Alternator Light comes on when accelerating

[radiantgal]

Hi,

I have a 1998 S70.

I was in the mountains last week where the temp was freezing or below.

Since I have come home the alternator light comes on when accelerating
from a stop and then and goes off after about 5 seconds when I step on
the gas.

My mechanic said battery and the alternator tested ok. He works mostly
on BMW's
these days, however started his business working on Volvo's.

Should I be concerned?

Any suggestions?

Thanks,
Radiant Gal in California

 

[zencraps]

The most logical thing would be to look for a loose or glazed drive
belt.

 

[Peter K L Milnes]

The onlky thing I can think of is that the alternator drive belt must be
slightly under-tensioned. That is looser than it should be!

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

 

[Michael Pardee]

The onlky thing I can think of is that the alternator drive belt must be
slightly under-tensioned. That is looser than it should be!

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

BTW - a good "shadetree" test for a slipping belt is to try to turn the
alternator by pushing on a cooling vane (right behind the pulley) with a
thumb. If the alternator moves (and the belt does not) the belt is either
too loose or worn out.

Mike

 

[Michael Pardee]

Hi,

I have a 1998 S70.

I was in the mountains last week where the temp was freezing or below.

Since I have come home the alternator light comes on when accelerating
from a stop and then and goes off after about 5 seconds when I step on
the gas.

My mechanic said battery and the alternator tested ok. He works mostly
on BMW's
these days, however started his business working on Volvo's.

Should I be concerned?

Any suggestions?

Thanks,
Radiant Gal in California

Besides the belt concern, it's possible the engine ground is bad and the
engine is getting a stray ground until you make it work and torque to one
side. The ground is a braided strap under the car in the older models but I
don't know what it is in the S70.

Mike

 

[User]

Hi,

I have a 1998 S70.

I was in the mountains last week where the temp was freezing or below.

Since I have come home the alternator light comes on when accelerating
from a stop and then and goes off after about 5 seconds when I step on
the gas.

My mechanic said battery and the alternator tested ok. He works mostly
on BMW's
these days, however started his business working on Volvo's.

Should I be concerned?

Any suggestions?

Thanks,
Radiant Gal in California

I'd guess that the d+/61 wire on the alternator is chafing/chafed
somwhere and that when the motor rotates under starting load it shorts
to ground and causes the light to come on.

Bob

 

[Guest]

I'd guess that the d+/61 wire on the alternator is chafing/chafed
somwhere and that when the motor rotates under starting load it shorts
to ground and causes the light to come on.

Bob

Although Bob is probably correct --- in a Porsche I own the flicker
and intermittent light on acceleration was finally diagnosed as being
a screwed up 'diode block' (or the solid state equivalent) --- the
alternator was occasionally dribbling out some AC current.

It might be something to check on after you're sure that the chafed
wire isn't the culprit, ( --- AC can fry the engine mgmt system).