Re: Earth resistance

PCPaul wrote:
On Fri, 25 Jan 2008 13:10:29 +0000, Doki wrote:

"Doki" <mrdoki@xxxxxxxxx> wrote in message
news:5vu50cF1njaj9U1@xxxxxxxxxxxxxxxxxxxxx

"Dave Plowman (News)" <dave@xxxxxxxxxxxxxxx> wrote in message
news:4f664e3564dave@xxxxxxxxxxxxxxxxxx
In article <5vrtndF1nuj0jU1@xxxxxxxxxxxxxxxxxx>,
Doki <mrdoki@xxxxxxxxx> wrote:
I'm trying to track down a fault with my car's clocks. One earth
is showing very low resistance (negative for some reason on my
cheapy multimeter), and the other is showing around 50 ohms. Does
this sound anything like right?

If the meter zeros ok on the ohms scale sounds like there's some
volts there.

50 ohms is far too high - I doubt it ever was a true earth
connection. What colours on the wire?

Grey.

By the way, the clocks started playing up after a battery charger was
connected up in reverse. Several sets of clocks have exhibited the
same faults, so I reckon it's the wiring. Am I right in thinking
that the diode between pins 3 and 13 would have allowed basically an
open circuit so it's likely the wiring's knackered somewhere? Or
should it have munched a fuse?

That's just *slightly* relevant information...

There's all sorts of things on there could have blown with reverse
polarity, even if a fuse did go to protect them eventually. The
voltage regulator is one - check between ground and the output pin
when the battery is connected - it's probably a 12V regulator so you
should be getting a steady 12V if the battery is giving it the normal
13.5V+.

Right. Here's a load of background info:

Battery charged backwards, clocks stop working.

I assume some part of the clocks must be dead, so I rip apart the clocks.

I buy a second set of clocks. Still exhibits same faults.

I buy a third set of clocks. Again, same faults.

It's looking very much like it's not the clocks at this point, and so I'm
thinking it must be the wiring. It's as if the computer chip at the bottom
of the wiring diagram has no idea that the ignition is on or the car is
started - no flash of the oil warning light before the key is turned etc.
Pin 11 is the constant live to keep the time on the clock and memory for the
MFA, and leads to fuse 21, which is the one that usually fixes the MFA
computer if it's playing up. Pulling and reconnecting fuse 21 doesn't fix it
now... Pin 13 is switched with the ignition, but I can't see how it can't be
getting through to the MFA chip on two different sets of clocks.

Here's a complete pin out of the clocks taken from the GTI Club:

1 Outside Temperature
2 Coolant low level sensor
3 Ground
4 Stalk Switch pin 4
5 Stalk Switch Pin 1 / Ground
6 Stalk Switch Pin 3
7 Cruise Control / CIS
8 High Oil pressure switch
9 Low Oil Pressure switch
10 Rev Counter
11 Digital Clock power
12 Dash and Digital Clock lighting
13 Power
14 Not used
15 Stalk Switch Pin 2
16 Alternator Warning Light
17 Oil temperature Sensor
18 Not used
19 Outside Temperature
20 Not used
21 Fuel Gauge
22 Not used
23 Coolant Temperature Gauge
24 Direction Indicator lamp
25 Main beam lamp

From my meddling, it seems like this pin out data is correct.

Voltage reg should be between 9.5 and 10.5V. It puts out something around
9.95V. The only other faults I can think of off the top of my head is the
unusal readings on Pin 5, which I've not had chance to check over yet.

.

Relevant Pages

  • Re: Earth resistance
    ... Battery charged backwards, clocks stop working. ... turned etc. Pin 11 is the constant live to keep the time on the clock ... Stalk Switch Pin 1 / Ground ... 17 Oil temperature Sensor ...
    (uk.rec.cars.maintenance)
  • Re: Earth resistance
    ... If the meter zeros ok on the ohms scale sounds like there's some ... the clocks started playing up after a battery charger was ... turned etc. Pin 11 is the constant live to keep the time on the clock ... Stalk Switch Pin 1 / Ground ...
    (uk.rec.cars.maintenance)
  • Re: The real twin paradox.
    ... there is no paradox in the sense of contradiction. ... Since the paths taken by the twins in this experiment are symmetric, ... their clocks tell the same time. ... temperature to 40 degrees and you keep it at that temperature ...
    (sci.physics.relativity)
  • Re: The standard of time and identical clocks
    ... the temperature increase for each bucket? ... What if you have a two thermometers that differ in rate changes? ... so the heat is final factor. ... Explain how two identical clocks could have ...
    (sci.physics)
  • Re: The standard of time and identical clocks
    ... the temperature increase for each bucket? ... so the heat is final factor. ... Explain how two identical clocks could have ... The standard has a problem if the clocks are not agreeing ...
    (sci.physics)