Battery charge light stays on '85 Golf. Help.

Hi, The battery charge light on our '85 Golf (1.8 L gas engine) came on this afternoon and stayed on.

Tonight I did some checking. The battery was low on liquid and topping up the 6 cells took a total of about 250 ml of water (about a cup).

I started the engine and the light stayed on. Revving the engine usually kills the light but not this time. Light stayed on

Next I checked the alternator output and there is 14.3 V across the battery terminals. Bently suggests between 13.5 and 14.5 V is normal so at 14.3 V the voltage regulator seems to be okay.

Posts in the archives of rec.autos.makers.vw.watercoold suggested checking voltage along the circuit starting at the D+ terminal on the alternator to the charge indicator light and back to the POS battery terminal. Results using a digital multimeter:

Voltage from D+ terminal to ground = 11.68 V Voltage from battery + terminal to ground = 14.43 V

Is it normal for the D+ terminal to be putting out such a low voltage relative to the charging current?

Any suggestons on what to check next? The alternator, an after-market one from Canadian Tire (auto parts store), is about 8-1/2 years old with 80,000 km on it (50,000 miles).

Is it okay to run the car until I figure out what the problem is--any damage I might do?

thanks very much,

-Tony

-------------------- twong(at)vcn.bc.ca Vancouver, BC Canada

Reply to
Tony
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In my experience, the voltage regulators are much more accurate than the

+/- 0.5V limit specified (mine have been within +/- 0.05V, sample size 3). The fact that your battery is loosing liquid and that you are reading 14.3V could mean that you actually do have a voltage regulator problem. Try measuring the voltage again, but this time gradually increase the engine speed from idle to, say, 3000 RPM. See if the voltage increases with RPM. My hunch is that it will increase. If it gets up above 15 volts (number pulled out of my behind, always cite your sources), abort the experiment. Overvoltage can cause all sorts of damage, including ruining the battery. If the voltage stays within the 14 +/- 0.5V spec regardless of RPM, the voltage regulator is fine, otherwise it is probably busted. The most common fault for voltage regulators is to full-field the alternator. At idle the alternator can not deliver a lot of power, so the voltage may still be OK. As you increase the speed, the alternator can put out more power, and if full-fielded will increase the voltage.

If the regulator is indeed broken, I would not drive the car until it is fixed. For that generation VW it is possible to replace the voltage regulator only. 50 k miles is not that much, so I would probably try replacing the regulator only, rather than the whole alternator, should it turn out to be a voltage regulator problem.

T>

Reply to
Randolph

Hi Randolph, Thanks for the quick response. Just went out to run the tests. This time the voltage across the battery terminals was 14.68 V at idle and went up to 14.70 then settled back to 14.68 as I increased the engine RPM.

I observed the brightness of the charge indicator light more closely this time. On starting the car, the charge indicator light was it's normal brightness, on revving the engine, I could tell when the alternator kicked in as the brightness of the dome light increased slightly (normally happens) and the charge indicator light dimmed a bit.

What do you think? Faulty regulator? Unfortunately, it isn't obvious if I can replace the voltage regulator on this after-market alternator. There isn't the brush/regulator setup that I rember being on the original alternator (on the side opposite the pully). But I'll check with the parts store, the regulator inside the current alternator may still be replacable with some disassembly. I bought this one because I needed it on a Sunday in 1996 and Canadian Tire was the only place open with one in stock. My preference is stock VW parts for key components.

I'll park the car until it's fixed. You're right, normally I don't lose that much water from the battery and usually it's only from one or two cells. This time, all 6 were down and down a considerable amount, about 40 ml each. So something is amiss.

Any other thoughts? Thanks again,

-Tony

-------------------- twong(at)vcn.bc.ca Vancouver, BC Canada

Reply to
Tony

t4he wiring between your battery and alternator and starter may have turned to green dust!

this happened ot me.. hard to blieve but yes teh wire just corroded away/disappeared/returned to dust.. apparently vw has been using strange copper in its wiring ..

so check it out.. maybe you can check the continuity of the wire using an ohm meter.. it has been a long time since i repaired my wiring by building a whole new harness using quality copper wire i bought at a hardware store..

good luck

T> Hi,

Reply to
hyubso

Per your original symptom, did the alternator light stay on ALL the time (i.e. even when the engine was turned off?) or just didn't extinguish when the engine was running (i.e. turned on with the key as normal, but didn't go off when the engine started)?

