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From: Duncan Wood on 2 Jan 2010 10:16
On Sat, 02 Jan 2010 15:12:47 -0000, Duncan Wood <nntpnews(a)dmx512.co.uk>
wrote:

> On Sat, 02 Jan 2010 15:10:21 -0000, BigNose <bignose(a)stories.com> wrote:
>
>> I pulled down the rubber covers that allow wires to transfer protected
>> between the hatch and the car body. There are other wires in there
>> related to the rear wiper. I found the thicker black wires for the HRW
>> on both sides and pushed the prongs from my multimeter in until they
>> made contact and I could not find more than 6v - so having bypassed
>> the flexible bit - the problem is clearly somewhere else in the wires
>> path.....
>>
>> Is there a prime site where I should be looking?
>> The relay looks good and clicks and appears to function, could it be
>> the source of the lost 6v - or do you favour a waisted/cut/rusted part
>> of the wire run somewhere.
>>
>> Is there a way of determining if the left side or right side wire is
>> more likely to be suspect.
>>
>> Thank you so much for your help.
>
> One side should be grounded so that'll be at 0V, the other side should
> have 12V. If the wires are intact then check the actual switch on the
> dashboard.

Given it's a 306 then I doubt the switch has gone, I'm fairly certain
there's a relay just above the fuses , if I'm right then it's the orange
one.
From: BigNose on 2 Jan 2010 10:24
Yes Duncan, it is the Orange one. I think I will wait until my son
comes home (in his 306) so I can swop the relays and do a proper
comparison.

I cannot see a way of testing the relay when it's connected and the
terminals don't show any shorts. So I'm happy to wait a few days.

Thank you for your help.
From: Harry Bloomfield on 2 Jan 2010 12:17
BigNose wrote on 02/01/2010 :
> Is there a way of determining if the left side or right side wire is
> more likely to be suspect.

With the spades off the HRW and also switched off - connect your meter
set on the ohms range between a good ground and each spade in turn. One
spade should have a low value of resistance to ground, which should be
below one Ohm. That one is the ground connection - mark it as such. If
one reads a low resistance, but substantially more than one Ohm, then
you have a high resistance ground connection and have found the
problem.

Turn the switch on and the other spade should measure a little over 12v
when measured against a good ground connection, even if a low wattage
lamp is connected between it and the ground. The lamp should also
light. If it does not, or the voltage falls, there is a problem of an
high resistance connection on the 12v feed somewhere.

This could be a corroded copper wire, a connection which has burned, a
relay fuse or switch etc.. With someone watching the meter reading and
another going around the car checking sequentially all of the above
points, the voltage will most likely vary as the faulty item is wiggled
about.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk


From: Mrcheerful on 2 Jan 2010 12:37
BigNose wrote:
> Yes Duncan, it is the Orange one. I think I will wait until my son
> comes home (in his 306) so I can swop the relays and do a proper
> comparison.
>
> I cannot see a way of testing the relay when it's connected and the
> terminals don't show any shorts. So I'm happy to wait a few days.
>
> Thank you for your help.

it is easy enough to discover which of the relay connections goes to the
back window, then you can try putting a powered jump lead in that connection
and check for 12v at the rear window, if you still have only 6v then you
know the fault is in the wire between relay and the back end.


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