Results 1 to 5 of 5

Thread: Tachometer Woes

  1. #1
    Senior Member
    Join Date
    Jul 2012
    Location
    Kentucky
    Posts
    111

    Tachometer Woes

    Hello all, I am finally trying to diagnose the problem with the tachometer on my 1974 SR5 Corolla. Unfortunately, both of the shop manuals I have just skip over the tachometer entirely and assume that the car is equipped with just a speedo and multi gauge. I understand somewhat the theory of how an electronic tach works, but I cannot wrap my head around diagnosis of my actual system. The issue is that when I turn the key to the "on" position (not starting the car), the tach pegs at 8k. It remains that way once started and running. This seems to be indicative of a very simple problem in the electrics, but I do not know what that problem is. Does anyone have any suggestions?

  2. #2
    Senior Member
    Join Date
    Feb 2008
    Location
    Saratoga N.Y.
    Posts
    729

    Re: Tachometer Woes

    Im no help but I think my 77 te51 had this problem also??

    If the cluster is out of the dash,check the back of it,the plastic grid wiring could be damaged and bad ground somewhere??

  3. #3
    Senior Member
    Join Date
    Jul 2012
    Location
    Kentucky
    Posts
    111

    Re: Tachometer Woes

    The wiring behind the gauge cluster looks good, but I did notice something tracing the wire from the tachometer to under the hood. It runs from the tach to the distributer, where it is also tied in to a condenser. In my mind, this has to be the problem. Does the tach not read the rapid charging/discharging of the condenser in order to tell RPM? The condenser looks ancient, and is clearly in disrepair. The next task is actually finding another to replace it with. I don't have a part number for it, and the markings on the bottom are almost totally illegible. I assume any 12V condenser will work in its stead?

  4. #4
    Senior Member
    Join Date
    Feb 2008
    Location
    Saratoga N.Y.
    Posts
    729

    Re: Tachometer Woes

    Try it without the condenser :idea:
    Its probably something simple but overlooked??

  5. #5
    Senior Member
    Join Date
    May 2009
    Location
    Melbourne Australia
    Posts
    274

    Re: Tachometer Woes

    Verbatim from the factory body manual.

    "The engine tachometer utilised on the model S indicates the engine revolution by actuating the direct current ammeter with the pulsation created during the opening and closing of the distributor points which is applied as transistor signal to charge the condensor provided on this output side, and the discharge current functions the movement."

    Well yes, whatever. Other than checking the connections at coil, I would have to think the tacho itself may be suspect.

    The condensor is not actually doing anything when you turn the ignition to On, without the engine started.

    The Bosch part number for a 2T condensor is GD209

Similar Threads

  1. Sidedraft woes..
    By oldisgold in forum Mazda Garage
    Replies: 27
    Last Post: 07-04-2013, 10:10 PM
  2. WTB - Datsun 510 Tachometer
    By nakaz_510 in forum Datsun/Nissan Swap Meet
    Replies: 0
    Last Post: 07-21-2012, 05:30 PM
  3. 5mge bogging woes, jnc gods chime in please
    By Eightythree in forum Toyota Garage
    Replies: 17
    Last Post: 07-10-2011, 07:38 AM
  4. need help.. as always LOL KGC10 harness woes
    By wookieballa in forum Datsun/Nissan Garage
    Replies: 4
    Last Post: 05-25-2011, 10:08 PM
  5. Subaru 360 Van tachometer test
    By 2stroketurbo in forum Subaru Garage
    Replies: 0
    Last Post: 04-02-2010, 11:47 PM

Posting Permissions

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