Hearter Fan is there a relay or something to cause intermitent operation?
 

Heater motor only working sporadically when starting car then turns off, then when accelerating (with added rpm the motor goes on again):confused:
Have checked the motor does work connected to 12 volt power motor spins freely. Not sure how to check switch if faulty?
Car is w123 wagon 1982 280te. Fan did not work for some time then pulled motor to check, this was subsequently fine.(as stated above) Also checked fuse was told they heat up and cause intermittent power but fuse ok.:confused: What could be cause, any help appreciated????
Summer coming on and air would be great.
Switch seems to control a lever above fan motor behind dash, it moves freely. Is this switch also connected electrically (3 Speed Dial type)?
Please help can't even put on defrost when I need to.:mad:
kind regards
BB from down under
P.S.
Did look thru past posts but not able to find similar post.

Often times it is the brushes on the motor that have worn down to the limits of making contact. The motor becomes very intermittant at that point.

My motor went dead after a while, so I posted a topic to this forum. MBDOC told me to check the ignition switch, and when I took it off, sure enough, it was the culprit. It makes sense that after a million turns, the contacts on those switches wear out. Well, I've replaced it and my motor is blowing fine again. Maybe you should look at that.

re Squid
 

Hey there squid how does the ignition switch have control over the heater motor?
Sorry if I sound silly but am serious dont know the connection?
Please if you have time respond or include the link to that forum that would be great.
Kind regards
BB:)

p.s. re squid
 

Sorry squid also the motor seems fine it runs great with 12 volt to it but looking for some connection to switch gear maybe power not getting thru properly.:)
Kind regards
BB

Your car contains electrical components that are wired directly (relatively speaking) to the battery (e.g., headlights, courtesy lights) that have power all of the time, and components that are wired through the ignition circuit (e.g., heater motor, radio, wipers, power windows) that don't receive power unless the ignition switch is in good order and the ignition key is turned to the proper position. If the electrical contacts inside the ignition switch are worn, electrical current will flow in an intermittent manner, or not at all, even if the key is in the proper position.

Try this: Next time the heater motor won't work, turn the heater motor switch to a running position, start the car and move the ignition key around (very slightly when turning it forward, to prevent accidential engagement of the starter), push it in, etc. Generally, manipulate the key in small increments in every possible direction. See if the heater motor comes on, even briefly. If it does, the ignition switch is the culprit and must be replaced.

These switches wear prematurely if the ignition key is attached to a heavy set of keys or keychain. The excess weight puts a mechanical strain on the switch.

re Paul C
 

Dear Paul C
Thanks for that explanation it makes very good sense and I will try it now , I will get back to you on how it went.
Thanks very much
regards
BB:)

Hey PaulC May have the problem solved
 

Hey there PaulC
Are you there?
Just did what you said Its not the ignition switch it is fine, did test with torch connected to power supply to fan motor works fine.

Then connected the power to fan it did not work accidently turned fan upside down bingo fan works.
Turn it round right way up no go, upside down it works again???:confused:
Then put it right way up put a bit of pressure under drive shaft on fan and bingo it works :D .

But remove pressure and same again no connection and no power?

Does this mean that the bearings may be gone do they have anything to do with power supply or is it a case of resistance and fan motor cannot spin??

What happens now can I replace bearing , or is it time to get new motor?

Today is Sunday here am going to dealer tomorrow to pick up wife's 190e after some work, will pick up relevant bits tomorrow.

thanks for your help.

kind regards
BB;)

The problem is clearly in the fan motor - Often times it is the brushes on the motor that have worn down to the limits of making contact. The motor becomes very intermittant at that point.

Can't you just replace those carbon brushes. There's an online article about this posted by a member of this forum:
http://www.mercedesdot.com/newsletter/issue8.htm

re Squid
 

Hey there Squid
Had a look at that site and yes the brushes were replaced that solved the problem.
Much appreciated to all at Mercedesshop once again.
Thanks from down under.
regards
BB;)