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W124 fuse for Ac

robbieesprit

Member
Joined
Mar 28, 2019
Messages
43
Location
maidstone
Car
e320 estate
hi all
The ac On the w124 was not factory installed. So fuses are aftermarket and hidden away, any clues where the fuse is?
I can’t find mine...the controls inside have no power...I’ve had rest of system checked and it’s ok, just add power and it will work cheers rob
 
Can be any place it being some other make ac .You will need to trace back from the unit till you find them .Its like saying some one hid the key do you know where it was hidden
 
Many aftermarket W124 AIRCON setups were by a company called DIAVIA so it may help to do an internet search with terms like W124 AFTERMARKET, RETROFIT, AIRCON , DIAVIA One such search revealed a direct supply via heavy gauge wire directly from a live source to the aircon main supply switch fused but no relays involved- in that case there was a large aircon fuse in the base of the fuse box unit under the normal fuse/ relay panel. You don't say how your setup was tested as OK /gassed etc but I can't see how the entire system could be completely tested without power---visually inspected/gassed/leak tested yes but powered? I say this merely because in the absence of an obvious fault restoring power may simply blow the fuse again .
 
Thanks All
So here my thinking...
The tester just hooked up to a pressure gauge, and told me its not a "leaker", next job was to find the fuse, on doing this the fuse for the blower was found to be getting so hot it was melting the holder. So we pulled the fuse. The tester (50 years in the industry inc 17 years w124 ownership), said best to get a auto electrician to sort out an external fuse box for blower before you get a engine bay fire, I agreed. No charge for test.
On the way home, my thoughts turned to the cause of the over heating, my blower had been noisy for a while...so time to pull out the blower and have a look.
Im glad i did. The old unit would turn but with resistance, i.e you couldnt spin the hamster cages freely. Also, my pollen filters were full of sycamore seeds and muck, yet more resistance in the system...
I have also, serviced the wiper, and took all the plastic weather proofing out, serviced cleaned and painted.

So, if (BIG if) the ac and blower are on the same circuit, could it be that the extra amps drawn by the blower has fried something in the ac electrical side, i.e. a relay or control box...could be a likely cause?....I say this because the AC 3 weeks ago worked fine for demisting...so am thinking more electrical cause than mechanical for the moment.....
 
Mercedes had a habit of adding/secreting auxilliary fuses boxes and control units round the car as additional electrical services were added to the cars over the years- a good aftermarket system might have empoyed these but just as likely to cobble together some adhoc undocumented setup. IIRC circulating fan motor seizure was common cause of failure with the passing of years and replacements were becoming increasing difficult to source --- made from UNOBTAINIUM in some DIAVIA SETUPS.:(
check if see anything like these
https://w124-zone.com/downloads/MB CD/W124/w124CD2/Program/Chassis/54-1255.pdf
 
Thanks Graeme, very interesting, come to think of it my re circulating was playing up...another job on the list of things to do....i put it off as god knows how you get to it?? When it did work i got a loud thump...used to make me jumpl!! lol
Thanks for diagrams...will let you know how i get on....
 
Closing out issue....its fixed!
OK so i fixed my AC by returning to the first thing I checked....the fuses.
As part of the AC repair i decided to take the noisy blower fan out and service the wiper mech. That done i put it all back together and the wipers worked twice (very well) and stopped. This had me scratching my head, had the connector come off the back of the motor? no, the fuses looked fine, though curiosity touching the wiper fuse and it lept into action, a ha!!. On pulling the fuse I found that the ends had disintegrated, but leaving the visual fuse part intact. On replacing, my wiper work perfectly and nearly silently. I then thought, well if this fuse was like this, what is number 7 like (for climate, reverse light, aux fans etc...) bingo, the exact same issue, replacing fuse restored AC....well nearly....i still had to take out the duo valve and service this (it had a large lump of rubber in keeping drivers valve open.
Incidentally, the duo valve is easy to service, just need a little time on the kitchen table....I used a high temp water proof lube used for hot tubs seems to work well...
My only outstanding issue is the centre vents are not letting through air, which would be nice with the cold ac blowing....also i have to install a new fuse holder for blower...i dont fancy having a fuse box fire....
thanks all for assistance/ ideas with this cheers rob
 

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