Date: Sun, 9 Aug 1998 09:02:09 -0700
Reply-To: Lawrence Dongilli <buspilot@WORLDNET.ATT.NET>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Lawrence Dongilli <buspilot@WORLDNET.ATT.NET>
Subject: Re: Air Conditioning wiring burning (Urgent....Please Read Me!)
Content-Type: text/plain; charset=ISO-8859-1
----------
> From: EMZ <vw4x4@FYI.NET>
> To: Vanagon@VANAGON.COM
> Subject: Air Conditioning wiring burning
> Date: Sunday, August 09, 1998 12:16 AM
>
> The heavy gauge wiring that goes to the 50 amp fuse
> started to burn tonight as I was driving. The AC was
> on, and I have been having problems with this wiring,
> earlier this week. No fan on speed 3 only.... Kinda
> strange, I went back to the C-pillar and bumped a
> relay and the fan started to work. Tonight it seems
> to take a punch to get it to work, next thing
> I knew the smell of burning wires.......SO I turned
> it off. Checking things out showed the wiring to the
> 50 amp fuse and that area were hot.
>
> anyone have anything like this happen?
>
> Eric
.....YES, I just found this problem in our '86 Syncro....yesterday evening!
My theory is this......the crimped on connectors have developed some
internal resistance as they have aged and oxidized. These wires draw very
high current and _any_ amount of extra resistance in that crimp is going to
heat up to some degree as a result. The big clue to this is that the main
feed wire to the AC system was staying at ambient temperature along its
length...._only_ the crimped end of the wire was getting hot. If excessive
current was the problem, the _entire_ wire should be getting hot....and the
fuse would likely blow. When I was tinkering in that area looking at
_other_ things, I found the lugs going to both sides of that 50 amp fuse to
be so hot that spit would SIZZLE (yet everything in the AC system was
functioning properly and the crimps all looked proper)! I immediately shut
the system down and cleaned the contact surfaces, as there was a bit of
oxidation present. When I retried the system, I found no change. To test
my suspicion of a high resistance crimp, I cut off the old lug and replaced
it with a fresh one. The new lug was crimped _and_ soldered. The next
time I powered up the system, that lug stayed _cool_......ambient
temperature actually! The next lugs in the chain had the same problem (on
the other side of that 50 amp fuse). I replaced and soldered those
too.....with the same results.....they all stay cool....absolutely cool! I
am going to be tracing through the entire high current loop for the AC
system in that area as there are other connections that are getting hot
too.....including the connections that go into those relay sockets!
Note, when I checked the resistance of the wire through the lugs, the
higher resistance didn't really show up on my meter. When I say 'high'
resistance........I only mean 'more than zero' (effective)....a fraction of
an ohm! With all the current that these wires carry, any extra resistance
is going to turn those crimps into efficient heating elements......._it
doesn't take much_!
I sent a post days ago titled 'Check Your Grounds". I must update that to
"Check ALL Your Connections"......particularly the high current ones.
Please, for the sake of your wiring, check this soon. As a test, you don't
even need to have the engine running. After pulling the cover on the left
C-pillar, just turn the keyswitch on, and then turn on the AC system. You
will hear the relays click, the AC clutch engage, the radiator fan turn on
and the AC blowers will spin up at whatever speed setting they are sitting
at. Carefully touch as many of the crimped lugs back there as you can
(safety first - make sure you take off your rings/jewelry first.....unless
you want to turn your wedding band into a shorting bar!). Be prepared for
some hot lugs.......with this condition they can easily get hot enough to
burn you.
Happy Hunting
Lawrence Dongilli
| 
