Buying 92, 525i But weird electrical problem. Ideas?

[Exnilo]

Hello all. I need some help here. I am purchasing a 1992 525i Auto. Low kms (120). It seems to have 2 problems. 1 is the steering box needs adjusting (no problem) and 2 a very weird electrical thing. Ill explain: I was driving the car and noticed that the head lights kept going brighter then dim, brighter then dim. When this happened the Check engine light also cam on. I tried the interior lights and they also went up and down with the headlights. I then changed the auto trans shift button and suddenly it went into limp mode (trans program). I stopped shut the car down, waited a minute and the tranny came back online but the lights still did the weird up and down. Nothing else seems affected. Every thing seems to work fine. Ideas? Thank you in advance.

[billb]

Hello all. I need some help here. I am purchasing a 1992 525i Auto. Low kms (120). It seems to have 2 problems. 1 is the steering box needs adjusting (no problem) and 2 a very weird electrical thing. Ill explain: I was driving the car and noticed that the head lights kept going brighter then dim, brighter then dim. When this happened the Check engine light also cam on. I tried the interior lights and they also went up and down with the headlights. I then changed the auto trans shift button and suddenly it went into limp mode (trans program). I stopped shut the car down, waited a minute and the tranny came back online but the lights still did the weird up and down. Nothing else seems affected. Every thing seems to work fine. Ideas? Thank you in advance.

low battery voltage will give TRANS PROGRAM and CHECK ENGINE lights too.

[BobHarris]

I agree, I had the fluctuating lights problem on my 518, that turned out to be the unit on the back of the alternator.

All the best

Bob

[tye1138]

I agree, I had the fluctuating lights problem on my 518, that turned out to be the unit on the back of the alternator.

All the best

Bob

Yep, BUT I had no luck replacing my resistor/capacitor pack on the back of the alternator. I ended up having to replace the entire alternator. Thats kinda interesting the check engine light went on, I've not seen that before with low voltage on my 525 wagon!

BTW, get a BOSCH instead of the stock replacement. I put a 85 amp BOSCH replacement alternator in my 328i and I never had another problem!

[Javier]

from battery and from alternator.

Javier

[pyro]

haha the car i bought that iv had the engine trubles with (m50 won't start) thread... i thought i could fix it easy... boy was i wrong but however your problem seems alot easyer to fix than mine

[upallnight]

How old is the battery, could be the battery has a dead cell. Bring it into Pep girl and they will check the battery for FREE.

[Exnilo]

Thanks to all for the help. I will try all of those things. Really appreciate the feedback from all. Thanks!

[Exnilo]

Thanks to all. The problem was the battery. The car was still using its original. We replaced it and the regulator on the alternator just to be safe. Now? PUUURFECT! Thanks guys.

[uscharalph]

Thanks to all. The problem was the battery. The car was still using its original. We replaced it and the regulator on the alternator just to be safe. Now? PUUURFECT! Thanks guys.
Congrats! I love simple fixes!