Results 1 to 7 of 7

Thread: How many volts at the A/C Compressor?

  1. #1
    Join Date
    Jul 2002
    Location
    Roanoke, Virginia
    Posts
    3,371

    How many volts at the A/C Compressor?

    Trying to button up a few of the last items on my 1995 SC, that weren't finished before the Hot Rod Power Tour. AC components were added back to this car after running with the systems fully removed for 3 years. Wife won't ride with me till they work, so trying to get systems on board.

    AC System new components are:

    New OE Condensor
    New Lines - Both
    New Accumulator Dryer


    Used but considered good parts:

    A/C Compressor - clutch engages if powered directly from Battery w/ pigtail
    Low pressure switch also called A/C Cycle switch in the service manuals - no change in systems if paper clip is used to bypass.
    High Pressure Switch on return line - no idea.

    On the power tour we tried to add freon without luck. At that time we discovered 0 voltage at the compressor also the condensor fan does not kick on with A/C. We were told IRCM as the culprit...I keep a spare in the glove box so that was changed out.

    I now have 8.8v at the compressor but it does not engage. If I manually engage the compressor with a pigtail to the battery it pulls the clutch in and runs.

    At this point my questions is first could someone who has AC tell me what voltage they have at the compressor? Should it really take 12 full volts to engage the clutch? Could I still have a bad IRCM? ...I have another spare I could try (figured I'd ask first).

    Stumped as to were to look next.

    -Tim
    Current Collection
    1994 Thunderbird SC - Auto converted to 5spd

    1995 Thunderbird SC - Auto

    1994 Thunderbird SC - 5spd
    1989 Thunderbird SC - 5spd - Daily Driver
    1990 Thunder/Cougar XR7 - 5spd
    1994 Thunderbird SC - 3v Project

  2. #2
    Join Date
    May 2012
    Location
    Denver Area
    Posts
    931
    If you can wait until Monday evening after I bring my Volt Ohm meter home from work I'm happy to check. I have a 94 SC with working A/C.

    One quick question - Where are you applying 12V? Right at C107?

    Name:  54-3 AC snippet.JPG
Views: 40
Size:  98.9 KB
    Last edited by potshotscott; 07-14-2018 at 03:28 PM. Reason: Added schematic

  3. #3
    Join Date
    Jan 2010
    Location
    Bossier City, LA
    Posts
    2,292
    Check the ground.

    It SHOULD be 12V more or less (by "more or less" I mean the system voltage isn't exactly 12V).

    Exact wiring varied from year to year, alas; my 1990 and 1993 EVTMs show different wiring for the non-EATC units. The 1990 doesn't show the EATC.

    My 1991 is "busy" at the moment (fancy for "It's in the pile on the bench, can't be arsed to double check there.")

    RwP

  4. #4
    Join Date
    Jul 2002
    Location
    Roanoke, Virginia
    Posts
    3,371
    Name:  20180714_103555.jpg
Views: 40
Size:  2.93 MB

    Yes right at c107 I have 8.8 ...picture should show how i just have a pigtail wired directly to the battery to make it engage...testing purposes obviously.

    Also waiting till Monday is fine. This car is just drove for ice cream on Friday nights. No rush, and appreciate the help.

    -Tim
    Last edited by Tim Groth; 07-14-2018 at 04:10 PM.
    Current Collection
    1994 Thunderbird SC - Auto converted to 5spd

    1995 Thunderbird SC - Auto

    1994 Thunderbird SC - 5spd
    1989 Thunderbird SC - 5spd - Daily Driver
    1990 Thunder/Cougar XR7 - 5spd
    1994 Thunderbird SC - 3v Project

  5. #5
    Join Date
    Jul 2002
    Location
    Roanoke, Virginia
    Posts
    3,371
    Quote Originally Posted by RalphP View Post
    Check the ground.

    RwP
    Do you know which one might be associated this the AC and I'll check it.

    -Tim
    Current Collection
    1994 Thunderbird SC - Auto converted to 5spd

    1995 Thunderbird SC - Auto

    1994 Thunderbird SC - 5spd
    1989 Thunderbird SC - 5spd - Daily Driver
    1990 Thunder/Cougar XR7 - 5spd
    1994 Thunderbird SC - 3v Project

  6. #6
    Join Date
    Jan 2010
    Location
    Bossier City, LA
    Posts
    2,292
    Quote Originally Posted by Tim Groth View Post
    Do you know which one might be associated this the AC and I'll check it.

    -Tim
    Here's the PDF of that particular page:

    1994_SC_AC_Clutch_Wiring.pdf

    RwP

  7. #7
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    7,379
    8.8v is your problem, and if you confirmed that reading direct from the connector to the battery, grounds aren't your issue. If ground was an issue, I'd expect other symptoms.

    A/C Clutch eventually grounds at G100, which is left hand side of IP, near steering column...meaning it grounds thru the switch, via the IRCM. However, it looks like there is a diode in the circuit between the IRCM and the clutch "taped to engine harness, near A/C clutch coil connector, 5.1" from A/C clutch coil".

Similar Threads

  1. How many SCs at your house?
    By Doug Franklin in forum Polls Forum
    Replies: 89
    Last Post: 04-25-2018, 09:33 PM
  2. How many CFMs does the stock throttlebody flow?
    By ssDurango in forum Technical Forum
    Replies: 2
    Last Post: 07-19-2007, 02:15 PM
  3. Quickly,, how many Qts does the M5R2 take??
    By splitportbird in forum Technical Forum
    Replies: 5
    Last Post: 12-01-2003, 04:13 PM
  4. Well how many gunna make the 16th???
    By GONE14S in forum Super Coupe Club of Northern California
    Replies: 4
    Last Post: 09-12-2001, 06:14 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •