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Old Apr 15, 2020 | 03:08 PM
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GavsST170
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Joined: Apr 2020
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From: Buckingham
Default ST170 IMRC "different" problem

Hi. Yes, more IMRC issues! I have an issue that is slightly different from most.
After getting fault codes, I dismantled my system:
  • Mechanically, the flaps work fine.
  • I dismantled the IMRC servo unit, checked it, cleaned it, and re-assembled it.
  • I cleaned and lubricated the control cable
  • Re-assembled the whole system.
Now, when I start the engine the cable pulls the flaps open, and switching off releases them. However, with the engine running, the flaps do not release at 5000rpm, but only when it reaches just over 7000rpm, which is probably when the rev limiter activates. So in summary, the complete system all works fine except the IMRC doesn't respond to the rpm. I didn't replace the transistor, but would this be responsible for this issue? Does anyone know how the IMRC gets the rpm change signal and can I check this on 1 of the wires on the IMRC plug, or elsewhere?

Thanks for your interest.
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