W124 heater fan cooking fuses

[Celicasaur]

SO....a few weeks back, my W124 decided to melt the fuse for the heater fan and bring paint to my life. I replaced the fuse and idled the car for a few minutes...seemed fine, so I forgot about it. I went back to the car later that same evening, fired up the motor but the fan wasn't working. A quick check under the hood showed that the fuse was cooked again.

Today I removed the front wiper mechanism to see if there were any issues with the fan squirrel cages (bearings), but they seems firm and silent when I was spinning them around. I have some numbers taken with my multimeter for you guys to assess

Engine off but key position #2:
Battery voltage 12.2v
Voltage at the fan fuse (#12 I think) 10.5v
Voltage at the squirrel cage pos/neg terminals 8.8v
Resistance at the fuse of 1.0 in the 200 ohm setting on the multimeter

Engine on:
Battery voltage 14.4v
Voltage at the fan fuse (but the fan operation is 'off' at the dash knob) 14.4v

Any ideas?

 

[219]

Worth putting some spray lubricant into the bearings when you have it running , they do tend to seize .
Otherwise replace motor

 

[Celicasaur]

Revisiting this one and pulling my finger out because oh no, the Winter is almost upon us.

A new motor sadly hasn't been able to cure the issue. Therefore, I need a new resistor. The problem is, I'm not sure where to find it and of course I'm not sure which one to order. I called my local MB dealer and they said that they've been discontinued. I look on eBay and see a few difference types. There's a type with fins like a shark and another with spikes like a hedgehog. I've taken a punt on the shark one and will likely hard-wire it in if the connectors don't match up. I'll update this thread if/once I've managed to resolve the issue so that somebody will have an idea of what it took to solve this issue on my car.

 

[Celicasaur]

Ok so that ^ was an epic fail and £30 or £40 that I'll never get back. Connectors dont work and the number of wires don't match up to the oem resistor thing which means the only way to make it work is to hard wire it to the circuit and even then it will only work on the highest fan setting...a solution of sorts, but not the one that I'm looking for.

SO anyway I managed to source a healthy/verified used resistor from a champ in Latvia via eBay, thinking that would cure the issue.....nope, still popped a fuse right away. Here's what it looks like for those of you who don't know...it's very unusual compared to modern cars and so even if it's right in front of you in the engine bay, you'll struggle to identify it as a heater resistor.

This is where it lives in the engine bay, should you ever need to bash it with a hammer:

At this point I thought screw it, time to just cut my losses and buy a brand new one that wont have any potential old gremlins which i don't know about.

So, back onto good ol' eBay again and I bought this for a reasonable £70 or so incl postage

Blower Motor Heater Blower Fan for Mercedes W124 W210 New | eBay

Find many great new & used options and get the best deals for Blower Motor Heater Blower Fan for Mercedes W124 W210 New at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

Fits fine and whoop! I have my heater working again finally! Only took me over 6 months to get this sorted

SO, moral of the story? When it comes to electrical, buy new, even if it's 'cheap' new. Even if it lasts 5 minutes, at least you'll know that the circuit would have at least been fit for purpose for the sale. Buying a used blower motor which had an existing issue just like my original one which failed, meant that I went down a whole path of pain and mis-diagnosis in order to end up back at buying a motor again.

Anyway. My heater works now and so now I can fit my bloody wiper arm back on...it's been off the car for over 6 months, so that I'd have easy access to the motor whenever I could be bothered to look at it.

One more thing off the list. Next stop > the windscreen wiper motor and assembly. I tell ya....whoever buys my car next year will be the luckiest W124 cab owner in the frickin world