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  • Using a Multi-Meter

    Anyone have a clue how to use a Mult-meter to trouble shoot automotive issues?

    I know I know...... I have a book and google. Just hoping someone can put it in english.
    Last edited by BadOrderKing; 08-31-2010, 12:46 AM.
    All postings by BadOrderKing are public information, works of fiction, sometimes resembling the rants of a madman and in no way should be construed to represent the positions, views, or thoughts of any particular railroad carrier. No one listens to him anyway.


  • #2
    Wow you going back to the ol days.....:shocked:...I think the Army trained me on those and the low voltage circuit testers...So what you are basically trying to do is check the continuity of the wires, votls/amps....But that was back in the 70's lol..

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    • #3
      Originally posted by ghostrider View Post
      Wow you going back to the ol days.....:shocked:...I think the Army trained me on those and the low voltage circuit testers...So what you are basically trying to do is check the continuity of the wires, votls/amps....But that was back in the 70's lol..
      Well I have already replaced my battery twice in the past year, had my alternator rebuilt and am having some more issues now. Something is killing my batteries.

      Anyhow, in the past couple weeks my car has been acting up at idle and even dying when I turn on the a/c at a light. I assumed an idler control sensor or something, but the other day the battery was dead. I jumped it off and it ran fine. I took the neg cable off the battery and it ran fine. Turned the car off for a minute and the battery was dead again.

      Something aint right. So i bought me a multi-tester and am blindly attempting to diagnose the problem.
      All postings by BadOrderKing are public information, works of fiction, sometimes resembling the rants of a madman and in no way should be construed to represent the positions, views, or thoughts of any particular railroad carrier. No one listens to him anyway.

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      • #4
        Originally posted by BadOrderKing View Post
        Well I have already replaced my battery twice in the past year, had my alternator rebuilt and am having some more issues now. Something is killing my batteries.

        Anyhow, in the past couple weeks my car has been acting up at idle and even dying when I turn on the a/c at a light. I assumed an idler control sensor or something, but the other day the battery was dead. I jumped it off and it ran fine. I took the neg cable off the battery and it ran fine. Turned the car off for a minute and the battery was dead again.

        Something aint right. So i bought me a multi-tester and am blindly attempting to diagnose the problem.
        year of car, model and engine, ? My first hunch is probably what you have already checked, a grounded out system? Hence is the reason you have been asking about the multi meter. Any bad cables that may be shorting into each other and crossing the ground, and or routing a ground to he frame. Have you looked under your hood at night or in the dark to see if you can see any sparks? Hot wires? As for the ac being turned on, you have a weak electrical system and I believe ac;s can sometimes draw up to a 30% drain on the hp, which could be caused by low freon, bad pulley. You bought 2 new battery's in a year, what about warranty replacement and could it be your first battery went bad and you bought one which also is a factory defeted one and won't keep a charge?

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        • #5
          Originally posted by ghostrider View Post
          year of car, model and engine, ? My first hunch is probably what you have already checked, a grounded out system? Hence is the reason you have been asking about the multi meter. Any bad cables that may be shorting into each other and crossing the ground, and or routing a ground to he frame. Have you looked under your hood at night or in the dark to see if you can see any sparks? Hot wires? As for the ac being turned on, you have a weak electrical system and I believe ac;s can sometimes draw up to a 30% drain on the hp, which could be caused by low freon, bad pulley. You bought 2 new battery's in a year, what about warranty replacement and could it be your first battery went bad and you bought one which also is a factory defeted one and won't keep a charge?
          03' Ford Taurus V6

          Yeah, the first time I bought a new battery. The next one was a warranty replacement.

          Have not tried the night time thing. Until yesterday, I had no reason to suspect the electrical system. Thought it was a sensor until I had another dead battery.

          I picked up the multi-meter tonight since half the topics i Googled called for one. However, I really have no idea how to set the thing to even begin.
          All postings by BadOrderKing are public information, works of fiction, sometimes resembling the rants of a madman and in no way should be construed to represent the positions, views, or thoughts of any particular railroad carrier. No one listens to him anyway.

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          • #6
            If you have a voltage draw constantly, like a relay somewhere that is stuck closed, it would drain the battery.

            One way to isolate a circuit draw easily would be the following steps.

            1. Disconnect a battery cable and read the voltage across the terminals, write this down.

            2. Re-connect the battery cables then read the voltage across the terminals, if it has dropped, then there is a draw against the battery, ie current flow. Voltage drops with current flow.

            3. Go to the fuse panel, and pull one fuse at a time till the voltage drop goes away. That can isolate one individual circuit to see if a relay somewhere is shorted, ie contacts not opening.

            Now, on new vechicles, and I have no idea what that electrical schematic looks like, many things are black box, and the above test may not be conclusive, but it is where I would start,.
            Only 511 ft lbs of Tq and only 1100 degrees EGT, damn, I need more fuel...

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            • #7
              one other thing, the only AC power is at the alternator, internal before the voltage rectifier, all other power will be read in DC volt settings, referenced to chassis ground.

              You can take the battery and alternator in to most auto parts stores, like NAPA or Autozone, and they can bench test them.

              It might also be as simple as an alternator thats not charging the correct voltage and the normal draw from the car drains it. If I were doing it myself I would rule out those 2 items first.

