Funny Business with the Fuse Box...

[astroe]

Hi all,

This is related to my whole "fan blower won't work" saga - it's practically all I post ever about!

So I had a look at my fuse box today and was pretty perplexed.

IMG_9839.JPG

There's no #12 fuse for the fan blower, and it says "outside", handwritten on the fuse key.

IMG_9840.JPG

Lo and behold there's a small little offshoot to the side, with a part number starting 123...

IMG_9841.JPG

And inside it?

IMG_9842.JPG

I'm really confused - is this normal?
What is going on?!

[T-Modell]

Hi,
on No 12 there's two stars, which says on the bottom that with automatic aircon the fuse's outside ...
Thomas

[astroe]

Hi,
on No 12 there's two stars, which says on the bottom that with automatic aircon the fuse's outside ...
Thomas

I thought I had Tempmatik and not the automatic air conditioning anyway? (The dual zone one rather than the single temperature control one).

Even if that’s the case, the wiring job on the outside looks pretty... haphazard.

[Henry Schuman]

Back in the day a lot of those period autos had overload with the Blower Motors and a Service Bulletin was issued to Relocate the Blower Motor Fuse to the outside and a Higher Amp Fuse however I never saw ( Noticed) the indications listed in this post on the Fuse Box Description.
Good Eye T-Model .
If you look closely at that fuse area #12 you can see it looks like melted plastic thus indicating an over heating problem >

[astroe]

Back in the day a lot of those period autos had overload with the Blower Motors and a Service Bulletin was issued to Relocate the Blower Motor Fuse to the outside and a Higher Amp Fuse however I never saw ( Noticed) the indications listed in this post on the Fuse Box Description.
Good Eye T-Model .
If you look closely at that fuse area #12 you can see it looks like melted plastic thus indicating an over heating problem >

Noted - but does the outside fuse box look weird at all? It’s held together with electrical tape and inside the fuse box there’s just a screwed in metal plate?

[T-Modell]

Hi this seems to be ok, might be a 50A fuse ... have a look here: https://de.ifixit.com/Anleitung/Mercede ... ment/20410

The number is mainly referred to as a glow plug fuse ...
Thomas

[John Green]

Hi this seems to be ok, might be a 50A fuse ... have a look here: https://de.ifixit.com/Anleitung/Mercede ... ment/20410

The number is mainly referred to as a glow plug fuse ...
Thomas

Melted fuse holders in the W124 fuse box are common, Henry is right there was even a MB tech bulletin about it. However I would be concerned with the size of that fuse they have put in. As you can see the original fuse is 24 amps. It does look like you now have a 50 amp fuse....

[astroe]

Hi this seems to be ok, might be a 50A fuse ... have a look here: https://de.ifixit.com/Anleitung/Mercede ... ment/20410

The number is mainly referred to as a glow plug fuse ...
Thomas

Melted fuse holders in the W124 fuse box are common, Henry is right there was even a MB tech bulletin about it. However I would be concerned with the size of that fuse they have put in. As you can see the original fuse is 24 amps. It does look like you now have a 50 amp fuse....

Sorry for the dumb question but what would the implication of having a 50 amp fuse instead of a 24 amp fuse be?

[T-Modell]

...Sorry for the dumb question but what would the implication of having a 50 amp fuse instead of a 24 amp fuse be?

The current is what kills, not the voltage. If you have some electrical equipment that can handle e. g. 30 Ampere and you have a fuse of 25A, it is safe, as the fuse blows up, before the current gets too high (e. g. short cut). If you put a 50A fuse in it, it will allow currents up to 50A, so it could kill whatever's connected.

Similar to the old "Elektrotechnik" say: the transistor protects the fuse by blowing up first ... happened to me once at university ... luckily, this transistor really protected the whole rest of the circuit board :whistle:

Regards
Thomas

[astroe]

...Sorry for the dumb question but what would the implication of having a 50 amp fuse instead of a 24 amp fuse be?

The current is what kills, not the voltage. If you have some electrical equipment that can handle e. g. 30 Ampere and you have a fuse of 25A, it is safe, as the fuse blows up, before the current gets too high (e. g. short cut). If you put a 50A fuse in it, it will allow currents up to 50A, so it could kill whatever's connected.

Similar to the old "Elektrotechnik" say: the transistor protects the fuse by blowing up first ... happened to me once at university ... luckily, this transistor really protected the whole rest of the circuit board :whistle:

Regards
Thomas

Thanks Thomas!

So essentially I need to find an auto electrician to swap out the fuse for a lower one!
Unless anyone here knows what the amp limit for the fan blower motor is? :)

[T-Modell]

Well the fuse box says 25A ... sounds right to me ...
Thomas

[Henry Schuman]

...Sorry for the dumb question but what would the implication of having a 50 amp fuse instead of a 24 amp fuse be?

The current is what kills, not the voltage. If you have some electrical equipment that can handle e. g. 30 Ampere and you have a fuse of 25A, it is safe, as the fuse blows up, before the current gets too high (e. g. short cut). If you put a 50A fuse in it, it will allow currents up to 50A, so it could kill whatever's connected.

Similar to the old "Elektrotechnik" say: the transistor protects the fuse by blowing up first ... happened to me once at university ... luckily, this transistor really protected the whole rest of the circuit board :whistle:

Regards
Thomas

Thanks Thomas!

