Pain in the @#%$ Charging Problem

[Ronnie's.930]

1987 930

A few months back, my alternator/voltage regulator was only putting out about 12.3V - I replaced the VR but did not get the alternator checked (yes I know, "dumb ass me"). The VR was a Huco brand that I did not realize I was getting (read many negative things about them) but I used it anyway. It seemed to be ok for a while but now I have 13.4 volts when the engine is cold/warm (good) but only 12.3 when the engine is at operating temp and the lights and a/c are on (bad). Does this sound familiar to anyone. I guess now I need to take the alternator/VR back out and have them tested (like I should have the first time). . .

[Joe Bob]

Not great at 12.3.....have you tried another volt meter? Does the red idjut light come on?

[Ronnie's.930]

JB - I'm using a fairly new Amprobe that I think is good (sure was expensive enough - ha). I dropped and broke a cheap, turd multimeter that I had used for years, so I just have this one currently.

The idiot light comes on and goes out with the key, as it is supposed to, and does not seem to come on even when I get the 12.3 reading . . .

[Joe Bob]

What does the battery read with the engine off after a drive with the AC and lights?

How are you determining the 12.3v reading when driving?

Has the battery gone dead?

Have you load tested the battery?

[T77911S]

this is what i dont get. so many people sweat and waste time and money on the charging system when you can drive the car to one of these parts stores and they will test your battery and your charging system for free. then just draw your on conclusion based on what they have done for you.
shoot, the guy even put the battery in my car for FREEEEE.
i wonder if, since parts stores will do the work for free, if a mechanic shop will give you the parts for free and charge you for the work?

[boyt911sc]

Originally Posted by T77911S

this is what i dont get. so many people sweat and waste time and money on the charging system when you can drive the car to one of these parts stores and they will test your battery and your charging system for free. then just draw your on conclusion based on what they have done for you.
shoot, the guy even put the battery in my car for FREEEEE.
i wonder if, since parts stores will do the work for free, if a mechanic shop will give you the parts for free and charge you for the work?

Whenever I have doubt about the performance of my battery, starter, and alternator, I simply do my initial investigation and drive to my favorite auto supply or local starter/alternator shop that rebuilt my starter ('78 SC) in 1992.

Tony

[vince_aust]

Getting 12.3 under load is actually ok. The problem is you should be getting about 14v if engine above approx 1500rpm with no significant load( i.e. lights, stereo with amp or AC.)
SO.... If you can check voltage when engine at approx 1500 rpm and volts are approx 14 ( no load) and your voltage is 12.3 under full load (headlights and AC) then I don't think anything is actually wrong

Vince

[Joe Bob]

That's why I asked how the running measurement was taken. I agree 12.3v isn't BAD, it's low. My 3.6 runs on the low side as well, always has. I have never seen over 13v at anytime and it has been that way for years.

As to taking it to a auto parts shop, last I checked it's a bench test unless they have other equipment. A mechanic shop will normally charge a diagnostic fee. Unless you have a prior working relationship.

Most of the posters are DIY people. At least that IS the purpose of the board.

YMMV

[Ronnie's.930]

JB and Vince - I will do as you have suggested later today. Those voltage measurements were taken at 1000-1100 RPM (my set idle speed). I do most of the work on the car by myself, but today, will be able to have my brother run the car at higher RPM while I measure voltage. I keep meaning to install a VDO volt meter, but still haven't done it.

[Ronnie's.930]

Originally Posted by T77911S

this is what i dont get. so many people sweat and waste time and money on the charging system when you can drive the car to one of these parts stores and they will test your battery and your charging system for free. then just draw your on conclusion based on what they have done for you.
shoot, the guy even put the battery in my car for FREEEEE.
i wonder if, since parts stores will do the work for free, if a mechanic shop will give you the parts for free and charge you for the work?

Originally Posted by boyt911sc

Whenever I have doubt about the performance of my battery, starter, and alternator, I simply do my initial investigation and drive to my favorite auto supply or local starter/alternator shop that rebuilt my starter ('78 SC) in 1992.

Tony

Pin a rose on you two, but I prefer to do my own work/trouble shooting and enjoy learning while I do so . . .

[Joe Bob]

Most people (me included) use the hole where the clock is. I have a wrist watch and the digital face on my radio has one as well. I don't need one in the dash, that usually doesn't work.....

Westach, an aircraft gauge company made me a VM and head temp combo gauge for a very reasonable price. Two idiot lights for high heat and low voltage were included.

[T77911S]

i use to do electrical work on cars for a living for a short time. we had a test set that tested the battery and the charging system. places like advance or Oreilys will do this for free.
why not take advantage of what they have to offer.

there 2 things to be learned when it comes to the charging system

1 take the car and have the entire system checked. battery, alt
2 take the alt off the car, have it tested and/or rebuilt

its fine to put a meter on the battery to see what is going on adn to understand what you see. but once you suspect a problem, do 1 or 2. and it sounds like you have a problem.

you already replaced the VR and you are still in the same boat. the problem is you can still have a bad diode in the alt. the diode could be the charging problem and it could also kill the VR you jsut put in there. the alt could be good and you have a bad battery, or maybe just a bad conection.
thats why you take it to someone that can test the entire thing and either fix what is needed and be done with it or tell you what is wrong.

now you have a bunch of guys telling you 12.3 is good, 12.3 is bad and what ever. you can either put another VR in it since you doubt that one you have, and maybe the alt will kill it or it may fix it. if not you will end up taking it to someone, and there is nothing wrong with that.

if you really want to learn. open it up to get to the diodes and check the diodes to see if they are good. then you need to get another diode and solder it in if it is bad. then what about the bearings. might as well replace those while you are in there.

if you dont think i am a do it yourself guy, look up my thread on rebuilding the starter.
there is one thing i have learned over the years, maybe i dont always follow it, is work smarter, not harder. at least let someone that will do it for free tell you whats wrong, just to be sure. then do your checks and remember what you saw goes along with what you were told is wrong.

[Joe Bob]

He's getting 12.3 at idle with all accessories running. The next test for the DIYer is to run the idle up with the meter.

He hasn't done that. His idjut light is functional at the self test prior to startup and does not come on during driving.

Checking the other suggested items, while a good idea, is a bit premature.

[Ronnie's.930]

Well, my concerns were a false alarm - I was able to set the meter up on a bench so I could see it while operating the throttle . . . 2K + RPM = 13.2v +/-, no accessories running and engine at operating temp; 12.5v +/- with headlight, foglights, a/c (including extra fender condenser with fan). It looks like the charging system is fine. I don't know why I didn't do the higher rpm test in the first place, as I have known for 30+ years that this is what should be done - guess I needed a reminder. Sorry for the needless hassle.

[Joe Bob]

I don't see a problem with your concerns. Maybe this thread will help someone else down the road.

Glad you figured it out.