I've had both symptoms occur on different (VW) cars...the former ended up being problem with short in diodes in the alternator, the latter was due to problem with the voltage regulator/brushes (on my A2 Golf GTI).

Not sure about after market alternator...on my '86 GTI, the regulator/brush assembly was very easy to change (after disconnecting the battery cables)....as I recall, disconnect the wiring connection, and remove 2 screws, the whole assembly came off the back of the alternator, no need to even remove the alternator from the car. The brush/regulator assembly was about $25-$30 US. I also noticed a "pulsing" symptom in the headlights and dash lights when the car was running when I had the bad regulator that went away with the new brush assembly (actually, I got a bad one, and had to replace that assembly again due to the bad part).

Reply to
Tom Flynn

Hi Randolph, I checked with Canadian Tire and on that model of Brand X alternator, the voltage regulator isn't replaceable. So I bought a rebuilt Bosch from a VW parts store and am happy to report that solved the problem. Popped in the new alternator, started up the car, the red light stayed on as usual until I rev'd the engine a bit and when the alternator kicked in, the red light went out. Beautiful. Voltage across the battery terminals is 13.95 V, within the range you observed (does that make your N=4 now?).

Original Bosch lasted 150,000 km Brand X lasted 50,000 km

Thanks!

-Tony

-------------------- twong(at)vcn.bc.ca Vancouver, BC Canada

Reply to
Tony

The light went out when the ignition was turned off. So consistent with your #2 scenario of the faulty voltage regulator.

I recall the V regulator being on the outside on the original Bosch alternator as I checked the brushes periodically. On this after market one, everything was inside the case. Today I went with a rebuilt Bosch at a $50Cdn premium over the brand X one. This Bosch has the familiar V regulator and brush assemby accessible from the outside.

Regards,

-Tony

-------------------- twong(at)vcn.bc.ca Vancouver, BC Canada

Reply to
Tony

Thanks. The wiring isn't in great shape being 19 years old, but it looks serviceable. Other than around the battery connections, no sign of corrosion or copper salts.

-T>t4he wiring between your battery and alternator and starter may have

-------------------- twong(at)vcn.bc.ca Vancouver, BC Canada

Reply to
Tony

Yep, probably bad regulator.

Yep, I ran into this on my Mother's car (an old '88 Ford Tempo)...the darned Alternator needed to go to the shop to have the internal regulator replaced, I could find no way of opening it to get at the regulator.

Yes, the Bosch alternator on the '86 was very easy to service...mine still had original when I sold it in 2000. I haven't looked at the alternator on my 2000 Golf, but I hope it is as easy to service as the one on the '86 was.

Good luck with your new alternator (and congratulations on fixing your symptoms). Top off your battery with water, and you should be all set > Regards,

Reply to
Tom Flynn

Reply to
Randolph

hi Randolph. How do I get the battery tested? Probably not something I can do at home. I saw batteries on a test bench at the Canadian Tire store. I think they were doing a load test. Is that what I need?

thanks,

-T>Glad you got it fixed. Now you can only hope that the battery didn't

-------------------- twong@SPAm_ME_NOTvcn.bc.ca (Remove SPAM_ME_NOT from email address) Vancouver, BC Canada

Reply to
Tony

Depends how deep into this you want to dig. Apparently many auto parts stores, like Kragen/Checkers/Chuck, Pep boys, AutoZone etc. will test your battery for free. I have never had them do this, but would assume the go through a set of measurements under a set of loads.

What I do is I just measure the battery voltage before starting the car after it has been sitting over night. If I see 12.6V or above, I am real happy.

Some people suggest turning on the headlights for several minutes, then turn them off and wait several minutes before making the measurement. This will remove any surface charge in the battery. From what I understand, this is not required if the battery has been at rest (no charging or discharging) for 6 - 12 hours.

Reply to
Randolph

Thanks, I'll go test the voltage in the morning. I presume a damaged battery will show less than 12.6 v then. I'm still impressed how the charge indicator light works, being connected to the positive from both the battery and the alternator. If both voltages are equal, there is no difference in potential and therefore no current. If there is a diffrence, then there is current and the light illuminates. Elegance in simplicity.

Thanks again for all your help

-Tony

-------------------- twong@SPAm_ME_NOTvcn.bc.ca (Remove SPAM_ME_NOT from email address) Vancouver, BC Canada

Reply to
Tony

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