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Old March 5th, 2006, 09:40   #1
oilbug
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Default Car runs fine but won't turn over

Help! My 2000 Jetta decided not to start anymore (of course, on a rainy day an hour from home!) When I push start it, it runs fine, so it's probably something in the starter circuits (and not the immobilizer?). I can start it with the starter if I run a jumper directly to the small (low amperage) lead on the starter solenoid. I tried jumpering the relay 53 under the dash with no success. when I turn the key, I get good voltage everywhere I should (including right at the starter solenoid) until I put the solenoid back into the system, at which time I get no voltage when turning the key. Any ideas out there?
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Old March 5th, 2006, 10:34   #2
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Starter sounds bad. Also at that age the starter failing would not be out of the question. Replace it.
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Old March 5th, 2006, 11:36   #3
otbBlaine
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Quote:
Originally Posted by oilbug
I put the solenoid back into the system, at which time I get no voltage when turning the key
I think you found your problem. Same thing happend on my landcruiser.
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Old March 5th, 2006, 17:00   #4
Dick_Larimore
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Default Ignition Switch

If you can jumper directly to terminal 50 (solenoid coils) and the solenoid works, it is not likely to be a starter problem. Measure the voltage at the terminal of the solenoid while the solenoid is connected while someone turns the ignition key. If the voltage is much lower than when using a jumper wire, there is a high resistance in the vehicle circuit. The likely problem is the not so reliable ignition switch.
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Old March 5th, 2006, 17:03   #5
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Quote:
Originally Posted by Dick_Larimore
If you can jumper directly to terminal 50 (solenoid coils) and the solenoid works, it is not likely to be a starter problem. Measure the voltage at the terminal of the solenoid while the solenoid is connected while someone turns the ignition key. If the voltage is much lower than when using a jumper wire, there is a high resistance in the vehicle circuit. The likely problem is the not so reliable ignition switch.
^^^^^^^^^^What he said... beat me to it...
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Old March 5th, 2006, 19:22   #6
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Quote:
Originally Posted by Dick_Larimore
If you can jumper directly to terminal 50 (solenoid coils) and the solenoid works, it is not likely to be a starter problem. Measure the voltage at the terminal of the solenoid while the solenoid is connected while someone turns the ignition key. If the voltage is much lower than when using a jumper wire, there is a high resistance in the vehicle circuit. The likely problem is the not so reliable ignition switch.

Is the solenoid clicking at all when the wire is on the starter? How did you jumper the relay? Did you power the solenoid in the relay and nothing happened at the starter?
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Old March 5th, 2006, 20:15   #7
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Thank you all for the helpful hints. After much poking around behind the dash (and taking the interior of the car apart!) I've found that Dick Larimore and TDIJetta99 are the lucky winners. It seems the ignition switch applies enough voltage to confuse me, but breaks down as soon as the solenoid demands any current. Thus I was getting 12 volts at the wire to terminal 50 when it was disconnected, but no votage when connected. Checked the resistance across the ignition switch.... 60 kOhms. So now the question is, how does one change out the ignition switch... I'll search for a thread in here, anyone know where to find this info (or an ignition switch for cheap?)
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Old March 6th, 2006, 12:49   #8
brandtmeister
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wow, oilbug,
i had just the same happen last weekend (you should find my trhead a bit further down).

we had the same thing with the voltages being there when starter or relay 53 unplugged...

i got fixed by the dealer as i didn't have the time to order a switch and do it myself.

ignition switch was ~$90-100 and labor 150...for the grand prize of something like 260 bucks or so. (including tax etc). sucked, but currently couldn't afford to be without car... at least the dealer got it done in a few hours.
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Old March 6th, 2006, 22:22   #9
oilbug
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Thanks Brandtmeister.... I looked at the schematic for the car and they must pay their engineers to find ways to replace parts. They've got a relay to activate the starter relay (30 Amps inrush!) and ran all the current through the ignition switch. Most designs I've seen don't bother with a relay unless they're going to avoid putting large amperages through the ignition switch.... go figure.... thanks for the help.
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Old March 7th, 2006, 13:34   #10
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my thoughts exactly....
we ran all around town sunday night trying to get a relay 53...(it's just 8 bucks at the dealer....but event the dealer didn't have it in stock). from what I gather they are pretty aware that the ignition switch is marginal...and they had em in stock. so when they see the battery is good, they can kick the starter in (not sure how they do the "remote" start, bu i guess thye clamp 12 V to the starter), the first thing they double check is the ignition switch....

still not sure what the funny dotted line to the starter is( dotted line (i think coming form one of the battery high amp fuses) to a T connecter just before B/50...)
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Old March 7th, 2006, 21:10   #11
Dick_Larimore
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Default Oilbug

