Electrical problem 940

[TonyS9]

Sorry, I see you did report the voltages but not the conditions.

If you have 13.85V at the battey at idle and 14V at the alternator, its good result having 0.15V drop from alternator to battery, but you need to check under higher load say with the lights on high beam. The difference should not be more than 0.3V under high beam (and engine running) but it will just take progressively longer to charge the bigger the difference. Mine was at 13V and it was still "working" but charging at half the rate.

If the earth strap (or any other connections) has resistance this test will show it up. Usually it will be a bit low at idle, but you can rev to say 1500 to get a better reading.

When you say you don't think it charges below 3000rpm, have you checked the battery voltage at idle? And what about the voltage before and after switching on the lights?

[Ammorack]

Originally Posted by TonyS9

Sorry, I see you did report the voltages but not the conditions.

If you have 13.85V at the battey at idle and 14V at the alternator, its good result having 0.15V drop from alternator to battery, but you need to check under higher load say with the lights on high beam. The difference should not be more than 0.3V under high beam (and engine running) but it will just take progressively longer to charge the bigger the difference. Mine was at 13V and it was still "working" but charging at half the rate.

If the earth strap (or any other connections) has resistance this test will show it up. Usually it will be a bit low at idle, but you can rev to say 1500 to get a better reading.

When you say you don't think it charges below 3000rpm, have you checked the battery voltage at idle? And what about the voltage before and after switching on the lights?

12v with light on. 13,9 with evetything off
The Engine struggles to rev. Litteraly.
I changed that blue lead from alternator to ground.
I changed the battery ground cable.
I checked tps valve and adjustment just to be sure.
It’s 0.3 v from alternator positive to battery positive.

I’m going to the junkyard with this car soon. It won’t run properly. It’s killing me.

What’s new
Leads, plugs, distributor, rotor, distributor cap, ICV, ECU and EZK, coil, Cranksensor, fuel pump, fuel filter. Gasket on Intakemanifold and TPS, lambda,
battery. Knock sensor, timingbelt, it’s timed correctly

[Ammorack]

Originally Posted by 360beast

Do you mean when you turn the headlights on?

Sounds alternator related to me

I mean when I turn my headlights ON. The rpm is more stable with load on. I had to drive with heater on rear window and heater fan on max to have stable rpm. But now my rpm is everywhere and it’s backfiring and too rich and lean mixture

[Laird Scooby]

You have a serious problem there that you're unlikely to find by yourself, even with our help.

Why did you mess about with the TPS? It's nothing to do with the charging system, neither is anything else you've changed but you don't seem to have changed the alternator?

First of all, do you get the charge warning light when you first turn the ignition key to position 2 without starting it?

[Ammorack]

Originally Posted by Laird Scooby

You have a serious problem there that you're unlikely to find by yourself, even with our help.

Why did you mess about with the TPS? It's nothing to do with the charging system, neither is anything else you've changed but you don't seem to have changed the alternator?

First of all, do you get the charge warning light when you first turn the ignition key to position 2 without starting it?

I do get the charge warning light on KPII
I tested another alternator from a 940. It made the engine worse. It wouldn’t rev past a certain limit. I knew that answer would come. This nut is hard to crack.

[Laird Scooby]

Is that certain limit about 3000rpm and when it gets there, does it die and then rev up again?

[aardvarkash10]

change the exhaust pipe.

Its as logical as what's happened so far.

[taiwan740]

Feels like a grounding issue, probably a cable breaking down somewhere, or battery connections.

I'm gonna science and say there's some lead that's barely making a connection, but given extra load the pixies have more energy to leap across the Chasm of Despair (a break in the cable) therefore you get slightly better performance.

It's something simple, but it's hiding. Also don't scrap, there's always some sucker on here (me) that buys junk and calls it a 'laff'

[TonyS9]

With the lights on what is the voltage at the Alternator?

(across the alternator, not from chassis to alternator +)

[Laird Scooby]

Originally Posted by TonyS9

With the lights on what is the voltage at the Alternator?

(across the alternator, not from chassis to alternator +)

12V apparently Tony, it's hidden somewhere further up.