My son just got an '86 300e and the blower motor is not functioning. It does not appear to have the fuse upgrade (or at least we cannot find it if it does) and the blower motor is not getting the 12 volt signal. After removing and checking the motor we did some more diagnostics and I find that the plug behind the brake booster does not have 12v on the red lead. The yellow lead ranges from 1 - 6 volts when the fan switch is adjusted. Black lead appears to be ground and is ok. If I put 12 to the red lead the fan works correctly. Now my question.

Where does the red lead on this plug get the 12v from? Could this be due to a blown fuse (if not obviously)? After checking both sides of fuse 12 in the fuse box there is no power there whatsover and it looks a little melted on the bottom side. How would I go about getting the 12 volts from the fuse box to the red lead? Can I just get an inline fuse (30 amp) and do the upgrade myself without a MB kit? How do you get into the fuse box to get the power? I have tried loosening the 6 screws I see for the fuse box and cover and it will not open. We have the repairs CD's but they are not helping with my limited electrical knowledge.

Thanks to any and all who can help. This is his first car and he cannot drive it unless he gets some heat. I am sure you all have felt the same as him about wanting to drive the car you just bought. Thanks again in advance.

welcome

use the 'search' feature, a very discussed topic.

http://www.peachparts.com/shopforum/search.php?searchid=175983

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*92 400e 124.034, SOLD

*92 300e 124.030, SOLD

I understand how often the topic has been discussed. I have used the search option and that is how I found out what I already know (having read every single one of them for the past 40 days). These are very specific questions that have not been answered on this board (at least that I can find). I am well aware of how these boards work and do not mean to take up bandwidth. If anyone can help it would be appreciated. Thanks

There was a mid year change to an exterior 30A , as you already know.
The fuse mod was simply put in parellel with fuse 12 [ 25A]
You have to get to the bottom side of the fuse panel #12, where you will most likely see the wires burnt. If you can clean the feed wire back , hook a new exterior fuse to this feed and splice the other end into the red wire . That will give you fuse protection and feed only when key is ON.
Use heavy stranded copper.
That's it.

Thanks for the info Arthur. I still cannot figure how to get to the bottom of the fuse box. I see on other posts that you have to go through the dash panel on a w126, I hope it isn't that difficult on a w124. I have taken the 6 screws off the top of the fuse panel (2 at the front, 2 at rear of fuse panel and 2 at rear of relay panel) but cannot get to the bottom of the fuse panel. Is there some kind of secret to getting in there? The red wire comes out of the firewall at the rear of the brake booster and the socket that plugs into it appears to go to the resistor pack. Any idea where to find this wire behind the firewall? That would probably be the best place to splice into it. Would it hurt to splice into it on the harness for the resistor pack? The last few questions would probably be mute if I can find out how to get into the bottom of the fuse panel.

Once again, thanks for all the info you have provided.

On my 1990 300E you remove the screws and lift the fuse panel out.

With the battery disconnected, of course!

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2012 E350
2006 Callaway SC560

I have a similar problem on my 126 SD, no heat and it is -20 C here today!! not fun but I park facing the sun and it keeps the windscreen clear. How do you get at the bloody heater fan? My problem is not fuses, I checked. Anyone with suggestions?

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The meek shall inherit the earth, the brave shall get the oceans