02 Outback trailer wiring?

[Jack Countryman]

I've pulled a small trailer a few times recently with my 02 Outback. While
the trailer lighting pigtail on the car tests normal without the trailer
hooked up, and shows current at the appropriate times for each of the three
connectors, the lights on the trailer never come on when its connected to
the trailer. I tried two other vehicles with the trailer, and with both of
them the trailer lights all work fine. So, I'm puzzled as to why I don't
get lights on the trailer hooked to the outback.

On one web site I saw a wiring pigtail for the Subarus advertised that
claimed to have separate wires to go to direct a power source sin addition
to the vehicle light circuits, with an explanation that the vehicle light
circuits did not have enough power (presumably amperage?) to operate trailer
lights without a separate power source.

Has anyone else had similar experience? If so, what light setups work? Is
there a way to rig this separate power source for the trailer connector
yourself? If so, from where, and how? Thanks.

 

[Victor Roberts]

I've pulled a small trailer a few times recently with my 02 Outback. While
the trailer lighting pigtail on the car tests normal without the trailer
hooked up, and shows current at the appropriate times for each of the three
connectors, the lights on the trailer never come on when its connected to
the trailer. I tried two other vehicles with the trailer, and with both of
them the trailer lights all work fine. So, I'm puzzled as to why I don't
get lights on the trailer hooked to the outback.

On one web site I saw a wiring pigtail for the Subarus advertised that
claimed to have separate wires to go to direct a power source sin addition
to the vehicle light circuits, with an explanation that the vehicle light
circuits did not have enough power (presumably amperage?) to operate trailer
lights without a separate power source.

Has anyone else had similar experience? If so, what light setups work? Is
there a way to rig this separate power source for the trailer connector
yourself? If so, from where, and how? Thanks.

I assume you have a 6-pin to 4-pin adapter between your OBW
and trailer. I have used a trailer with my 97 OBW for many
years and never had to use the power lead in the OBW plug.

 

[Jack Countryman]

The adapter plugs into the car wiring harness down in the spare tire well,
and is fed out the bottom of that space, ending in a flat 4 pin connector
(three leads for the lights, one for ground). I don't recall how many pins
were on the connector that plugs into the vehicle off hand.
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[Victor Roberts]

The adapter plugs into the car wiring harness down in the spare tire well,
and is fed out the bottom of that space, ending in a flat 4 pin connector
(three leads for the lights, one for ground). I don't recall how many pins
were on the connector that plugs into the vehicle off hand.
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There is a 6-pin socket attached to the car, so if you have
a 4-pin socket going to your trailer then you have seem to
have the proper adapter somewhere. You should see a rubber
covered object larger than the rest of the wiring somewhere
in the trailer wiring harness between the 6-pin plug and the
4-pin socket.

Back to your original question. If the trailer wiring from
your OB works on two trailers but not on one, and if none of
the lights on that one trailer work, then I suspect that the
ground wire may be broken on the trailer with the
non-working lights.

 

[Victor Roberts]

There is a 6-pin socket attached to the car, so if you have
a 4-pin socket going to your trailer then you have seem to
have the proper adapter somewhere. You should see a rubber
covered object larger than the rest of the wiring somewhere
in the trailer wiring harness between the 6-pin plug and the
4-pin socket.

Back to your original question. If the trailer wiring from
your OB works on two trailers but not on one, and if none of
the lights on that one trailer work, then I suspect that the
ground wire may be broken on the trailer with the
non-working lights.

Sorry, I now see that you said two other VEHICLES work with
that trailer, not that two other TRAILERS work with your OB.

When you say that the trailer lighting connector shows
current at the proper time, have you checked to make sure
that the pattern is the same as with the other vehicles? How
are you testing the connector - with a voltmeter (which
measures voltage not current) or a test lamp? Is the second
lead from the lamp or voltmeter connected to the ground pin
on the OB trailer connector or to the chassis of your OB? If
the latter you should test again using the ground pin on the
OB trailer connector instead of the chassis. Was the
trailer actually hitched to any of the cars used for these
tests? If so, the ground connection might have been made
through the hitch on some cars and not on others. This
would indicate a bad ground lead on the trailer or in the
wiring. Were the other cars domestic models that do not need
an adapter or were they imports that also use an adapter.
(Cars that share turn signals with stop lights do not use an
adapter. Cars that have separate turn rear turn signals and
stop lights need an adapter to combine these two signals to
drive the combined stop light/turn signal light on the
trailer.) Finally, can you find the converter in the lead
running from the OB connector to the trailer connector?

