Volvo RWD 900 Forum

INDEX FOR 10/2025(CURRENT) INDEX FOR 1/2010 900 INDEX

[<<]  [>>]


THREADED THREADED EXPANDED FLAT PRINT ALL
MESSAGES IN THIS THREAD




  REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

MCC Control Unit doesn't work... No AC... 900 1993

posted by  KDMiller on  Thu Sep 23 05:42 CST 2004
Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS] [RELATED]

I have a 1993 940 Sedan - 136K miles. The AC compressor quit working the other day. I researched the FAQs and checked the following items: There is no voltage signal at the green/red wire connection to the white wire that goes to the compressor. I pulled the MCC and checked the power at the little black relay on the circuit board (which was good). I also resoldered the connections for good measure, and have voltage there as I should. When I switch on the AC button, I can feel the relay energizing, but the surround lights for the recirc button and AC button don't light up. The Chilton manual I have for this model doesn't show any schematics for this model. So... are there other items I should be looking at? The AC system has a good charge (verified with a 134a pressure gauge)and if I run a wire from the battery to the compressor white wire, it immediately runs fine and cools down like it should. Any and all opinions and suggestions welcome! Thanks!

Keith Miller







  •   REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

    MCC Control Unit doesn't work... No AC... 900 1993

    posted by  spook on  Thu Sep 23 07:06 CST 2004
    Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
    last visit: Fri Oct 24 08:06 CST 2014
    [RELATED]

    Dear Keith,

    Good p.m. and may this find you well. You've hit the key points. On the MCC printed circuit board, did you also re-solder the main connector contacts (12 or 14, can't recall), which are right behind the relay? Those, too, sometimes fail.

    It might be the case that the pressostat - the switch on the accumulator - has failed. If it does not work, no power gets from the MCC to the compressor.

    You can jumper the pressostat. With the ignition off, remove the connector, and jumper the contacs. If the compressor turns on, the pressostat needs to be replaced.

    Hope this helps.

    Yours faithfully,

    spook








  •   REPLY TO THIS MESSAGE    PRINT   SAVE 

    MCC Control Unit doesn't work... No AC... 900 1993

    posted by  rwreagan on  Thu Sep 23 06:46 CST 2004
    Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
    last visit: Sun Aug 14 15:41 CST 2011
    [RELATED]

    There have been numerous reports this forum about circuit boards in the climate control units failing with microscopic cracks in the circuit paths on the boards. They normally can be repaired by resoldering.

    There's lots of information in the faq. Look for the A/C section, especially in the MCC Not Working section.

    Good luck
    Robert







<< < > >>



©Jarrod Stenberg 1997-2022. All material except where indicated.


All participants agree to these terms.

Brickboard.com is not affiliated with nor sponsored by AB Volvo, Volvo Car Corporation, Volvo Cars of North America, Inc. or Ford Motor Company. Brickboard.com is a Volvo owner/enthusiast site, similar to a club, and does not intend to pose as an official Volvo site. The official Volvo site can be found here.