Andy_M

A couple of weeks ago while sitting in the car while it had been idleing for a while I noticed all the warning indicators start to glow, at first dimly then full on. I tapped on the accelerator and the lights went out and never came back on. This happened one other time about two weeks before that under the same circumstances.

Last night my wife had the car out on an errand about 40 mins away. On the way home, she noticed the ABS and SRS indicators about half way lit up, then they faded back off. Then, 4 or 5 miles later, the dash lights slowly started to dim. They kept dimming out slowly until they were almost off. The headlights had also dimmed. Then the car started to run rough. She feathered the gas and the car came back to life, the lights went back on full, and the car was fine. Maybe 5 mins later it did this again, then 2 or 3 mins later it repeated the process, but this time it went dead about a mile from home. She called and said it was absolutely dead. She had interior lights but got nothing if she turned the key. I went to where she was, took out the jumper cables, and asked her to try the key again. It turned over but would not start. I jump started the car and drove it home. It was fine.

Obviously the battery has been drained, but does it also sound like the alternator needs replacing ?

RobertG

It sound like the alternator is going on you and I wouldnt rule out the battery either.
jump start it and let it run then check the voltage at the battery if it's under 13 volts then your alternator is dead and the car is draining your battery.
If you have readings of 13.5 or higher then you might need a battery .
Optimum voltage with the engine running should be 14.7 volts.
If you dont have a volt meter (dvom)then take it to a repair shop.

ZorroAMG

Since the Alternator sounds like it is on its way out, it would also have wreaked havoc on the battery. I would do both for sure now.

shdoug

It's probably just the alternator, but if your battery is a couple years old and NOT an MB battery, I would change it also. What happened should not have hurt the battery unless it became overcharged, but it sounds like it was the opposite scenario. If it is an MB battery, I would keep it until it is at least 4-5 years old.

That's just me- I'm frugal.

Andy_M

Thanks all. That is pretty much the way I read it, but never hurts to get some other opinions. I picked up a new battery and they'll have the alternator in the morning.


Thanks everyone....

myfirstbenz

I would put money on the table that it is a voltage regulator and not the alternator. This part is less than $30 and can be changed out in less than 5 min. It is on the back of the alternator and requires 2 phillips screws to remove. Pull yours out and I bet the brushes will be warn out. I had the exact same problem... it is not uncommon for these cars to do this, but it is uncommon that the alternator is bad.

shdoug

^ I'll bet he's right.

jharrisiii

Had somethnig similar happen. Called a friend who called his mechanic while I was sitting on the side of the road waiting for a tow. Mechanic nailed it with the voltage reg. Took out the old one and immediately saw the problem: dead brushes. Cleaned up the area, swapped in the new regulator and all was OK. Definitely the regulator.

GEDaggett

Often times when your alternator goes out it is a slow process and your battery will be over worked. If the alternator isn't putting out enough voltage to operate the cars electrical at with accessories on then it will start to drain the battery and later recharge it when driving in the day time when less accessories are needed. This process of constant influx of charge will trash the battery. Depending on how long the Alternator has been weak and the age of your battery you should keep a close eye on it because it will most likely have a very short life.

velvet fog

Agree with myfirstbenz. I've had the same symptoms on other cars and it turned out to be the voltage regulator. Also, if you are going to just start replacing parts until the problem goes away, why not start with the cheapest parts first? Good Luck.

Andy_M

Well guys, I wouldn't want to say it wasn't the voltage regulator at the heart of the matter, but I went ahead and replaced the alternator and the battery. When I removed the old alternator I could move the shaft around like a round peg in a square hole, so I think it was most definitely "tired".

Took me a while to figure out that life is a whole lot easier if you remove the fan shroud, but at least I eventually figured that one out for future reference. I'm a little concerned about the pulley bolt being tight enough. I didn't have access to an impact wrench and couldn't really get the torque wrench on the bolt to see if it was anywhere near the 75 ft/lbs specified. (I'm still *****ing about spending almost $200 for an alternator and it doesn't even have a new friggin pulley on it...) All I could do was use a heavy 1/2" drive wratchet with a 22mm socket and locked it down as tight as I could, then gave it an extry pop or two with the mallet for good measure.

During the process I found out that my belt tension adjuster doesn't appear to move. All turning it did was push on the plate, so I guess that needs replacing unless there is a locking bolt that I missed on it somewhere.

Off to change the fuel filter next. She's bucking ever so slightly when your maintaining a steady speed. Doesn't do it under acceleration, just when your maintaining a steady speed. Other than that she runs fine.

GEDaggett

[QUOTE=Andy_M;2714966]Well guys, I wouldn't want to say it wasn't the voltage regulator at the heart of the matter, but I went ahead and replaced the alternator and the battery. When I removed the old alternator I could move the shaft around like a round peg in a square hole, so I think it was most definitely "tired".


During the process I found out that my belt tension adjuster doesn't appear to move. All turning it did was push on the plate, so I guess that needs replacing unless there is a locking bolt that I missed on it somewhere.

Hey with that belt tensioner there is an anoying little adjustment peice on there that is very easy to strip out. The good thing is you can get it at the dealership for $27.00 (just for te adjustment rod) maybe that will solve your problem. I had a simaler issue and it was that the stud was stripped a good 1/2 inch down.

shdoug

I would suspect the O2 sensor, not the fuel filter. If the fuel filter was that plugged, it would hardly accelerate at all.

Andy_M

It seems to be rapidly getting worse now. Very lethargic, and not smooth, acceleration. Sort of a bucking at steady speed. Poor power unless you kick it down and floor it. No CEL though.

Thinking back, this has been coming on for a week or more. I recall thinking the economy gage was hitting the red more than it should last week coming home one night. I just wrote it off to it being very windy out that night. Also, I recall my daughter following me one time - a while ago - and saying that it smelled rich driving behind it.

Still sound like the O2 sensor is more likely ?

I recall reading that a 1990 Mustang 5.0L sensor is the same sensor but a lot cheaper, but I have seen 2 different Bosche part numbers mentioned for that sensor 13942 and 13953. There is also a universal version of that same Bosche sensor P/N 15725 that looks to be the same sensor without an end of any kind on it. Anyone know which is correct ?

Andy_M

All,

I'm going to close this thread and open up one dealing with this rough running/bucking problem specificly. I may get more responses that way. Thanks for your help with the batt/alt.

Andy_M

Just as a final update.....I replaced the coil yesterday and the issue seems to be gone. Not sure if this ties back to the alternator issue or not, but the coil change seems to have done the trick.