Good ground?

Discussion in 'General Electronics Chat' started by New2electronics, Oct 9, 2011.

  1. New2electronics

    Thread Starter New Member

    Oct 6, 2011
    2
    0
    Hello everyone, I'm new to the field of electronics. I'm currently studying for
    An associates in engineering. I figure this site will expand my learning experience in the fundamentals. At the moment I am in the middle of an issue.
    I'm working on a car, and I'm suspecting that it has an issue with good source of ground. Is there any way I can test this out? Will I have to consider the resistance of the car as a whole? Any input will be appreciated thanks..
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,388
    1,605
    Well... first off, automotive applications are not allowed on this board, so expect your thread to be closed shortly.

    But generally the car chassis is an excellent ground for power, not so good for signals like say audio or a digital bit stream.

    I was fooled once installing an audio power booster due to my dash being all plastic and it was making ground thru an audio connector. It would still light up as if it would work, but never made a peep till I got that settled.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Actually, it's automotive modification topics that are restricted. I don't see any problems with having discussions like this, as long as the vehicle in question is being repaired to function as it did originally using original parts, rather than modifying anything.

    Ground connections frequently get corroded on older vehicles; you have to track them down and use a wire brush, sandpaper or something similar to clean the connection up - after connecting it again, use grease or some other covering to keep air & fluids away from it.
     
  4. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    Well, in that case, how old is "old"? With a 1955 Chevy Belair or a 1973 Ford Econoline, you can always grind a clean spot on an I beam and use that for a ground. You can test alleged grounds with a long wire and an ohm meter. On newer old cars, you might have to run a seperate (redundant) ground wire to get something dependable.
     
  5. New2electronics

    Thread Starter New Member

    Oct 6, 2011
    2
    0
    I apologize for the inconvenience, I'm still getting used to this forum. In actuality
    My car is a late 80's model. Only reason I'm thinking ground is because majority of time when I go to turn the ignition the starter would click (as a dead battery) but eventually after some time of trying the key the starter gear will engage. I'm pretty sure the starter is good. All connections between the battery and starter seem in good condition. Any ideas what else I could do than just cleaning off the grounding points.
     
  6. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    The last time I looked, a battery ground cable is attached directly from the battery terminal to the engine block and that's the current ground for the starter motor. That is a short distance to trace out and prove compared to a tail light! It's one wire, it's fat, and it's held on with a bolt.

    Then check the red wire from the battery to the starter solenoid. End of list.

    If those wires have no problem, "pretty sure" is going to have to be checked out properly. My crystal ball shows that you are in the U.S.A. so you can go to an auto parts store and get a free check on the battery/alternator/starter system.
     
  7. Lundwall_Paul

    Member

    Oct 18, 2011
    220
    19
    Use a jumper cable connected directly to the
    Negative post of the battery connect the other end of the jumper cable to the frame of the starter or the negative post of the starter. If it now works you do indeed have a bad ground in your car.
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,789
    945
    If the cable is as old as the car, replacement might be called for. The exterior(visible) portions of the cable connections are not the only place oxidation and corrosion can appear. The INSIDE of the cable and of the terminals, where the bare copper is inserted and crimped can become corroded as well.
    Try the jumper cable suggestion, and if the starter instantly engages, add 'bad ground cable' to the list of possible problems.
     
  9. Mike33

    AAC Fanatic!

    Feb 4, 2005
    349
    25
    Just for grins (since most likely it IS a bad ground), sometimes a starter will also have 1) teeth that are chewed so don't always engage the flywheel or 2) don't 'throw out' the way they're supposed to - some have to pop out, engage, and then pop back after the flywheel turns, car starts, and you release the switch. In bad cases, it's the FLYWHEEL itself that is chewed, from engaging the starter with the motor running....

    That's why sometimes, people tap on a starter with a small hammer/wrench, etc. - to break the internal corrosion free so it will engage again (until it dies for real!).
    So, if it's not a ground or other electrical connection, get a rebuilt starter and throw it in; shouldn't be much trouble, 2-3 bolts and the wires. Hardest part is getting around in the dang engine compartment!! :mad:
    How do I know? '93 Toyota 4x4, 22RE :D
     
  10. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Apart from the obvious problems of a near-dead battery or faulty starter, the merest smidgen of contact resistance at the battery terminals may be fatal to the chance of starting. The cranking current being as much as hundreds of amps, only a tiny resistance is needed to give a problem. Battery connections must be clean and tight.
     
  11. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    Guys...this is an old thread.
     
  12. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,388
    1,605
    It could be the starter solenoid. Sounds just like a bad battery. My truck had a bad one, at first it usually started. Sometimes it took a few tries. Eventually it took lots of tries. The last time I started it it took over 200 tries.

    I left it running as I checked it into the shop and the shop guy thanked me for that.
     
  13. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Meh - 11 days isn't that old.

    And really, this is the time of year where it seems that auto batteries "suddenly go dead" in the northern hemisphere - where they seemed OK during the warmer summer weather. Now that the battery core temperature is decreased, so is the cranking capacity. The colder it gets, the harder it will be to start the engine.
     
  14. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    It's easy to forget that in Florida.
    I'm just beginning to feel frisky now that the heat index is below 80!
    Did the semi-annual fluid refills today...never even thought about the battery getting cranky.
     
Loading...