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Old 21st January 2020, 16:14   #301
cosmin
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I found something...
1 ohm resistor broken. It could be seen only when i resolder it, came apart in 2 pieces.
Replaced it, he blow again. Replaced the 44N05 mosfet, problem still the same.
But this only happens when the glow plug is connected.

I have too high voltage on mosfet 44N05, according to picture.
Blue is on normal board, red is defective board. The values remain until the board enters in sleep mode.


Last edited by cosmin; 21st January 2020 at 19:22..
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Old 22nd January 2020, 06:18   #302
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High voltage values tell that voltage regulation / control is not working.


That circuit should be down to max 5v, the pin 19 is a PWM signal from 0-5v, so you have to find where the overvoltage comes from.



Basic electronics. Just replacing components without finding the root cause gets you nowhere. You have the schematics, so look for how that mosfet is controlled.

I suspect again a resistor. Something makes that mosfet to go fully open. There are only few resistors in that area..



And "44N05 mosfet", I can not find any datasheet with that, are there any other markings?


I hope you find it.
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Old 22nd January 2020, 06:22   #303
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No, there's just 44N05 marking on him. It's the mosFET near the 1ohm resistor.
I suspect it's the small 8pin opAMP. He's the one that controls it.

Last edited by cosmin; 22nd January 2020 at 06:24..
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Old 22nd January 2020, 06:28   #304
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Quote:
Originally Posted by cosmin View Post
No, there's just 44N05 marking on him. It's the mosFET near the 1ohm resistor.
I suspect it's the small 8pin opAMP. He's the one that controls it.
Something makes the gate go fully open, so you need to find whats there..
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Old 22nd January 2020, 06:35   #305
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I could find no other suspect components outside the opamp. I will replace it.
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Old 22nd January 2020, 15:57   #306
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Quote:
Originally Posted by cosmin View Post
I could find no other suspect components outside the opamp. I will replace it.
Check that there are no shorts with the IC MLCC caps.
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Old 22nd January 2020, 17:16   #307
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It was the OpAmp (LM2904), as expected. Replaced and the glow plug works just fine.
But the metering pump error came back. Same old "metering pump interruption".
The metering pump itself ticks 3 times, then throws the error, ventilating and after 1 minute, stops.
I already resoldered all resistors on front of the board.

Last edited by cosmin; 22nd January 2020 at 17:55..
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Old 23rd January 2020, 04:42   #308
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Quote:
Originally Posted by cosmin View Post
It was the OpAmp (LM2904), as expected. Replaced and the glow plug works just fine.
But the metering pump error came back. Same old "metering pump interruption".
The metering pump itself ticks 3 times, then throws the error, ventilating and after 1 minute, stops.
I already resoldered all resistors on front of the board.
Try the bulb trick, so instead of a real fuel pump, use a 12v 21W bulb, if the cycle works and the light flashes, the pump current might be too high.

But if I remember correctly, the other webasto board works with that pump, so then you have possibly another mosfet to replace?

If its working fine with low current draw, the mosfet pin might be partially loose from output pin, (it heats up and the pin detach from the circuit).

Do you have a way to test the current draw of the pump?
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Old 23rd January 2020, 05:40   #309
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Replacing the mosfet was the first move. But nothing changed. I used other metering pump too but same behaviour.
I have all the tools to measure the current through metering pump.
Will do all the tests you mentioned.
Thanks again!
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Old 23rd January 2020, 10:54   #310
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Quote:
Originally Posted by cosmin View Post
Replacing the mosfet was the first move. But nothing changed. I used other metering pump too but same behaviour.
I have all the tools to measure the current through metering pump.
Will do all the tests you mentioned.
Thanks again!
Also check the resistors next to the coil, between the coil and the CPU.
If I remember correctly, the other was 49.9k and other 4.75?

This could be a resistor now.. You had some many issues that I would double check everything.
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