 

[S]

Hi Jack!

I've pulled a small trailer a few times recently with my 02 Outback. While
the trailer lighting pigtail on the car tests normal without the trailer
hooked up, and shows current at the appropriate times for each of the three
connectors, the lights on the trailer never come on when its connected to
the trailer.

Measuring the _voltage_ (I'm assuming that is what you are doing . .
..) is not the same as actually powering a light bulb; your voltmeter
draws very little current compared to a lamp, and this can sometimes
cause misleading readings. (I frequently have to demonstrate this to
disbelieving students ;-) Try again using a homemade "test light"
consisting of a couple wires connected to an automotive lamp.

On one web site I saw a wiring pigtail for the Subarus advertised that
claimed to have separate wires to go to direct a power source sin addition
to the vehicle light circuits, with an explanation that the vehicle light
circuits did not have enough power (presumably amperage?) to operate trailer
lights without a separate power source.

To the best of my knowledge, this is true; certainly the OEM adaptor
gets 12V from that 6 pin harness connector. As Vic suggests in an
earlier post, you may have a bad ground, or the adaptor may have
failed. Whatever, the "test light" described above will tell the tale.

If your adaptor will illuminate the test light while being connected
between the 4 pin connector's ground pin and all three of the active
pins, it will also power your trailer lights, assuming your trailer
wiring is good. If it will light the test light while connected
between the car's chassis and the active pins, look for a bad ground
(the adaptor grounds to a screw somewhere IIRC, or the ground wire to
the 4 pin connector may have been damaged). If you can't get the
adaptor to light the test light at all, try another adaptor.

FWIW, I have had similar "strange" problems with trailer lighting that
were finally solved by running an actual ground wire between the
trailer connector and the lights (as opposed to using the trailer
chassis as a ground).

Hope this helps a bit.

ByeBye! S.

Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101

 

[Victor Roberts]

To the best of my knowledge, this is true; certainly the OEM adaptor
gets 12V from that 6 pin harness connector. As Vic suggests in an
earlier post, you may have a bad ground, or the adaptor may have
failed. Whatever, the "test light" described above will tell the tale.

The non-Subaru adapter I use on my '97 OBW does not connect
to the 12-volt power lead in the 6-pin connector. But,
depending how the switching circuitry is designed some
adapters may use that pin. Designing the adapter to use the
12-volt lead would resolve the old problem of the flashing
frequency changing when the additional lamp load is added.
(That was solved in my OBW by using a heavy duty flasher
instead of the standard one.)

If your adaptor will illuminate the test light while being connected
between the 4 pin connector's ground pin and all three of the active
pins, it will also power your trailer lights, assuming your trailer
wiring is good. If it will light the test light while connected
between the car's chassis and the active pins, look for a bad ground
(the adaptor grounds to a screw somewhere IIRC, or the ground wire to
the 4 pin connector may have been damaged).

The 6-pin connector in my 97 OBW had a ground lead. It is
the lower right pin when looking at the end of the socket
with the locking widget on the top.

If you can't get the
adaptor to light the test light at all, try another adaptor.

FWIW, I have had similar "strange" problems with trailer lighting that
were finally solved by running an actual ground wire between the
trailer connector and the lights (as opposed to using the trailer
chassis as a ground).

I agree. You often cannot rely on the trailer chassis to
provide a good ground for the trailer lights unless all the
joints are welded. On tilt trailers and others with movable
joints or trailers that are delivered in parts and are
bolted together by the consumer the lights often require a
dedicated ground wire.

 

[Jack Countryman]

Since I was getting power on all three pins of the connector to both the
ground wire and the vehicle ground (as per both volt meter and a test
light), it seemed that things were working right at that point. Extra ground
wires/connectors didn't seem to matter, neither did whether the trailer was
hitched to allow a ground via the hitch. When I tried a different trailer,
everything seemed to work right. So, I crawled under the trailer I'd been
using, looking for problems there. The wiring harness splits into two wires
for each rear light, which were joined to the short wires coming from the
lights by crimp connectors. Somehow, it seemed all was good to those
connectors, then bad beyond that. So, I cut out the crimp connectors, and
soldered each of the wires, then taped them. For now, all is working. So
it would seem that those were not solid connectors.

Since the trailer worked OK with other vehicles, but not with the Outback,
it would seem that the possibility of the Outback putting less voltage or
amperage to the trailer may still be possible...but it is apparently enough
for now. Wait and see how long it all works.

Thanks for the ideas.
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