the alternator regulator. An open circuit won't do it.

Now you have seen this - do the dash lights ever go out after starting?

Take the alternator in for testing - while the regulator isn't working - other faults in the alternator could be the cause of that so a full check over is in order. Remove the electrical connections first - don't dangle the alternator from the wires. Find a good local alternator/starter specialist shop if you can.

Alan.

Randy V

I'm not feelin' the love.

Alan

OK - so I haven't done this - but I think you can change it. The switch is very open air and visible - but you have to remove the hatch receiver first to see it, it is an integrated part of that.

Make sure you have a good location defined for the reinstall of the receiver (masking tape frame around it maybe?).

You also need to pop the arm/cup off the hatch release motor cam, and disconnect the pin switch wire. Will need to remove the protection plate to be able to do this.

With the receiver out you can see how the pin switch works - terminal in the bottom connects via the white plunger pushing down against the spring - case is grounded

You need to screw/shim the bottom contact up or bend the contact up just a little for earlier contact. You may need to do some disassembly and fight with the spring a bit - but should be doable - biggest risk I see is the realignment of the hatch receiver on reinstall. You could see if there is any adjustment you can do with it in place - but this will be challenged for visual & manual access.

Found this pic that may help visualize.



Alan

Randy V

I'll give it a shot. Thanks, Alan.

87landshark

Yes, thank you Allen. It is as I suspected, but I always ask the shark tank for confirmation. I will certainly be replacing the alternator with a quality rebuilt one, instead of just plugging in a new voltage regulator. Thanks again for your verification.

SecaBlue

I wanted to revive this thread with some findings from my '93 GTS done 134,000km. (German car).
According to what I read above, I think that my alternator is working fine, and I have good voltage at the jump post. My battery is new from the beginning of the year, and I keep it on a 10A trickle maintenance charge when I am not driving it for long periods. My findings are as follows:

Car unlocked but ignition not on: 13.2
Car with ignition in 'on' position but not started: 12.9
Car started at idle with no lights or A/C: 14.3
Cold idle with headlights only: 14.2
Cold idle with headlights, fogs, high beams: 14.1
Cold idle with as above plus A/C: 14
Warm idle with all lights and A/C: 13.3 to 14.1

Gauge reads a fairly consistent 1v less before start, and approx 0.5v less after start.

What I find a little unusual though is the engine behaviour at warm idle behaviour - When I have the alternator under load with all lights and A/C, the idle fluctuates from just under 800 (indicated) to just over 600. This causes the warm idle volt readings at the jump post for the last line above. The idle oscillates up and down every 15 seconds or so between those rpm, and the gauge shows this rise and fall of the volts too with this engine speed. Any ideas what can be causing this? Turning off the A/C stops it immediately even with all the lights on. so that is a clue. A/C works perfectly btw.

And, no. I have not cleaned any ground points at this stage.

FredR

Sounds as though you likely have a problem with the idle control valve that may be sticking some- that or needs replacement as they do from time to time and as may well now be the case with 134k km on the odometer.

A fully charged battery should show about 12.8 volts with no load. Maybe the battery tender is keeping such a bit higher than normal.

SecaBlue

OK, I'll check on the ICV 👍

regarding fully charged battery.. I have a similar spec marine battery on my boat, which is trickle charged by a 2.4A solar panel. The regulator always shows the battety at 13.1v no load, no sun.

GregBBRD

I'm not sure you could have a more perfect battery/charging report better than you have.
Surging at idle, on an S4, is almost always an overly rich condition.
Start by pulling the vacuum hoses off of the fuel pressure regulator and the dampers and see if there is fuel pouring out/inside.
(Extremely common at the age of these pieces.)

SecaBlue

OK and if it is, what do I do next? :P

FredR

Make sure your wallet is well packed!

Unfortunately if one of the three control devices in the fuel delivery system goes it is probable that the other two are not far behind. The stock items are outrageously expensive at around US$600 per item these days. GB does an alternative setup but as I recall he has temporarily pulled them due to some quality control concerns he has. Roger [928srus.com] also has some after market options as I recall.