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Thread: 1990 SC IRCM pinout and schematic pdf?

  1. #1
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    1990 SC IRCM pinout and schematic pdf?

    Does anyone have a pdf or image of a 89 and 90 IRCM pinout and schematic?


    My radiator fan will not turn on so i am considering trying to find and replace the bad relay in the ICRM


    Someone previously posted the info for a 93 IRCM but i believe that was different?


    Thanks in advance.


    icrm, relay module, cooling fan

  2. #2
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    I believe this is for '89 ~ '90.

    Just be aware that unless you're comfortable w/board level repairs, you might want to find another IRCM, instead.

    A quick way to test the IRCM is to attach a code reader and run a KOEO test...the fan should hit both speeds in very rapid succession, then turn off. As well, be sure to disconnect the harness at the fan, and jumper both speeds as a sanity check on the motor itself. I had a fan issue and thought it was the IRCM but it turned out to be the connector at the fan.

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  3. #3
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    Quote Originally Posted by KMT View Post
    I believe this is for '89 ~ '90.

    Just be aware that unless you're comfortable w/board level repairs, you might want to find another IRCM, instead.

    A quick way to test the IRCM is to attach a code reader and run a KOEO test...the fan should hit both speeds in very rapid succession, then turn off. As well, be sure to disconnect the harness at the fan, and jumper both speeds as a sanity check on the motor itself. I had a fan issue and thought it was the IRCM but it turned out to be the connector at the fan.

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    Thank you!

    Yes i am attempting a board-level repair. Will have to see if the bad transistor or relays can be obtained. My low speed relay does not click currently.
    Last edited by GAR; 08-28-2016 at 07:09 PM.

  4. #4
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    Resurrecting an old thread I know but hoping that you can update us on your board level repair attempt. I've got a similar rad fan problem in that mine doesn't run unless I turn on the AC. Not a problem in winter but it's driving temperatures up in the winter.

    Did you ever replace the relays? Take any photos?

  5. #5
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    i attempted this repair a while back and failed. it should be possible though...

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    I used DigiKey PN: PB1039-ND as replacements. They are 12V 40A SPST PCB mount automotive relays. Pretty sure that is a compatible part as the original is no longer available.

    I lifted a trace from the board trying to remove the old relays. the conformal coating is a pain. Not sure if thats what killed it or not, but it didnt work right when i reinstalled it.
    Any idiot can make a Mustang fast...
    It takes a special idiot to make a Thunderbird fast!!!
    89 SC 4.3 stroker 384rwhp 473ftlbs
    Best ET 13.085 Best MPH 106.6... got some work to do!
    2016 V6 M90 Dyno Champ 2016 Mod 1 Runner Up

  6. #6
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    Quote Originally Posted by potshotscott View Post
    I've got a similar rad fan problem in that mine doesn't run unless I turn on the AC. Not a problem in winter but it's driving temperatures up in the winter.
    Did you test w/a code reader IRCM to confirm it is the culprit? Last time I had a similar issue, it was that the main connector at the fan wasn't fully seated - someone in the past had broken the keepers and it was held together w/a zip tie that relaxed over time, which I found when I went to power the fan circuits directly to confirm it's health.

    Another time it was that the IRCM bolt was loose and the ground path wasn't reliable.

    Point is, don't assume it's a failed IRCM every time I had at least two IRCMs I thought were bad that turned out to be fine once I learned how to test properly.

    Ken

  7. #7
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    Wink

    Really good point Ken. I don't have any codes that suggest IRCM (just EGR ). I did have the radiator out of the car a year or two ago to have the tank soldered on. Have to check the connection one more time.

  8. #8
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    dthompson - do you have a photo of the trace you lifted? I do a LOT of soldering and have done *some* board repair before.

  9. #9
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    it could be that the low speed relay is bad... when the AC is on, isnt that the high speed fan? I cant remember, and I dont know for sure, so take that as an idea, not a fact. The low speed fan relay gets a lot more use. mine low speed relay contactor looked a lot worse than the high speed one.
    Any idiot can make a Mustang fast...
    It takes a special idiot to make a Thunderbird fast!!!
    89 SC 4.3 stroker 384rwhp 473ftlbs
    Best ET 13.085 Best MPH 106.6... got some work to do!
    2016 V6 M90 Dyno Champ 2016 Mod 1 Runner Up

  10. #10
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    Quote Originally Posted by potshotscott View Post
    dthompson - do you have a photo of the trace you lifted? I do a LOT of soldering and have done *some* board repair before.
    no i dont think so. but you have to desolder the relay from the back side of the board. If you dont get it all, and you pull on the relay to remove it, it can lift the pad or the whole trace on the top side. The trace didnt tear, but about inch separated from the board.
    Any idiot can make a Mustang fast...
    It takes a special idiot to make a Thunderbird fast!!!
    89 SC 4.3 stroker 384rwhp 473ftlbs
    Best ET 13.085 Best MPH 106.6... got some work to do!
    2016 V6 M90 Dyno Champ 2016 Mod 1 Runner Up

  11. #11
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    I can confirm that it is very easy to lift/damage a trace on these boards

    Pretty sure they were originally wave soldered. Manual repairs of this type are difficult enough, but that much harder when the components are this old and have been in service with years of heat cycles, etc.

    Many Fords used these types IRCMs - I've been studying late model Windstars to see if they can be donors. On that note, it might be they use the same brake pressure switch too, but I'll have to buy one to find out. Not bad, around $40 new, I think.

    And one final note on troubleshooting - I keep known working spares now, and just swap them in to see if the in-service unit is acting out, or if the issue lurks elsewhere.
    Last edited by KMT; 02-21-2017 at 09:17 PM.

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