Weird electrical problem ruined my car!

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LFY
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Weird electrical problem ruined my car!

Post by LFY » 24 Nov 2018, 16:11

Hello everyone,

1 month ago my car (406 1.8 16V LFY) had a charging system issue. The alternator didn't charge the battery and the battery warning light stayed on.
The alternator diagnosed as faulty. The repairman told me that the Brushes are worn but you must replace the whole voltage regulator as a whole and not just the brushes.

The original alternator on the car was made by Bosch and I searched a lot to find a used voltage regulator with solid brushes. He fitted the voltage regulator and fitted the alternator on the car.

I thought the problem was solved but it was just the beginning of trouble! My car had been sit unused for about 2 weeks and when I wanted to start the engine the battery was weak. I jump-started my car but after 5 minutes the engine died. I turned it on and increased the throttle a bit (about 2000 RPM) and the engine stayed on. I tested the battery voltage with the engine running and it was 17.2 volts!!!! I took the car for a spin and it dropped to 14.9 volts! Still too high. The car didn't behave normally as well! The engine has a fast idle (about 1500 rpm). I don't know what it has to do with charging system!

Today when I started the car the battery warning light appeared again and battery voltage was 12.3 (no charging!). I shut off the engine and started it again and the voltage was 17.2 volts and the idle was about 2000 RPM! Sometimes the idle dropped to 800 and the car behaved normally but soon the fast idle would return!

It is driving me crazy! I don't know why these things happen! Maybe the voltage regulator is faulty but what does it have to do with fast idle?!

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Re: Weird electrical problem ruined my car!

Post by LFY » 24 Nov 2018, 20:31

Can a faulty voltage regulator increase idle speed?

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Re: Weird electrical problem ruined my car!

Post by xantia_v6 » 24 Nov 2018, 21:23

Not directly, but it can damage ECUs and other electronic devices.

Vehicle electronics are generally designed to withstand 16V continuously, 24V for a few seconds (perhaps shutting down some normal functions) and 50V for a few tens of milliseconds. Beyond that it is down to the conservative nature of the design and luck as to whether damage is done.

Prolonged operation at excessive voltage is also likely to result in battery explosion due to the production of hydrogen gas.

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Re: Weird electrical problem ruined my car!

Post by white exec » 25 Nov 2018, 00:05

Excess voltage can result in shut-down of some ECU functions. If you're lucky, removing the excess voltage (eg by disconnecting a faulty alternator, so the car runs solely on the battery) might allow normal running. Worth a try.

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Re: Weird electrical problem ruined my car!

Post by LFY » 25 Nov 2018, 08:10

So, it has damaged ECU and sensors. I don't have the money to replace them. What a disaster! :(

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Re: Weird electrical problem ruined my car!

Post by xantia_v6 » 25 Nov 2018, 08:53

I would suggest that you try taking off the alternator drive belt and see if the engine runs properly. If it does, then you may be lucky and just need a replacement alternator.

Note that it is not recommended to run the engine with the belt on and alternator electrically disconnected, as that is likely to cause further damage to the aternator (due the potentially high voltages generated).

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Re: Weird electrical problem ruined my car!

Post by white exec » 25 Nov 2018, 09:34

I had meant to say disconnect the inputs to the alternator (which should switch off its output) - but thanks for adding that caution, Mike, and the better tactic of just removing the belt.

" So, it has damaged ECU and sensors . . . "
Do try the suggested test first, though.

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Re: Weird electrical problem ruined my car!

Post by LFY » 25 Nov 2018, 10:10

Thanks a lot for your help.
But if I remove the drive belt, I can't go for a spin to see how the car behaves because it will damage the hydraulic steering system to function without the pump boost.

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Re: Weird electrical problem ruined my car!

Post by white exec » 25 Nov 2018, 10:32

Then disconnect/unplug all the cables from the alternator and leave the belt in position.
Use some tape on any bare-ended ones (especially the main cable going to the battery) to prevent accidental shorting.

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Re: Weird electrical problem ruined my car!

Post by LFY » 25 Nov 2018, 10:37

If you think driving without drive belt will not damage the steering system, I will do it.

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Re: Weird electrical problem ruined my car!

Post by white exec » 25 Nov 2018, 10:39

If the alternator belt also drives the power steering pump (and anything else vital, like water-pump), then leave the belt in place.
For safe driving, you will need power assistance for the steering.

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Re: Weird electrical problem ruined my car!

Post by LFY » 25 Nov 2018, 10:50

So, I should remove the whole intake manifold to be able to disconnect alternator wiring!
I did it 2 days ago. It requires 2 hours of work.

Tight area of working with the manifold in its place!

The water pump is driven by timing belt not the drive belt. The drive belt only drive the alternator and power steering system.

But if the streets are not crowded, I think it is possible to drive without the power steering boost.

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Re: Weird electrical problem ruined my car!

Post by white exec » 25 Nov 2018, 10:56

OK, didn't know dismantling would be necessary to get to the alt. connections.

I don't have a circuit diagram to hand for the car, but if there is an ALT FUSE (alternator fuse), it might be possible just to remove this, in order to prevent the alternator from outputting. (Alternators need an input - which is usually via IGN switch, and often a fuse - in order to operate and produce output.)

Maybe someone here can help with a circuit diagram.
Your Owner's Handbook might also list a Fuse for the alternator.

You'll likely know that the alt. isn't outputting if the Batt (charging ) light on the dash stays lit when the engine is running. That will confirm no alternator output.

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Re: Weird electrical problem ruined my car!

Post by GiveMeABreak » 25 Nov 2018, 11:33

I think you'll find it extremely difficult to drive without power assistance, but if you want a circuit diagram, I'll need your VIN.

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Re: Weird electrical problem ruined my car!

Post by Peter.N. » 25 Nov 2018, 11:54

Assuming your alternator has a separate 'field' connection, normally the small one, with that connected it shouldn't hurt to run it with the alternator disconnected unless the system is radically different to any I have come across, mine are mainly older cars though. with that lead disconnected you shouldn't have any output from the alternator unless the regulator has an internal short.

For the cars I am familiar with you can usually get a replacement brush/regulator assembly quite cheaply.

Peter

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