Results 1 to 21 of 21

Thread: a/c blows cold but.....

  1. #1

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64

    a/c blows cold but.....

    I have to hot wire clutch. So no 12v to clutch, Freon is all in check so good there and I'm getting 12v at the relay, but only 2.7 volts to the low pressure switch. I also checked volts at the a/c switch connecter on dash, nothin. Anyway to check the a/c module, that's the black box under evap case right? I heard there a bit delicate? It's kind of funny, I found a trail of evidence where the last technition hunted on the same path as me, but broke every little plastic tap/clip along the way.... Any other ideas

  2. #2

    Array
    Status
    Offline
    Join Date
    04-06-2011
    Posts
    482
    Location

    Jacksonville, FL
    Vehicle

    1990 Mitsubishi Mighty Max
    Engine

    G54B-T
    You should have 12 volts at the a/c switch on the dash. The 12 volts comes from the blower switch. Did you check for power with the blower motor on?

  3. #3

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64
    Quote Originally Posted by crvtec90 View Post
    You should have 12 volts at the a/c switch on the dash. The 12 volts comes from the blower switch. Did you check for power with the blower motor on?
    Okay, I do have 13 volts at the a/c switch and 12v at the controller (black box under evap case) from thermister

  4. #4



    Array
    Status
    Offline
    Join Date
    03-16-2011
    Posts
    3,803
    Location

    Sacramento, CA
    Vehicle

    1979 Dodge D-50
    Engine

    Chevy V6
    You must have a bad connection with lots of dirt or oil on somthing. I think we have a manual with the electrical system on your truck. In the manual; section under 216 manuals. look for the pick up and montero book. I think there is one in it.

    Do you have 12V on both sides of the AC button?
    Members come and members go, But the board keeps track of them.
    Find me on FaceBook
    clicking HERE.

    Or look on YouTube Click Here.
    http://mobilemillwright.com

  5. #5

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64
    Quote Originally Posted by camoit View Post
    You must have a bad connection with lots of dirt or oil on somthing. I think we have a manual with the electrical system on your truck. In the manual; section under 216 manuals. look for the pick up and montero book. I think there is one in it.

    Do you have 12V on both sides of the AC button?
    Only one wire going to the switch has the 13v. My Haynes book only goes up to 93' (wiring is a bit different than what's in my car) but I just bought a factory manual that goes up to 96' ....so hopefully that will help some.

  6. #6



    Array
    Status
    Offline
    Join Date
    03-16-2011
    Posts
    3,803
    Location

    Sacramento, CA
    Vehicle

    1979 Dodge D-50
    Engine

    Chevy V6
    There should be a relay between the Thermostat and the clutch. Look there for the voltage drop.
    Members come and members go, But the board keeps track of them.
    Find me on FaceBook
    clicking HERE.

    Or look on YouTube Click Here.
    http://mobilemillwright.com

  7. #7

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64
    yes the voltage drop is there, 1 terminal has 14.4ish when running and a/c switch on and the terminal from the low pressure switch & coolant temp sensor (black w/yello strip) has 2.7 v

  8. #8



    Array
    Status
    Offline
    Join Date
    03-16-2011
    Posts
    3,803
    Location

    Sacramento, CA
    Vehicle

    1979 Dodge D-50
    Engine

    Chevy V6
    OK now you need to fallow the low voltage back to where it goes back up. There you will find the problem. There should be no drop in the system.
    Members come and members go, But the board keeps track of them.
    Find me on FaceBook
    clicking HERE.

    Or look on YouTube Click Here.
    http://mobilemillwright.com

  9. #9

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64
    Well I did some checking today, the wire with the 2.7 volts (according to my 93' Haynes manual) travels to the a/c thermostat (but my truck is a 95') so my truck has a MD630306 controller. So I'm thinking this is where the problem lies. Can't wait to get the new manual..any thoughts on "that" black box?

  10. #10



    Array
    Status
    Offline
    Join Date
    03-16-2011
    Posts
    3,803
    Location

    Sacramento, CA
    Vehicle

    1979 Dodge D-50
    Engine

    Chevy V6
    sent you a PM with link to manuals you can use.
    Members come and members go, But the board keeps track of them.
    Find me on FaceBook
    clicking HERE.

