318is check engine electrical II (voltage too high?0

[newscam]

This is my original post:

I have a 92 318is with the check engine light coming on. It comes on at speed on the highway and when I reve the engine it goes off. I punched the gas pedal 5 times while holding down the odometer button and got the trouble code 1231. I did an internet serch and found this means battery voltage low. My battery is good. Any ideas? Could it be a bad alternator or voltage regulator. Another symptom is my head lights. They pulse when I am standing still at stop lights. Any help in this diagnosis would be greatly appreciated!!

Thanx--newscam


Fun to drive gave me this great advice:

You need to measure a few things. Measure the voltage at idle going into the battery. Measure the voltage at a fast idle 2000 rpms.
They way most regulators work is once you start the car the regulator will gradually ramp up to around 14.5 V max to 13.7V min values.
If you are not getting at least 12.6-7V at idle once the car has been idling a while and your 2000 rpm measure is low too then most likely you have a bad voltage regulator.
good news is that the regulator is on the back of the alternator on the left side standing behind the alternator looking forward.
I am fairly sure it is a Bosch part so you should be able to replace this assuming the alternator is good.




I did this test and got 14.9-15.1v at both the low idle and faster idle speeds. The voltage remained pretty much constant at both speeds and in between. Is this voltage too high? My Chilton manual says this is out of spec and I should replace the alternator.

I also did another test from my Chilton manual. I started the car and looked for the battery light to come on momentarily then shut off. It did not. The manual said this was indicative of a bad voltage regulator or alternator. The test does not seem very scientific to me.

Any advice would be great. I am not averse to buying and intalling a new alternator. I just want to make sure this is my problem before shelling out the big bucks for a BMW Bosch style alternator.

Any advice would be greatly appreciated,

newscam

[fun2drive]

Your voltage is way too high and you better check your battery as you will boil the acid out of it if the voltage stays that high.
One thing I would suggest to verify that the VR is bad is to go to a place like Autozone and ask them to put your battery under load while measuring the voltage.
If the battery comes off good then no doubt you have a bad VR.
I can't understand your lights flickering however.
Hope this helps some...

[newscam]

Thanks again fun2drive. I'm gonna get a new or good used vr and swap it out to see if that solves the problem. Thanks,

newscam

[IgorZ]

Hey man,

I have 325ic 1990 and I have got exactly same problem.
The car is running just fine and I was waiting for warmer weather to fix this problem.

One more symptom: Everytime the check engine light is on all the lights on dashboard are brighter and if fan or rear window heater is on , they will make louder sound.

I guess my problem is VR.

What did you find out about your car?
was it vr ir alternator?