SilvA4Q

Before anyone says to use the "search" button, I just want to let you know I have read over every thread that comes up for a search of "voltage regulator", "alternator problem", "not charging", etc. I just cant find anything that relates to the problem that Im running into.

Background, its a 1990 C2 Cab. that has had the alternator replaced (Bosch Remanufactured) about 20k ago and has a brand new battery Super Start Premium (700 cca, reserve capacity 110). Pictures of it can be found here, Texas Audi Group Forum.

I fully charged the battery with a trickle charger and it brought the voltage up to about 13.3 prior to installing it in the car. Everything started right up, took it for a long drive and after getting back, there wasnt enough juice to start the car again. Trickle charged it again and hooked up the multimeter, when starting the voltage dropped to just above 10v but jumped back to about 12.8 and started declining. This when the car is running, and even increasing revs doesnt bring the voltage across the battery up. I disconnected the negative terminal to check if the car would turn off (tip gathered from another thread) to see if the alternator was dead but the car stayed on, running very slightly rougher then when negative terminal was connected to ground but still running fine. I also hooked up the multimeter to check the voltage with the ground disconnected. Oddly enough the battery was charging, the voltage was steadly increasing. As soon as I reconnected the ground, it dropped about .5v and started decreasing again (at this point around 11.91v).

Am I going about this trouble shooting all wrong? Nothing seems to be adding up about the battery being charged from the alternator when the negative is disconnected but it decreasing when the ground is connected. I know very little about how any switching occurs for the alternator so I dont know if there is a faulty signal being sent to it when the negative is connected or if there is an issue with the ground. Any and all information would be greatly appreciated. I am in the processing of ordering a copy of Adrians book right now to help with this and couple other slight issues.

Thanks, Adam.

mojorizing

Sounds like it could be a voltage regulator problem which is located on the forward end of the alternator. The alternator should be putting out 13vdc +/- when charging.

Indycam

Never pull a cable from the battery while the motor is running ,
you can blow a diode doing that .

If you have not already done the clock ,
its time to pull the clock and redo the solder joints .

SilvA4Q

What makes you think its the solder points on the clock? I have never had the air bag or seatbelt lights come on before but I have had the ABS light flash every once in a while. Not sure the cause of that either.....But wouldnt the charging system of the alternator come on after increasing the rpms to 3-4k? All of the threads I read about the solder points was that the alternator would start charging the battery once the revs increased to above 3k. Is that not right?

I'll pull the clock and look at the solder points, is it possible to see bad points visibly or should I take it to a shop to have the points redone?

Indycam

Have it all redone .
Once the clock is out of the dash , solder everything .
It costs next to nothing .

darth

"I also hooked up the multimeter to check the voltage with the ground disconnected. Oddly enough the battery was charging, the voltage was steadly increasing." The ground wire has to be connected in order to complete the electrical circuit, without it connected charging cannot occur. "Oddly enough the battery was charging, the voltage was steadly increasing." Your meter (i.e. likely the more common Averaging variety as opposed to a true RMS meter) was measuring the DC voltage along with the AC component of the the rectified voltage being put out by the alternator which is typical for a meter on the DC setting . " disconnected the negative terminal to check if the car would turn off (tip gathered from another thread) to see if the alternator was dead but the car stayed on, running very slightly rougher then when negative terminal was connected to ground but still running fine. " Without the battery connected to filter the AC component being put out by the alternator the coils were receiving this noisy (i.e. for lack of a better word) voltage, hence the rough idle. It appears the alternator is puting out voltage but maybe some of the diodes are blown not allowing full output. I'd get the battery load tested first as that is the easiest first step and if it checks out look at the alternator. Do all your dash lights illuminate when you turn the key to the "on" position?

SilvA4Q

Indycam - I've pulled the clock and nothing looks out of the ordinary but just to make sure Ill take it to a shop that resolder all of the points and make sure the solders are correct.

Darth - i took the battery to a local auto shop to have it checked out only a couple days ago and since the voltage was so low they had to put it on a machine that charged it and then "tested" it. I am assuming that it was load tested but not positive. Is there a correct way to test the alternator output without having to pull it and bench test it? Do you think it would be better to take it to a local autoparts store to have their multimeter hooked up for the testing of the voltage across the battery? As for the lights illuminating, they have lit up the same since the car was purchased but this issue has been around since the car was bought also so I am not sure if its lighting up correctly. Should I look for anything in particular?

Indycam

Cool , once the clock is back from the shop and reinstalled , lets do a few tests to see whats going on .

darth

"I am assuming that it was load tested but not positive." Assume nothing, you know what they say when you assume! It appears the battery may have been discharged quite low and sometimes they don't recover 100% and if they do appear to have recovered their capacity degrades. Your testing techniques are fine provided you have confidence in your meter, but I'd avoid disconnecting battery cables while the engine is running as well as running the engine with them disconnected. The battery acts like a capacitor in a way filtering out the raw DC from the alternator, which may have a detrimental affect on the more sensitive electronic components.

SilvA4Q

Indycam - something has caught my eye looking at the solder points on the back of the clock. It appears that at one point some of the solder points were redone, the one most apparent is the furthest right (with clock upright) looks to have been redone at one point. I think it would be a good idea to just replace all like you suggested. What shops would be the best to call around asking about soldering? Do mechanics do this kind of work or are there specialists?

Also, I checked today for what lights that come on when starting the car. Other than the cabrio and spoiler lights, the seat belt and airbag light come on but only for a second or two. The seat belt goes off within a second of starting and then very shortly followed by the airbag. The battery light does start to show when running for a little bit and dims when increasing rpms but after letting off the gas it gets brighter then previously. Does this spring any other suggestions?

Indycam

If you want , buy yourself a soldering iron and redo the solder yourself .
Soldering is fundamental , you should have an iron if you are going to work on cars , imho .

http://www.google.com/products/catal...0BEPMCMAg4AA#p

Melt all the old solder and add a little new solder to the old .

If you really want someone else to do it ,
type Houston TX electronics repair into google .
Find a repair tech who solders every day .

The thing to do is get all the solder done on the clock and put it back in the dash
then we can talk about what the lights mean and what the voltage reading mean .
But lets get the clock redo done first .

SilvA4Q

Im not too confident in my soldering capabilities. I think this time around Ill have it done by a professional. That and I dont want to have to wait on an item being shipped, Im missing out on valuable driving time!!! Is there a way to test the solders/circuit with a multimeter when i get it back to make sure that everything is connected properly prior to installing it back in the car? I'll be taking it to the shop during my lunch break today and getting the battery load tested. Hopefully it wont take too long to have the solders redone.

Indycam

I guess you could test for resistance but I would not bother .
The fact that you can crank over the motor tells me that the battery is working .
The fact that the problem was there before and after the new battery tells me that the battery is not at fault .

Please tell the person who is going to do the rework on the clock ,
the board comes off by unsoldering the 3 little pins . Once the three are melted the board pulls off no problem . Pulling off the board lets the person rework the backside of the board .

wellcraft290

anyone have the link to the clock fix? I used to have it but old computer got fried.

Indycam

Take the clock out of the dash ,
remove all the light bulbs ,
remove the board from the clock by removing the 2 screws and heating up the 3 pins ,
resolder every solder joint on the front and back of the board ,
put the board back on the clock with the 2 screws and solder up the three pins ,
put back the light bulbs ,
put clock back in dash .

For extra credit ,
check all the light bulbs to see if any are burnt out .
If any are found to be burnt out ,
move the extra bulbs around to where they are needed .