I have a 1989 300 E which has a small, yet annoying problem...when I open the drivers door the interior light occasionally blinks at a steady rate/pattern...almost like I am doing something wrong and the car is telling me to stop whatever I am doing.

I replaced the door switch thinking that was the problem...nope still does it!

Thanks for your replies!

 

Two possibilities come to mind: Bad ground conection on strap from frame to bell housing. Failed diodes in alternator.

 

Have same issue, continues without ground or diodes being at fault. Please report your outcome.

Hineywineries! When did Thor and Red Hiney relocate from beautiful downtown Chester, PA?

 

I didn't know that Big Red and Thor Hinney were ever in Pa. They had a small winnery here locally in beautiful American Canyon which they operated with the help of their sister Ophelia Hinney. They were actually my brothers and sister on my mother's side. I eventually bought them out.

 

I ran this past my colleague today and explained the symptoms. He is extremely good at diagnostics, and he came to the same conclusion that I did. It would either be a loose ground strap at the bell housing or dad diodes in the alternator. Now this is assuming that the engine is running when the problem occurs. If the problem occurs in the key off position, then that's another story. Was the engine running or not?

 

OK...I have discovered that when the interior light pulses (or strobes) if I accelarate the car it stops pulsing. That would lead me to believe it is a ground problem...? If so...where would I look to fix (clean) the ground.

Would the right driving light going out almost immediately after a new bulb being put in be related to the interior light problem? Perhaps it was a bad bulb....

Thanks in advance!

1989 300E
2002 Jag XK8 Coupe

 

MB69,

I answered your first question in post number two. The chassis to engine ground is provided by a strap from the frame to the transmission bell housing.

I doubt that you installed a defective driving light. If you had a short at that point, the fuse for that circuit would have blown.I think what actually happened is you are dealing with a high intensity bulb. You cannot touch these with your bare hands during installation, because that will cause them to grenade instantly. If you do accidentally touch the glass part of these bulbs during installation, you can clean it with some alcohol. Common theory is that the oil from your hands creates high heat at that point on the glass. This is not true. The reason the bulb burns out is the because the oil stain reflects heat back within the bulb. The bulb sort of supernovas.

 

I had this problem last year and I replaced my voltage regulator which screws in the back of your alternator and the problem was fixed. These brushes on your regulator could be worn out. Got a Bosch one for 70 bucks.

 

mw124,
I don't think you had a pulsating light problem. You had a no charge condition. In 30 years as a professional MB mechanic, I have never seen the symptoms you claim.

 

hiney well now u have i guess had the exact same problem cuz i bought a piece of crap alternator then before i did anything else i bought a Bosch voltage regulator and problem gone.

 

Sorry but I have never experienced that problem, because I don't buy piece of crap alternators. An old adage says that you get what you pay for, and in most cases that is true. If you insist on buying a $70.00 alternator from Crapazone, you must consider how many people are involved before it gets to you. The jobber must make $10.00. The wholesaler must get $10.00. The distributer must get $10.00. Crapazone corp. must get $10.00. THe franchised retailer must $10.00. The rebuild guy has to make $10.00 to stay in business.This means he can only spend $10.00 to rebuild the unit. It's a numbers game. Most units will fail, but enough will work well enough to turn a profit. Guess who spends his days off changing parts til he finds one that works for now?

 

the regulator was 70 not the alternator lol. Uve really never heard of this and uve been a mechanic for 30 YEARS?? geez. well good luck anyway MB69 i just told u what my prob was and a few other ppl with similar symptoms have fixed it with a simple voltage regulator change, happens all the time.

 

I still maintain that I have never seen that symptom in the professional world using good quality parts. Once a guy brought a master cylinder to me that he bought at NAPA auto parts. Against my better judgment I installed it while reminding him that if it was defective he would be required to pay the labor twice. The master cyl failed before it left the shop. In another case a friend called and said his 300 SD wouldn't start. I don't normally make house calls, but because he was a friend, I made an exception.After determining that his battery was fine, I smacked the starter with a small hammer. It is common to get a few more starts this way when the brushes are worn out. He told me that his wife worked in the warehouse at AutoZone and could get a rebuilt at wholesale. I advised him that it probably wouldn't last very long. He brought me the starter and I installed it. Less than a week later he called again saying the car would not start.He could not see that it was a starter problem twice in a row and bought a new battery. The car still would not start. Since he was a friend I went to his workplace again and smacked on the newly rebuilt starter with a little hammer. The car started fine. Although the price was several times more, he said to go ahead and order a Bosch rebuilt. That was several years ago. No problemo since.The point is that cheap parts are pretty much worth what you pay for them.