    Or look on YouTube Click Here.
    http://mobilemillwright.com

  11. #11

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64
    Received my manual today...WOW, this thing is awesome, a lot better than the Haynes...anyway I found the problem, it's in the black a/c controller, if I jump the 12v (blue w/red stripe) to the 2.7 v (black w/yellow stripe) at the controller (unhooked) the compressor clutch works as it should, complete control with blower switch and a/c switch. I guess what doesn't work is the thermostat area of the unit. Anyone with a black box they'll sell?
    Attached Images

  12. #12



    Array
    Status
    Offline
    Join Date
    03-16-2011
    Posts
    3,803
    Location

    Sacramento, CA
    Vehicle

    1979 Dodge D-50
    Engine

    Chevy V6
    Can you scan in your manual to PDF? If so then you can send it to me and I can drop it on the board for everyone. Only if you want to. The bad thing is you need to cut the book up so you can run it through the scanner. It took me about 4 hours to do my first gen manual.
    Members come and members go, But the board keeps track of them.
    Find me on FaceBook
    clicking HERE.

    Or look on YouTube Click Here.
    http://mobilemillwright.com

  13. #13

    Array
    Status
    Offline
    Join Date
    10-12-2012
    Posts
    114
    Location

    Lawton, OK
    Vehicle

    1980 Dodge Ram 50
    Engine

    Chevy V8
    Im not sure exactly how your HVAC wiring is laid out but usually there is the high side pressure switch and the low side pressure switch between the pcm and the relay. they are normally closed circuits so if pressure gets too high on either side it will open the circuit, there by cutting power to the relay. So in other words you may have a short in your pcm or one of your pressure switches is faulty. But again, i dont know how it is on an older truck.

  14. #14

    Array
    Status
    Offline
    Join Date
    10-12-2012
    Posts
    114
    Location

    Lawton, OK
    Vehicle

    1980 Dodge Ram 50
    Engine

    Chevy V8
    Im not sure exactly how your HVAC wiring is laid out but usually there is the high side pressure switch and the low side pressure switch between the pcm and the relay. they are normally closed circuits so if pressure gets too high on either side it will open the circuit, there by cutting power to the relay. So in other words you may have a short in your pcm or one of your pressure switches is faulty. Also it may be your Ambient Temperature sensor. But again, i dont know how it is on an older truck.

  15. #15

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64
    Quote Originally Posted by DOPRIUS View Post
    Im not sure exactly how your HVAC wiring is laid out but usually there is the high side pressure switch and the low side pressure switch between the pcm and the relay. they are normally closed circuits so if pressure gets too high on either side it will open the circuit, there by cutting power to the relay. So in other words you may have a short in your pcm or one of your pressure switches is faulty. Also it may be your Ambient Temperature sensor. But again, i dont know how it is on an older truck.
    It has a dual pressure switch, which I jumped...didn't make a difference?

  16. #16

    Array
    Status
    Offline
    Join Date
    10-12-2012
    Posts
    114
    Location

    Lawton, OK
    Vehicle

    1980 Dodge Ram 50
    Engine

    Chevy V8
    Whats the volts to the first pressure switch?

  17. #17

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64
    it only has one switch, a dual pressure....2.7 volts

  18. #18

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64
    The dual pressure switch on the lower left side
    Attached Images

  19. #19

    Array
    Status
    Offline
    Join Date
    10-12-2012
    Posts
    114
    Location

    Lawton, OK
    Vehicle

    1980 Dodge Ram 50
    Engine

    Chevy V8
    Sounds like a short in your pcm. Or you may have a bad relay.nhaveyou checked the relay?

  20. #20

    Array
    Status
    Offline
    Join Date
    10-12-2012
    Posts
    114
    Location

    Lawton, OK
    Vehicle

    1980 Dodge Ram 50
    Engine

    Chevy V8
    Jump 12v across the relay to the press. switch and see if your gettin 12v

  21. #21

    Array
    Status
    Offline
    Join Date
    08-25-2012
    Posts
    160
    Location

    Winter Park, FL
    Vehicle

    1994 Mitsubishi Mighty Max
    Engine

    4G64
    Quote Originally Posted by DOPRIUS View Post
    Sounds like a short in your pcm. Or you may have a bad relay.nhaveyou checked the relay?
    Well I'm getting 12v at the relay, also I'm getting 2.7 volts at the relay (all with the relay disconnected) So my thinking is it's not the relay if I'm getting 2.7 volts there without it being connected. Short in the PCM? It does connect to the other side of the low pressure switch, but the 2.7v is comming from the controller side of the a/c circuit not the PCM....Please correct me if I'm wrong?

Tags for this Thread

Bookmarks

Bookmarks

Posting Permissions

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