W140 Heater Fan Only Operates On Slow

[Baracuddda]

hello all

I have a 1994 W140 S500 coupe
Alas although the heater fan apparently works it will not work on demister setting or faster setting.
CAn anyone help.

Bara

 

[television]

Yes sir, you need to change the regulator pack 252 in the link

http://www.detali.ru/cat/oem_mb2.as...722.370620&CT=F&cat=44K&SID=83&SGR=045&SGN=01


Ebay is a cheaper way to go or ask euromerc in my signature

 

[jberks]

hello all

I have a 1994 W140 S500 coupe
Alas although the heater fan apparently works it will not work on demister setting or faster setting.
CAn anyone help.

Bara

Does it not speed up to the faster settings and stay slow, or does it die when you select the faster setting? Malcolm is undoubtably right on the reg pack but I'd check the signal voltage from the control unit to the reg pack first to ensure the controller is behaving as it should. Assuming it rises normally (0-7v ish depending on how fast you want the fan to run) then the regulator is the issue.

 

[Baracuddda]

w140 heater fan

no it stays at a canstant speed all the time , it does not die on maximum
bara many thanks

 

[jberks]

Does sound strongly like the regulator pack but do have a quick check on the signal voltage before replacing.

 

[television]

The control box puts out 0 to5 volt. max fan speed is when the control box puts out 0 volt

 

[jberks]

The control box puts out 0 to5 volt. max fan speed is when the control box puts out 0 volt

Are you sure Malcolm? I thought the one I tested (on my 210 admittedly) went the other way around - 5v = max fan speed - actually given that the fan has a constant live, surely it must be that way around or it would switch to full when the ignition was off - or is a 140 different?

 

[television]

The regulator is a pair of darlington power transistors on the 4 wire device, when the reg packs up or shall we say goes faulty. On all of the ones that I have had they go open circuit, and therefor no drive, and the fan stays at the default level, and this is 5 volt

This info is on a very good 129/140 CD

 

[shayes]

hello all

I have a 1994 W140 S500 coupe
Alas although the heater fan apparently works it will not work on demister setting or faster setting.
CAn anyone help.

Bara

Interested in your symptoms and note the expert advice subsequent to your thread. hope you have solved your problem?

My own car doesn't seem to have any turbo blast when set to demist, and in fact the blower working on max auto setting "sounds" faster. Should it?
Demist took ages after I found snow on the screen the other day. Had to use rag or I'd be there now! Also, passenger side window vent doesn't seem to blow at all when opened on Demist setting or Auto.

On Auto, max blow with the setting "arrow up" alone, there's a lot of noise but little air on to the screen. I'm wondering where the air is going? How many sensors are there in the W140 I wonder, or could it be flaps not working properly?

Waiting on Repair Manual to understand whats behind bulkhead. My old 500SEL could knock the spots off his car when it came to heating and vent. Simple works everytime - bit like me!

 

[television]

Interested in your symptoms and note the expert advice subsequent to your thread. hope you have solved your problem?

My own car doesn't seem to have any turbo blast when set to demist, and in fact the blower working on max auto setting "sounds" faster. Should it?
Demist took ages after I found snow on the screen the other day. Had to use rag or I'd be there now! Also, passenger side window vent doesn't seem to blow at all when opened on Demist setting or Auto.

On Auto, max blow with the setting "arrow up" alone, there's a lot of noise but little air on to the screen. I'm wondering where the air is going? How many sensors are there in the W140 I wonder, or could it be flaps not working properly?

Waiting on Repair Manual to understand whats behind bulkhead. My old 500SEL could knock the spots off his car when it came to heating and vent. Simple works everytime - bit like me!

Your system is all vacuum controlled and a pipe could be off or flap stuck

http://www.detali.ru/cat/oem_mb2.as...GM=717.454&CT=F&cat=19B&SID=80&SGR=100&SGN=07

 

[Baracuddda]

Hello All
I bought a new (used) blower regulator and fitted it i can say that it actually works but not at the speed or power i was expecting it too. On demister mode it always on, on auto mode stays on fast for a few seconds and then slows down. I really thought it would be a much stronger blast ? Anyway its a lot better unless you have any other ideas.
Sorry i wont be able to make the pub at Honinton
regards Bara (Richard)

 

[television]

The way you say it works is normal, could there be faults on some of the flaps