DIY Blowser Regulator Replacement and Diagnosis...

[MikeJT]

Originally Posted by samosali

I went into AC self diagnostic mode and put fan speed to MAX, but I can hear that this is not what it was few months ago when I replaced blower regulator, thus I do not need to measure voltage at the blower at all. I would say it works with 75% of power.

But I also noticed that refrigerant pressure temperature was not under 6 °C during the test. Maybe this influences the fan MAX speed also?

I paid 215 EUR for HELLA regulator, it seems that I will have to buy BEHR at the dealer. is it necessary to use the dielectric paste only at the contact REGULATOR-HOUSING, or at the entire regulator's back side because the new regulator is larger than the original one?

A few questions/comments:

1. Did you check that #8 in the a/c diagnostic mode was reading 60 when the fan speed was set at max? If not then the a/c controller may have a problem.

2. I am reasonably certain that the fan speed is not affected by refrigerant temperature if you manually select max. fan speed.

3. Is your external air filter in good condition? - a blocked filter can reduce the fan speed. I would certainly check this before condemning the regulator.

4. The paste is there for its thermal conductivity properties not its dielectric strength. You need a thin film of it to exclude any air (bad conductor of heat) between the area of the regulator's heat sink that is in contact with the blower case. This just makes the blower case act as an even larger heat sink for the regulator's power transistor(s).

Mike

[samosali]

A few questions/comments:

1. Did you check that #8 in the a/c diagnostic mode was reading 60 when the fan speed was set at max? If not then the a/c controller may have a problem.

it was reading 60 with fan speed on MAX.

2. I am reasonably certain that the fan speed is not affected by refrigerant temperature if you manually select max. fan speed.

makes sence.

3. Is your external air filter in good condition? - a blocked filter can reduce the fan speed. I would certainly check this before condemning the regulator.

The filter is about 6 months old, 7000 km on road and it was cleaned few weeks ago. It is 99,99% not a filter.

4. The paste is there for its thermal conductivity properties not its dielectric strength. You need a thin film of it to exclude any air (bad conductor of heat) between the area of the regulator's heat sink that is in contact with the blower case. This just makes the blower case act as an even larger heat sink for the regulator's power transistor(s).

The point is that the regulator which I replaced 6 months ago has much larger contact surface then the old one. In another words, the surface on the blower housing which is slightly higher than the surrounding surface is smaller than the surface of the regulator. i assume the new regulator was not mounted properly by me ... but they sold me a regulator as a part which should work with old housing.

Should I modify the housing of the blower to match the surface of the regulator?


This is an update made some time after the above text:
1) if i select internal circulation of the air I can hear full power of blower, thus evidently the air filter prevents full air flow from outside. how is this possible with filter 6 months old?
2) i tried to measure the voltage between the red and blue connector of the blower motor (both plugs disconnected). I expected that according to fan speed selector wheel in the cabin the voltage will be different ... from ca. 1 V to 12 V, but it is constantly ca. 12 V. So I am not able to verify the regulator at all.
Any tip?

[BENZBOSS]

Originally Posted by samosali

Should I modify the housing of the blower to match the surface of the regulator?

NO,I just put my new/big one and its OK,NP for the last year.

Old Bosch



New/big H.T.

[samosali]

thanks for the two pictures and explanation. I am really bad in electricity ... how can I measure the voltage at the blower motor which should be proportional (inversely proportional) to the blower RPM? Only an exact instructions can help me (please see my edited text above).

[MikeJT]

Originally Posted by samosali

thanks for the two pictures and explanation. I am really bad in electricity ... how can I measure the voltage at the blower motor which should be proportional (inversely proportional) to the blower RPM? Only an exact instructions can help me (please see my edited text above).

I don't know the details of the regulator circuit but it maybe that the output transistor doesn't draw any current if the motor is not connected. In this case, the blue line would probably be within about 1 volt of ground potential, giving you about 12 volts between the red and blue lines, whatever you do with the speed control knob.

The red line is connected solidly to the battery +12 volts so that you can check that one when it is disconnected by measuring between it and the car metalwork. For the blue line I suggest that you carefully ease back the translucent insulating cover on the motor connector of the blue line while both red and blue lines are connected to the motor, exposing enough of the blue terminal to get a voltmeter prod on to it. You can then measure between this terminal and ground (car metalwork) at various speed settings. The higher the speed, the lower this voltage should be.

As for your external filter which you now suspect, if it looks OK maybe the air intake itself is blocked with crud.

Mike

[MOS500]

Originally Posted by samosali

thanks for the two pictures and explanation. I am really bad in electricity ... how can I measure the voltage at the blower motor which should be proportional (inversely proportional) to the blower RPM? Only an exact instructions can help me (please see my edited text above).

My original post clearly shows were to measure voltage.

[samosali]

Thanks for an idea. It is dark now here. I will try it tomorrow. I will also check the air ducts to the blower. Maybe the best solution is to buy a filter without charchoal? I will also check if rotation of the blower is not hindered by worn bearings.

My original post clearly shows were to measure voltage.

Oh yes. sorry, I even did not look at the start of this topic because there is another older thread about this problem ... and there the procedure of measuring is not clear.
I will do it tomorrow, thanks to you, too.

[samosali]

So here is the report:

1) I oiled both bearings
2) checked air ducts to the blower ... NP
3) checked brushes on the blower .. still OK
4) measured voltage on the terminals like suggested in this topic: 10,6 V at MAX fan speed, 2,6 V at MIN speed.

It seems that the regulator lost at least 1,0 V. Evidently it started to die.

I paid 215 EUR for it and its HELLA, it is stated BEHR on it. I think the next one will die too. Any tip?

[MikeJT]

Do you have an activated carbon filter? I have an Introduction manual which states that:

'Upon switching on the activated charcoal filter, the blower motor control voltage is increased within 1 minute. This assures a constant air volume from the blower motor.'

I don't have the carbon filter so can't find out the implications of this but it seems to indicate that the voltage across the blower motor would be less if the filter is switched off.

Maybe it's irrelevant to your investigation - I can't tell.

Mike

[MOS500]

Originally Posted by samosali

So here is the report:

1) I oiled both bearings
2) checked air ducts to the blower ... NP
3) checked brushes on the blower .. still OK
4) measured voltage on the terminals like suggested in this topic: 10,6 V at MAX fan speed, 2,6 V at MIN speed.

It seems that the regulator lost at least 1,0 V. Evidently it started to die.

I paid 215 EUR for it and its HELLA, it is stated BEHR on it. I think the next one will die too. Any tip?

I think you are OK with voltage, 1V difference is not bad especially if your car was not on. Mine was so degraded that I only got 3-4V at full speed which was the same as very low speed.