My 1987 560sl air conditioner will randomly blow HOT air. The air conditioner will start out working properly...When I shut the car off & then return to restart it, the air conditioner will blow HOT air instead of Cold air.. The compressor has recently been replaced & refilled with the proper coolant. Somethimes it will blow the cold air & then it will suddenly start blowing hot air. Does anyone have any ideas what could be causing this problem? THANKS

Start by checking Klima relay and the monovalve.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

I think various Mercs (I have a 560 SEC) have a sort-of default setting where if the monovalve/duovalve fails to work properly, the system blows hot air whatever you do to the control settings (and on my car the recirc switch telltale light flashes). Apparently it's so that you can at least limp home with windscreen demisted!

I could find nothing about this in the handbook or workshop manual, but I eventually tracked down a tech article on the internet. Unfortunately I can't now trace it. But check the monovalve/duovalve anyway: there are forum posts about this problem - apparently they sometimes stick.

Good luck!

I too hate that when it happens.....I usually get out and wiggle the fuse and all is ok (No.7)

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Timothy Evans
TimEvans35@gmail.com
CELL 310 990 6780


1985 380 SL
2010 CL 6.3 AMG
*2009 CL 550 Sport 4matic
New addition-1984 380 SE
Newest Edition 1986 300E AMG