Electrical problem 940

[Ammorack]

Lately my 1994 940 B230fd got problems with the electricity or something like that. When I turn off headlights, the engine starts to go rough and doesn't like it. So is the heater for rear window.

Whatever it is. It’s driving me crazy.

[360beast]

Do you mean when you turn the headlights on?

Sounds alternator related to me

[mocambique-amazone]

Originally Posted by Ammorack

Lately my 1994 940 B230fd got problems with the electricity or something like that. When I turn off headlights, the engine starts to go rough and doesn't like it. If this apears only for a short time, 1-2 seconds, and the engine will run later "normal" you shouldn't take care about this. Standart at a sensible running engine. If everything is ok Volvo 740/940 have a "tick" to do this So is the heater for rear window.

Whatever it is. It’s driving me crazy.

jump in Voltage, stop beeing crazy

good luck, Kay

[Ammorack]

Originally Posted by mocambique-amazone

jump in Voltage, stop beeing crazy

good luck, Kay

Could it be the cable from alternator to battery? Or groundingpoints? Alternator regulator are new. Battery is 13,85v, alternator 14v
Battery 12,8v without ignition.

[Laird Scooby]

Originally Posted by Ammorack

Could it be the cable from alternator to battery? Or groundingpoints? Alternator regulator are new. Battery is 13,85v, alternator 14v
Battery 12,8v without ignition.

Check the alternator earth strap, these often fail, even if it looks alright. You'll probably find the missing 0.15V between the alternator casing and the engine block with your voltmeter, indicating the earth strap is failed/failing.

[Ammorack]

Originally Posted by Laird Scooby

Check the alternator earth strap, these often fail, even if it looks alright. You'll probably find the missing 0.15V between the alternator casing and the engine block with your voltmeter, indicating the earth strap is failed/failing.

The problem is that I don’t find the ground for engine.

[Laird Scooby]

Originally Posted by Ammorack

The problem is that I don’t find the ground for engine.

It's usually on or near the starter motor.

You need to check the alternator earth strap first. You know where the alternator is, the earth strap will be between the alternator case and the alternator bracket on the engine.

Do that first and worry about the engine earth later, it's obviously not that bad as it starts, which it wouldn't if the engine earth was poor.

[Ammorack]

Originally Posted by Laird Scooby

It's usually on or near the starter motor.

You need to check the alternator earth strap first. You know where the alternator is, the earth strap will be between the alternator case and the alternator bracket on the engine.

Do that first and worry about the engine earth later, it's obviously not that bad as it starts, which it wouldn't if the engine earth was poor.

That blue lead from the alternator. That grounding there. I have cleaned where the lead contact the block.

I have had this issue for some months now, and I can’t find the solution.

It feels like the alternator charge after 3000rpm and under that it almost stalls

[aardvarkash10]

then take it to someone who knows what they are doing.

[Ammorack]

Originally Posted by aardvarkash10

then take it to someone who knows what they are doing.

I’m here to find help and support. And hopefully someone is kind enough to do so. Not to be harassed.