Battery warning light stays on as soon as I start the engine.

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LFY
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Re: Battery warning light stays on as soon as I start the engine.

Unread post by LFY »

ekjdm14 wrote:
06 Jun 2020, 00:50
Well, that's A way to check, I suppose. Have you got the multimeter working yet? Could it be the light is on but it's still charging after all? That's the main reason to use the actual test gear, stops you from getting led astray & it wouldn't be the first time a warning lamp has told lies (for example, 1.9TD oil level warnings/early Xantia water-in-fuel warnings to name just two common ones).
Really you need to check if it is charging first off, and assuming not, check for any output at the alternator itself as mentioned above as well as any signal voltages it needs. Then you can work from the results you get, it may just be a blown fuse preventing the alternator from "seeing" that the ignition is on but the multimeter should be your first priority to fix/replace ;)
Thanks for your help.
No, my multimeter is not working yet and I couldn't find its problem but I borrowed another device to check voltage and the result was negative (no charging). My alternator didn't charge the battery and the voltage was 12V which means the car was running on the battery alone without being charged. So, my warning light is real and alternator is not doing its job. Now, I want to know which part inside the alternator is causing the problem. Voltage regulator or other parts?

By the way, this is my multimeter. As you can see in the following video, it just blinks without showing any voltage!


I'm really unlucky because my alternator and multimeter both went wrong at the same time! :(

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white exec
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Re: Battery warning light stays on as soon as I start the engine.

Unread post by white exec »

That flashing of all segments on a display is normally what happens when you connect a fresh battery.
Try the User Instructions for the meter, and see what you need to do next.
User instructions can usually be downloaded from the web (the manufacturer's website) in your preferred language.

Unless you feel confident to open up the alternator and change its regulator circuit (and maybe brushes, if needed),
it might be a good idea just to exchange it for a serviced replacement.

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LFY
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Re: Battery warning light stays on as soon as I start the engine.

Unread post by LFY »

white exec wrote:
06 Jun 2020, 12:42
That flashing of all segments on a display is normally what happens when you connect a fresh battery.
Try the User Instructions for the meter, and see what you need to do next.
User instructions can usually be downloaded from the web (the manufacturer's website) in your preferred language.

Unless you feel confident to open up the alternator and change its regulator circuit (and maybe brushes, if needed),
it might be a good idea just to exchange it for a serviced replacement.
Thanks again for your support.

Do you think the part that is most likely to cause the problem is the VOLTAGE REGULATOR (and brushes inside it)? Do these parts are the most common cause of alternator failure?

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white exec
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Re: Battery warning light stays on as soon as I start the engine.

Unread post by white exec »

Those are pretty much the only parts that fail.

If you've checked that the alternator is getting its external supplies
— +12 from IGN sw
— a good Gnd connection (usually via alternator mounting frame, but also check no resistance between alternator frame and Batt–
— a good connection from main output terminal to Batt+
— good connection of the warning light (you seem to have this)
— maybe one other terminal, which is also connected to Batt+, and senses the battery voltage (not present on all cars or alternators)

On the fusebox, there may also be a fuse marked 'Alt', often around 5A.

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LFY
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Re: Battery warning light stays on as soon as I start the engine.

Unread post by LFY »

I disassembled inlet manifold, throttle body, oil vapor hoses, the whole intake system, fuel line and oil filter to gain access to the alternator!
I opened alternator cover and removed voltage regulator. I found the problem. One of the brushes had worn out but the other one was quite healthy.
I suspected the springs behind brushes. I pushed them with my hand and I felt that one of them was weaker than the other and this can be the reason for contact failure between slip rings and brushes. What do you think?

I couldn't find my original Bosch voltage regulator but after searching for a while, I found a Taiwan based company named Mobiletron (Automotive Electronics Manufacturer) which had a website in which they had stated a list of regulators. I found a model that was the alternative of my Bosch regulator with exactly the same serial number.

I checked the spring pressure of the new regulator and both springs had equal force. I installed it on the car and assembled all the parts back. I charged my battery and then started the engine. The battery warning light disappeared and now the voltage is around 14.2V with the engine idling (no load).

The attachments are the pictures of my Bosch and the new regulator I bought.
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