You hit in on the nose. It is strange (marginally stupid) that VW chose to run the starter solenoid current thru the ignition switch. It is difficult to design an ignition switch to handle the starting motor solenoid current. Most cars use a relay to carry the solenoid current and avoid the path thru the ignition switch. Besides, it's a lot easier to replace a relay than the ignition switch. One of the things that is especially hard on the ignition switch is to break (open) the solenoid current flow when the starting motor does not crank. This can happen when the ignition key flips out of your hand before the starter begins to crank, or the battery state-of-charge is low and the solenoid chatters and the starter never turns over. The current flow thru the ignition switch is high under these conditions and serves to pit and erode the switch contact surfaces.
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Old March 7th, 2006, 21:22   #12
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Quote:
Originally Posted by brandtmeister
still not sure what the funny dotted line to the starter is( dotted line (i think coming form one of the battery high amp fuses) to a T connecter just before B/50...)
Look to lower right of diagram. The text. see "---- Automatic transmission only"?
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Old March 7th, 2006, 21:30   #13
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Quote:
It seems the ignition switch applies enough voltage to confuse me, but breaks down as soon as the solenoid demands any current. Thus I was getting 12 volts at the wire to terminal 50 when it was disconnected, but no votage when connected.
Dick, correct me if I'm off base here, but wouldn't this show up with a voltage drop test on that wire? If the voltmeter reads battery voltage when the key is engaged, it would indicate a high resistance in that circuit, correct?

I remember learning this test years back, but I have never actually put it to use, so I'm foggy about it.
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Old March 7th, 2006, 21:35   #14
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V = IR

In this case, V = 12, I = small number, R= big number.
Should be I=big number, R=small number.

Insufficient CURRENT passing to the solenoid at the constant voltage.

I have no idea what "switch applies enough voltage..." means.
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Old March 7th, 2006, 21:57   #15
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Voltage drop is a better way to measure resistance. Worst case scenario would be a battery cable with just one strand left intact.

Turn VOM to Ohms and put the red lead on the + battery cable end and the black lead on the other end of the cable to the starter. You read zero Ohms resistance. Now, with the same connection, turn your VOM to Volts. It should read zero volts because there is no potential across the battery cable.

Now turn the key and that one strand is high resistance and now you will read almost battery voltage. You now have potential across that wire. The single strand is high reistance, but there is some voltage going across it, but the rest of what you are reading is the potential.

I'm explaining this poorly....

Let me try the WWW. This guy starts out by saying,

Quote:
I am an Electron Wrangler. While I'm not allowed to wear a cowboy outfit, my employer pays me to ensure that various electrons go exactly where intended and nowhere else.


so you can trust him.

You may suddenly find yourself consumed with the urge to hurt me. Your Jeep's starter barely turns, and I'm delving into the seemingly unimportant details of a voltmeter. Before proceeding (I'm talking about reading further, not hurting me) it is vitally important to understand that there is no pressure difference between the meter leads when they are connected, and thus 0.000 volts is displayed. That sounds pretty basic, but what does that have to do with anything?


If I haven't lost you yet, consider this next step. Instead of the meter leads connected directly to each other, what would happen if they were joined by a "Perfect" conductor? (There is no such thing as a "Perfect" conductor, but "Pretty Darn Good" is well within our grasp.) With the meter leads joined by a "Perfect" conductor, it is the same as if the leads were directly connected:





That piece of wire shown above happened to be completely isolated from anything else but the meter. Consider if that "Perfect" conductor was part of a circuit in motion. Even if bazillions of electrons were zipping past (Very high pressure or voltage) there would be no pressure differential between the meter leads. This is the very crux of this simple troubleshooting technique. This allows us to verify that any circuit element is allowing electrons through with no unwanted resistance. In this TooMuchFreeTimeVision(tm) image, the happy blue electrons are zipping past as part of a completed circuit. As with the piece of wire shown above, the meter is indicating 0.000 VDC:





Now let's place a restriction in the previously "Perfect" conductor. For the moment, consider it an unwanted restriction like a loose crimp or multiple broken strands. The restriction may not be as abrupt but is enough to cause a difference in pressure along the conductor. If too many electrons try to pass through, they will bunch up on the upstream side of the restriction. Remember this conductor is part of a circuit in motion, with the electrons traveling in a loop and performing useful work, such as powering a light. Even though we no longer have a "Perfect" conductor, we do have a theoretically eternal voltage source of stable output pushing the electrons. (Thanks, Craig!) Notice how the meter is not reading zero any more:






The voltage displayed is directly proportional to the amount of the restriction. Pretty cool, huh? With a simple meter hookup, a circuit under load can be easily tested for any unwanted restriction, or voltage drop. This is called a voltage drop test and is amazingly simple in use. It can be a bit difficult to grasp initially, so reread this section until it makes sense. Then sit on your hands, because you'll want to slap yourself once you realize how simple it is. The closer the voltage reading is to zero, the better the conductor is. Don't forget the all-important fact that this only works on a circuit in motion.

He explains it better than I do.
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