Need help with HVAC W140 300 SE Bj. 1992

[300se1992]

Hello 🙂

Sorry for the English, I don't speak German (yet)

I have 1992 300se (m104.990) without aircon
vin: wdb1400321a013546

I struggle to find hvac blower resistor, because, well, the blower doesn't look like anything I found on the internet.
All pictures that I've seen show the resistor placed directly on top of the blower, but it's not what I see.

Is anyone familiar with this type of blower?

I've attached a couple of pictures, and the sticker that was on the blower housing

P.s> google doesn't know anything about the number that is covered by the black wire on my photos

[Fitzcarraldo1]

Zitat:

@Born2Rust schrieb am 29. April 2024 um 09:09:18 Uhr:

@Fitzcarraldo1

ich glaube Poppel1 hat den von dir angehängten Schaltplan nicht verstanden ?
Es wird der Lüfterschalter S3 gezeigt und der Motor mit den Vorwiderständen.
Da will Poppel1 irgendwie einen elektronischen Regler einbauen der werksmäßig nicht verbaut war.
Der Kabelsatz ist auch ganz anders, ich glaube du solltest dem TE empfehlen das zu machen was
offensichtlich ist.
Fußnote wurde auch nicht verstanden, blindes Vertrauen in den Mercedes Mitarbeiter ?

nicht jeder kommt mit Schaltplänen zurecht, bestes Beispiel hier.

[poppel1]

Kann sein das ich das nicht verstehe. Klar. Wenn aber der Widerstand kaputt ist, um das Teil mal so zu nennen, sollan den tauschen können gegen ein anderes Teil. Also wäre mein Plan ausbau und Messen und ggf. Eine Teilenummer finden und vergleichen. Bei Mercedes redet man von fällt weg und ersetzt sich in.

[300se1992]

Wow, I didn't expect to get so much help here and so fast
Thank you, everyone, and especially Fitzcarraldo1

This info helped to clear things up

[300se1992]

Hi everyone,

A quick note here about my progress on this matter:
I disassembled the central console and got my hands on the blower speed control knob (photo attached). As far as I can tell, this regulator is in working condition (I've checked the circuit on each of the 4 contacts). I wasn't able to find the resistor yet. As Fitzcarraldo1 suggested, it should be near the brake booster - it's not there. I've also found a picture on the internet that shows this type of resistor could have been mounted near the exhaust pipes (on my car it's not there either).

I've tried to trace the wires coming both from the blower motor and from the control knob. The wires from the blower go to the interior as I drew on the images, and the wire from the control knob goes somewhere behind the dashboard.

[Fitzcarraldo1]

Hello 300se1992,

your image #4 clearly shows the 4postion switch for the 4 fan speeds supplying the 3 pre-resistors and the top speed contact in the resistor group.

However, you have not dug deep enough - yet. You need to dig deeper.
I am attaching the removal instructions of the resistor group below. Apologies for not attaching it before.

As you can see in the image, you need to remove the articulated wiper module and the water collector.
Then you'll see the pre-resistor group.
Mercedes-Benz have a habit to place such items, that dissipate heat, in the air stream in order to cool the device.

(unfortunately, most of the images on WIS for such old cars have been copied from Microfiche - hence the lack of clarity)

Good luck with your search.

Fitzcarraldo1

[300se1992]

Thank you for your input!

Yes, that’s what I thought, but I was a bit afraid to disassemble the wiper mechanism. I’ll write here back when I do it.

I got this car only a couple of weeks ago and it requires a lot of attention. It has been sitting in the garage for the past 10 years or so

Again, thank you for your help

[Fitzcarraldo1]

Zitat:

@300se1992 schrieb am 13. Mai 2024 um 13:38:36 Uhr:

Thank you for your input!

Yes, that’s what I thought, but I was a bit afraid to disassemble the wiper mechanism. I’ll write here back when I do it.

I got this car only a couple of weeks ago and it requires a lot of attention. It has been sitting in the garage for the past 10 years or so

Again, thank you for your help

The wiper system does not really have to be dismantled to the point where you lose alignment, you are not detaching the motor from the mechanism.
To start, you can move the arm into the vertical position by hand with the ign/key removed and later back to horizontal to extract it.

[300se1992]

Noted, thank you