So essentially I need to find an auto electrician to swap out the fuse for a lower one!
Unless anyone here knows what the amp limit for the fan blower motor is? :)

What was happening is that the Original fitment in the Big Plastic Fuse box the wire ends got hot enough to Melt the plastic that held the brass retainers so they would move away from the Fuse causing arcing thus killing the otherwise Good circuit but rarely blowed the fuse but rather not allow a good connection so the motor would quit until you wiggled the fuse or bent the prong in on the fuse holder to make a better connection and eventually it just would not hold enough Tension so the Wise Old Cobblers decided to post a Bulletin to remotely mount a sturdier holder which was already being done by Ingenious MECHANICS :occasion5: ahead of the Engineers to remedy this oversight of plastic thickness/ heat non tolerant crap they originally put in.

I agree that a 50 Amp fuse is too much and the wire thickness was not Engineered for such a load and the mounting/ Electrical Taping Jury Rig is not of the Quality I would do . I would Recommend at least a Smaller fuse plate of 25 amps (and I think they are Available) and it is easy to replace by just loosening the two phillips screw had and removing the 50 AMP strip then slide in the 25 and retighten the screws and you are good to go.
Now SHOULD this 25 Amp Fuse Blow I would look into a NEW Blower Motor cause yours is on on the way out!

[astroe]

The current is what kills, not the voltage. If you have some electrical equipment that can handle e. g. 30 Ampere and you have a fuse of 25A, it is safe, as the fuse blows up, before the current gets too high (e. g. short cut). If you put a 50A fuse in it, it will allow currents up to 50A, so it could kill whatever's connected.

Similar to the old "Elektrotechnik" say: the transistor protects the fuse by blowing up first ... happened to me once at university ... luckily, this transistor really protected the whole rest of the circuit board :whistle:

Regards
Thomas

Thanks Thomas!

So essentially I need to find an auto electrician to swap out the fuse for a lower one!
Unless anyone here knows what the amp limit for the fan blower motor is? :)

What was happening is that the Original fitment in the Big Plastic Fuse box the wire ends got hot enough to Melt the plastic that held the brass retainers so they would move away from the Fuse causing arcing thus killing the otherwise Good circuit but rarely blowed the fuse but rather not allow a good connection so the motor would quit until you wiggled the fuse or bent the prong in on the fuse holder to make a better connection and eventually it just would not hold enough Tension so the Wise Old Cobblers decided to post a Bulletin to remotely mount a sturdier holder which was already being done by Ingenious MECHANICS :occasion5: ahead of the Engineers to remedy this oversight of plastic thickness/ heat non tolerant crap they originally put in.

I agree that a 50 Amp fuse is too much and the wire thickness was not Engineered for such a load and the mounting/ Electrical Taping Jury Rig is not of the Quality I would do . I would Recommend at least a Smaller fuse plate of 25 amps (and I think they are Available) and it is easy to replace by just loosening the two phillips screw had and removing the 50 AMP strip then slide in the 25 and retighten the screws and you are good to go.
Now SHOULD this 25 Amp Fuse Blow I would look into a NEW Blower Motor cause yours is on on the way out!

Thank you Henry - as it turns out, the car was purchased with a non-working fan blower motor and John the admin has been able to sell me one and it should be with me in the next few days.

Will definitely sort out the wiring issue so I don't have to get another motor...

[astroe]

Looks like the lowest I can find is 30 amps. Too high?

Screen Shot 2018-08-13 at 12.31.53 am.png

Alternatively I could replace the whole box thing that accepts a style of fuse that is available in 24 amps.

Screen Shot 2018-08-13 at 12.32.33 am.png

[Henry Schuman]

Looks like the lowest I can find is 30 amps. Too high?
Screen Shot 2018-08-13 at 12.31.53 am.png

Alternatively I could replace the whole box thing that accepts a style of fuse that is available in 24 amps.
Screen Shot 2018-08-13 at 12.32.33 am.png

I think you should be ok with a new motor and the \fuse .

[John Green]

The fuse in the outside holder, should have its amperage stamped into it, remove it and have a look.

[benzy53]

Hi astroe

If you look at the wiring diagram it shows that the blower motor is protected via a 25 amps fuse in the fuse box.
The two stars refer to the option for heated seats. ( I believe not available in OZ ). As the seat heating was connected
to fuse 12 as well it was placed outside. Over the years I had 14 W124 ( currently down to 3 ) and never seen an outside fuse and never any
issue with the blower motor. If you live in Melbourne you are more than welcome to PM me.

Regards benzy53

[astroe]

Hi astroe

If you look at the wiring diagram it shows that the blower motor is protected via a 25 amps fuse in the fuse box.
The two stars refer to the option for heated seats. ( I believe not available in OZ ). As the seat heating was connected
to fuse 12 as well it was placed outside. Over the years I had 14 W124 ( currently down to 3 ) and never seen an outside fuse and never any
issue with the blower motor. If you live in Melbourne you are more than welcome to PM me.

Regards benzy53

Hmm... that is concerning to say the least.
Will send you a PM.

[T-Modell]

...The two stars refer to the option for heated seats. ( I believe not available in OZ ). As the seat heating was connected
to fuse 12 as well it was placed outside. ...

Hi,
I disagree with that conclusion. Imho, there's two foot notes. One refers to an outside fusebox in case of seat heating and trailer coupling. This has no stars, separated by a line.

The two stars only refer to fuse 12 (blower motor) AND in case of automatic climate control this fuse is outside the box. Imho it could be another separate out-of-the-fuse-box fuse.

So what I would do: Follow the cable from the blower motor and see where it ends. Put a 25A fuse in and all is good. If you want to know it 110%, then you have to get a wiring diagram of your car with those specs ...

Regards
Thomas