alternator over charge question

[steveo3002]

my old polo is over charging , meter swings between 12 and 16 volts with no relation to engine speed

i swapped over a new voltage reg with brushes and its still just the same

is the other internal bits n bobs that would still make it overcharge ?

 

[rtbcomp]

Make sure the connections are tight, including the earth. If it has an external sense connection make sure this is in good order.

 

[steveo3002]

have done mate cheers

 

[rtbcomp]

What state are the slip rings in? A bad connection between the slip rings and armature could give this fault.

 

[steveo3002]

looks normal to my untrained eye

 

[Fazerruss]

my old polo is over charging , meter swings between 12 and 16 volts with no relation to engine speed

i swapped over a new voltage reg with brushes and its still just the same

is the other internal bits n bobs that would still make it overcharge ?

Are you sure you changed the regulator and not just the rectifier?
Some alternators do not have an on board regulator.

 

[steveo3002]

yes i am

 

[rtbcomp]

Are you using a multimeter or does the car have a voltmeter fitted? If it's a fitted VM it may be interesting to compare it with a multimeter.

Where are you measuring the voltage, at the alternator or battery?

Do you get any other symptoms, such as gassing battery, blown bulbs &c?

 

[steveo3002]

ive measured it several places and yes the elecs are speeding up /slowing down with the charge rate

 

[The_Yellow_Ardvark]

Check your meter against another known good source.

I watched someone chase a fault down, as his meter was giving wring reason.

Polo.
Check engine to earth (body)
Check battery.
Top up and trickle charge.

With a good meter.
1, Check battery. Neg. on a good body earth. Pos. on battery.
Meter should read between 12.4 and 12.9 Volts

2. Start car. let idle for a few minutes. Meter should read 13.3 to 13.9 volts

3. raise engine RPM. volts should not go over 14.5v.

4. Switch on all elec. loads. Volts will drop, but no lower than 12.3 Volts.
4A. raise engines rev. It will rise to approx.. 13.7 volts.

If the above is ok, the Alt. is ok. battery may be at fault.

 

[The_Yellow_Ardvark]

EDIT TO ABOVE.
Battery to body should be less than 0.2Ohm.
Please take into account meter resistance.

 

[steveo3002]

the heater fan is going beserk to match when the meter reads 15+ volts , ive used 2 meters and checked all the wires

it blew both dip beams about 3 weeks and ive been driving around with the multimeter on checking it , was all in check until yesterday so that explains the bulbs

 

[Johnseat]

How old is the car, some manufacturers control the alternator voltage output via an ecu but if the sensing wire breaks then the alternator switches over to a self exciting type which requires a blip of yhe throttle to start the charging.

Try and get a hold of the wiring diagram for the charging circuit.

 

[mr migwire]

replace the alternator would be my advice, not to expensive iirc.

 

[steveo3002]

its a 1988 car so no fancy ecu

yes i will try another alternator and see how it goes , good excuse to upgrade to a slightly bigger one

 

[Johnseat]

Upgrade time then, look on the vw forums as you may be able to upgrade the alternator to a newer vw model charging system.

I had a 1990 mk2 golf and the best I did for it was to put the mk3 golf gti alternator and brackets onto my 16v engine.
It removed the single V belt and changed it to you multi rub belt which is way better.

 

[steveo3002]

yep 90a golf derv fits with minimal effort- no room for ribbed belts on a polo