W210 Fan Goes Bananas, Alarm, then Dead

rlx

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Hi,

I have a problem with my year 2000 E240 Estate (W210, I think). Yesterday on the way home from my son's birthday party the heater-fan control went haywire. Switching to the off position seemed to make the fan run faster, and switching to max speed seemed to slow it down somewhat.

That's fine, I can live with that. However at 4am this morning I was woken (and also I suspect most of the neighbours) with the alarm going off! I wasn't sure at first that it was my car since it wasn't as loud as it normally would be. I went outside to check and found that the door would not unlock. I had to use the manual key to unlock. There was no response when I put the key in the ignition. No noise (except the alarm) and no lights on the dash. The car was (and still is) dead.

I decided to disconnect the battery which was a feat in itself since a) I couldn't open the rear doors, b) the child-locks were on so I couldn't open then from inside, c) two large child seats were in theback which meant I couldn't wriggle into the back (hard enough without the child seats) and d) it was in the dark and freezing. EventuallyI managed, with some (actually a huge amount of) profanity, to disconnect the battery. Of course I wasn't surprised when that made no difference to the noise, since I suspect that the alarm/immobiliser has a backup battery.

Eventually (after about 90 mins the noise faded and stopped).

What is likely to be the problem?

Can I fix this without too much expense (I am still stinging from a £1600 bill to get the wheel bearing and brakes fixed a couple of months ago)?

If it's the immobilizer, can I just bypass it or remove it?

Any steps to troubleshoot would be appreciated.

P.S. Realized that the MB Handbook is crap. Fine when reading it smugly after having bought one but no ****ing Good(Tm) when reading at 4am.
 

television

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Hello and welcome with your not such good news

Its possible that the heater air intake box is blocked by leaves etc, and the grill in front of the screen must be removed to clear the drains.

The water on the electrics has probably killed the fan regulator.

The alarm could be waterlogged but not sure and I will post back later.

Any one else know more on this fault
 

Cole@MBS

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common fault with the 210, you need to replace the fan regulator, easy job, under the passenger side dash!
 

television

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The alarm unit is fully fault coded for a late 210, so putting it on STAR will give all of the right answers
 

Cole@MBS

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the 210s have a habit of making the fan run on when the reg fails for the heaters, what i suspect is that the fan has been running all night causing the battery to drain, hence alarm going of due to undervoltage !! connecting some jump leads and hearing if the fan if running is the simple way of finding out!
 
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rlx

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Thanks Guys, I'll check these out tomorrow.

BTW does anyone have a link to a picture of a fan-regulator so I know what to look for...?
 

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the 210s have a habit of making the fan run on when the reg fails for the heaters, what i suspect is that the fan has been running all night causing the battery to drain, hence alarm going of due to undervoltage !! connecting some jump leads and hearing if the fan if running is the simple way of finding out!

I'd agree with this. The fan reg has a constant live so if it does go haywire it could easily do as described. Don't be thrown by the fan behaving ok when it's powered up again - in my experience it can come and go. Mine wasn't as bad as you describe but it did behave perfectly 50% of the time, then suddenly go onto full for a few seconds before quieting down again. Mine whilstled too! They are around £130 from the dealer and 20 mins to fit for a vaguely skilled hamfisted amateur.
 
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rlx

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Haven't had a chance to check this yet due to other Christmas-related issues but before I start...

Has anyone ever tried fixing one of these, rather then forking out £130 (assuming access to electronic test equipment which I have)?
 

television

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sealed units - you can't get into them. The top is a cast heat sink and the bottom that shiny plastic stuff they pour in

Yes correct they are potted as we call it,, there is nothing that you can do with a semiconductor once it has in internal short,, as earlier its only a pair of output transistors wired in as darlington pair thats why it has 4 wires and not the normal 3
 
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rlx

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Well done you Guys... A million thanks. You have saved me from having the car towed to the dealer since I had assumed that the symptoms were indicative of something more serious.

I must admit my recent experience of MB workshops is that they smile at you and offer a cup of (****) coffee while coldly calculating how much they can stiff you for. I will never go back to an official MB shop again...

So, imagine with what glee I re-charged the battery and disconnected the blower power under the passenger dash. That was only a 5 minute job. I will not spend £130 or anything like it to get a heater fixed, so might rig up a switch to just flick it in and out (or more likely just do without it).
 

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Saving any amount of money these days is is always a bonus, good result!!
 

television

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I must admit my recent experience of MB workshops is that they smile at you and offer a cup of (****) coffee I will not spend £130 or anything like it to get a heater fixed, so might rig up a switch to just flick it in and out (or more likely just do without it).

If you do this, do disconnect any wires that feed back to the control unit, the control unit only gives out 5volt, and you will damage it beyond repair. so use a new feed
 


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