[Main C900 Bulletin Board | BBFAQ | Prev by Date | Next by Date | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos Re: no tach signal at LH conn./why?... Like This Post: - Subscribe to Daily Digest for this Bulletin Board Posted by Justin VanAbrahams [Email] (#32) [Profile/Gallery] (more from Justin VanAbrahams) on Wed, 24 Oct 2001 20:34:33 In Reply to: no tach signal at LH conn./why?..., Ed S, Wed, 24 Oct 2001 20:22:06 Alert me when someone posts in this thread: Members do not see ads below this line. - Help Keep This Site Online - Signup

There could be four reasons:

1. The Hall-Effect sensor is dead - you can test this as per the Bentley manual
2. The Ignition Control Unit (ICU) is dead - again, you can test this as per Bentley.
3. The Ignition Pulse Amplifier Relay is dead, but you shouldn't have one on an '85. :)
4. The wiring between these components is dead - on an '85, I would not be surprised.

Start at the ICU. Unbolt the ICU from the fender and pull it up. Pull the boot off the back of the connector. Connect your DMM to the appropriate pins (it's in Bentley) BUT DO NOT unplug the connector - enter it from the, uh, rear. Have someone turn the engine over and test for voltage (4VDC, IIRC). If you get that, check the tach output signal from the ICU - it's in the Bentley. If you don't get 4VDC (again, IIRC) here you've got a dead ICU. My money is on this component.... Hall Senders rarely die IME (though the wiring does). You can get a replacement from ANY 900T I believe, so there are tons out there. If you do get signal here, you've got a break somewhere between this little bugger and your ECU. Another test point is at the instrument cluster, but this one is hard to get to. You can look in the Bentley for the right pin to test on the cluster - you should be able to access it through the speaker grille.

Let me know how this goes...

-Justin

posted by 64.164.3...

• no tach signal at LH conn./why?..., Ed S, Wed, 24 Oct 2001 20:22:06
  • Re: no tach signal at LH conn./why?..., wade taylor, Thu, 25 Oct 2001 00:40:15
  • Re: no tach signal at LH conn./why?..., Justin VanAbrahams , Wed, 24 Oct 2001 20:34:33 <-- Viewing This Message
    • not good....., Ed S, Wed, 24 Oct 2001 23:50:57
      • correction, tach. signal good......, Ed S, Thu, 25 Oct 2001 00:40:31

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