              There is always a minute draw for radio presets and clock, ECM takes a tiny bit as well, but nowhere near enough to drain a battery overnight.

              Just my opinions, take it with a grain of salt.

              One other tidbit, be carefull while Tshooting, even though it is a 12VDC system, if the positive side of any terminal shorts to ground, it will arc, burn things up etc.
              Only 511 ft lbs of Tq and only 1100 degrees EGT, damn, I need more fuel...

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              • #8
                With all the electrical goodies in cars the days, a heavy duty alternator is de rigeur. If you perchance don't have one, do see that your replacement is one.
                sigpic ΜΟΛΩΝ ΛΑΒΕ "Come and get them" Leonidas I to Xerxes, at Battle of Thermopylae

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                • #9
                  OK this is what I got this morning. I tested both my truck and my car.

                  TRUCK:

                  off - 12.61
                  on - 14.24
                  a/c on - jumped up and down 14.00 - 14.27


                  CAR:

                  off - 10.12
                  off w/jumper cables - 13.87
                  on - 14.50
                  a/c on - Jumped up and down 14.11 - 14.37
                  @2000 rpm - steady 14.40 (with and without a/c)

                  Two things were very noticeable;

                  1. Weird whine in alternator.

                  2. When I tunred the car off and kept the metrer on the battery, The voltage went downward resembling a backwards running clock. ook about two minutes for it to reach uncrankable levels and remains steady at 10.20

                  Alright.... gotta run pay some bills. Be back later. Hope some of this makes sense.
                  All postings by BadOrderKing are public information, works of fiction, sometimes resembling the rants of a madman and in no way should be construed to represent the positions, views, or thoughts of any particular railroad carrier. No one listens to him anyway.

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                  • #10
                    my take,

                    If there is a draw, and that is what that tells me, the volatge is dropping because something is shorted to ground.

                    If you load test the alternator and battery, a cheap non expense, just your time, then do the fuse pull route.
                    Only 511 ft lbs of Tq and only 1100 degrees EGT, damn, I need more fuel...

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                    • #11
                      Well I tried the one thing that I forgot to do earlier. I took the cables of the battery and read the voltage and again after 10 minutes. Even without the cables it wil only hold about a 10 v charge. Took it back to store and sure enough, bad cell. New battery in car and THAT part is licked.

                      I am back to square one on my car acting crappy. Went to Autozone and the found two codes. Both point to the car running lean. Misfires on bank 1. I dont doubt a vacuum leak since my wiper washer hose crumbled about a year ago.

                      HERE I GO AGAIN!!!
                      All postings by BadOrderKing are public information, works of fiction, sometimes resembling the rants of a madman and in no way should be construed to represent the positions, views, or thoughts of any particular railroad carrier. No one listens to him anyway.

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                      • #12
                        You can count on rubber hoses to work well about 5 years, after that you are biding your time. Good luck with the electrical gremlin.
                        sigpic ΜΟΛΩΝ ΛΑΒΕ "Come and get them" Leonidas I to Xerxes, at Battle of Thermopylae

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                        • #13
                          Originally posted by jonnyseeandoh View Post
                          You can count on rubber hoses to work well about 5 years, after that you are biding your time. Good luck with the electrical gremlin.
                          Yeah, the codes are be set of by the O2 sensor reading lean output from the number 1. I THINK that is what I am understanding.

                          Trying to give the car time to cool off before I go poking and proding in there. This will sure be a gremlin and I can only imagine what taking it to a qualified mechanic would cost.

                          EDIT: There is still a few electrical issues that need attention so the multi-meter was a worthwhile investment
                          All postings by BadOrderKing are public information, works of fiction, sometimes resembling the rants of a madman and in no way should be construed to represent the positions, views, or thoughts of any particular railroad carrier. No one listens to him anyway.

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                          • #14
                            As old a the car is the O2 sensor itself could be toast....and worth replacing as a matter of course....also clean the idle air control pintle, and consider the throttle position sensor though they are pretty reliable on Fords. Just some ideas...I'd lean hard on that O2 sensor at present.
                            sigpic ΜΟΛΩΝ ΛΑΒΕ "Come and get them" Leonidas I to Xerxes, at Battle of Thermopylae

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                            • #15
                              Originally posted by nsguy
                              Check out the "Taurus Car Club of America" web site! Lotsa info there! Which engine do you have? Vulcan or Duratech? Shouldn't make a difference regarding an electrical problem though. Just rolled 145K last week on my '98 DOHC Tech. I don't care if it costs me 10 G's but this is the car I WILL get over the 200,000 mile mark!!! Just wanna do it once in my lifetime!
                              Not real sure. As I type this I am drawing a blank as to how many valves the damn thing has. I will just say Vulcan.

                              I think I have hit on that site a few times when I Googled the codes (p1131 / p1151). Obviously Fords are prone to these codes which could anything from the O2 sensor to the intake gasket. EGR to PCV. I dont know.

                              I am hitting about 145 myself. This has honestly been the best running car i have owned. That is saying a lot because I have abused this poor car more than any other as well.
                              All postings by BadOrderKing are public information, works of fiction, sometimes resembling the rants of a madman and in no way should be construed to represent the positions, views, or thoughts of any particular railroad carrier. No one listens to him anyway.

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