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Thread: HVAC lights flickering

  1. #1
    E500E Guru Melville's Avatar
    Join Date
    Oct 2012
    Washington DC

    HVAC lights flickering

    Lately Iíve noticed my HVAC and ashtray lights flicker sometimes when Iím driving with headlights on. Itís just those lights ó the top row of lights in the console are fine, as are the window and seat heater etc. lights in the center console between the seats. I drive so rarely with headlights that Iím not sure when this might have happened.

    Some possibly relevant facts:
    - I switched the bulbs to LED a while ago. It was some time after doing the switch that I first noticed the problem, but as mentioned I donít drive with headlights often so donít know when it started.
    - A little while ago I removed my console wood for refinishing. After putting everything back together again, I discovered I didnít re-connect some wires deep behind the ashtray and wasnít getting power there. I reconnected it (with much knuckle-scraping and cursing). But I wonder if I loosened a ground wire or something.

    Any thoughts?

  2. The Following User Says Thank You to Melville For This Useful Post:

    TerryA (11-23-2017)

  3. #2
    E500E Guru nocfn's Avatar
    Join Date
    Jan 2014
    Kingwood TX

    Re: HVAC lights flickering

    turn lights on in the darkness or in the garage, rotate the rheostat on the left cluster to see if the connection improves.
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

    1991 560 SEC
    2014 E350 Cab 799/264

  4. The Following 2 Users Say Thank You to nocfn For This Useful Post:

    Melville (11-23-2017), TerryA (11-23-2017)

  5. #3
    Site Honcho
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    gerryvz's Avatar
    Join Date
    Nov 2008
    Annapolis, MD

    Re: HVAC lights flickering

    Rheostats are generally more of an "on" or "off" prospect when not making good contact, not a flicker. Furthermore, the rheostat controls pretty much ALL of the dash/instrument lighting, not just the HVAC panel. Thus, while not a bad idea to tweak the rheostat a few times a year by running it rapidly back and forth, it is NOT the problem for what Melville is experiencing.

    It is very likely that one of the connectors to the back of your HVAC panels that supplies power to the lights, is loose or making partial contact.

    Remove the center console wood, and pull the HVAC controls. Pull the two large connectors to the back of the HVAC controls, and any other connectors there (I think there is one, and then one going down to the ashtray area. Inspect the contacts at both the connector and the control unit, and make sure there is good and clean contacts made. Use alcohol or contact cleaner if desired.

    Push the connectors back onto the HVAC control tightly, and reconnect any other connectors.

    Definitely check the integrity of your grounds, as well, under the center console.

    Hopefully this takes care of your problem.

    If not, then it is probably related to your LED bulb retrofit, and I recommend going back to the traditional incandescent bulbs.


  6. The Following 3 Users Say Thank You to gerryvz For This Useful Post:

    Melville (11-23-2017), nocfn (11-23-2017), TerryA (11-23-2017)

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