Alternator or Voltage Regulator??

[CJP5]

I've been experiencing some surges in my AC fan speed and brightness changes in my headlights at night. Pg 270-14 in the Bentley manual gives directions for checking the Alternator and the Voltage Regulator, along with a test to determine which is faulty.

The voltage at the battery with everything turned off is 13.86, almost identical to the pictured voltage.

Once I turn on the stereo, AC, blower fan and lights the voltage rose to over 16 in a steady climb from 13.86 The Bentley manual says that voltage that is the same as before everything is turned on indicates a VR issue. Reading lower points to Alt. But nothing stated for HIGHER voltage... ideas? I dont want to spend the $$ replacing the alt if it is just the VR.

[86 911 Targa]

Originally Posted by CJP5

I've been experiencing some surges in my AC fan speed and brightness changes in my headlights at night. Pg 270-14 in the Bentley manual gives directions for checking the Alternator and the Voltage Regulator, along with a test to determine which is faulty.

The voltage at the battery with everything turned off is 13.86, almost identical to the pictured voltage.

Once I turn on the stereo, AC, blower fan and lights the voltage rose to over 16 in a steady climb from 13.86 The Bentley manual says that voltage that is the same as before everything is turned on indicates a VR issue. Reading lower points to Alt. But nothing stated for HIGHER voltage... ideas? I dont want to spend the $$ replacing the alt if it is just the VR.

A test of your charging system will pinpoint the issue.

The charging voltage should not exceed 14.5V

Also, I would not drive the car, as excessive charging voltage
can damage your battery as well as other components such as your DME.

Most likely a VR issue.

You may pm me as needed.

Good luck,

Gerry

[ivangene]

what year car? - I vote VR too, just went down that road....and once I saw the voltage I stopped driving immediately till fixed....

in my case I had boiled the battery too...pop off the caps and see what the level is and look for white powder in the area... pull the battery out and douche the entire area in a battery acid neutralizer....top off the battery and make sure there is a vent tube in place if needed.

new VR and I have been good to go since

[ivangene]

reason I ask what year is post 84' IIRC has built in VR to alt

[CJP5]

It's an '88. Battery is clean.

[Driver_X]

Buy one of those volt meters you stick in the lighter. Drive around a bit an report back voltage @ idle & 3,000 rpm. If it's over 14.5 @, assume it's the VR and it's time for a new/rebuilt alternator. You could also do the same tests at the battery using a multimeter and a helper.

[CJP5]

Originally Posted by Driver_X

Buy one of those volt meters you stick in the lighter. Drive around a bit an report back voltage @ idle & 3,000 rpm. If it's over 14.5 @, assume it's the VR and it's time for a new/rebuilt alternator. You could also do the same tests at the battery using a multimeter and a helper.

That's no different than the test I've already done at the battery with the multimeter per the Bentley manual. I'm just going to replace the alt and be done with it.

[ivangene]

are you planning to buy a VR and swap it off the back of your ALT?

FWIW I searched around and found one of those "starter/alternator rebuild" places. after a phone call i realized this guy was "old school" and took my unit to him for complete rebuild. Comes with a 1 year warranty and cost <$100 total...

I ran the gamble and so far so good - plus the whole thing was done at once

[CJP5]

Just got the Alt out of the car and the yellow wire to the VR is burnt. Could replace just the VR, but I don't want to do this job again for a long time, so I think the reman BOSCH at $262 is a better way to go.

Thanks for all the help!

[CJP5]

Completed the re-install of the new alternator last night. While I had everything out I had the fan, cove and outer pulley media blasted. Looked pretty bad before, blasting made a big improvement. I thought about powder coating, but decided to go with high heat enamel. Big improvement!

[CJP5]

[Flat Six]

Originally Posted by CJP5

Nice. I always liked the red fan detail; too bad it also can be confused w/a Motor Meister "rebuild" . . .