Hi folks.
Now that I have my TR6 running again, I can focus on chasing this
short in the purple circuit. I have Dan Masters' book, but I need
some feedback on things in order to cement them in my
electrically-challenged brain.
I've drawn out separate schematics for each of the four systems wired
in purple; horn, courtesy lamps, glove box/trunk/seat belt, and
hazard. Now I am systematically picking through each diagram,
testing each run of wiring for resistance.
Please keep in mind that I am unable to check for voltage in these
circuits because even a 35 amp (American rating) fuse pops instantly
when the battery is connected. I could connect a jumper wire from
the battery to the 'trunk' of the purple wires and bypass the fuse,
but I expect that if I did that all the purple wires would burn up,
and I'd like to avoid that. If I'm wrong in that assumption, please
correct me.
I've started out with the horn circuit, and I think I've found a
problem, but apparently it's not the only one. Please tell me if I'm
making the correct conclusions based on my findings here.
(Understand that the horn push part of the circuit has been
disconnected and non-functional for quite some time)
On the purple wire leading from the fuse terminal to the horn relay I
get about 2 ohms, which means this run of wire is okay. Likewise, on
the short looped wire that goes from the previous wire to another
terminal on the horn relay I get 2 ohms, although the connections
appear dirty and it takes some wiggling of the probes to get the
needle to swing.
On the purple/yellow wire which leads to both horns: Here I touched
a probe to the relay-end of the purple/yellow wire, and the other
probe to ground, since the horns are always connected to ground.
Here I got about 8 ohms, which I think makes sense because I'm seeing
the added resistance of the horns themselves, and so I think that
branch of the circuit is okay.
On the purple/black wire which leads to the steering wheel and horn
push, I've got some weird things going on. I have disconnected the
bullet terminal which is between the horn push and the relay, and
first I tested continuity between that bullet terminal and the
relay-end of the wire. This was okay, at about 2 ohms. But when I
touch one probe to the relay-end of the purple/black wire and then
the other end to ground, I think I SHOULD get infinity ohms. This is
because the end of that purple/black wire is disconnected at the
bullet and is floating around in thin air, and therefore it has no
connection to ground. Right? But instead of infinity, I get a
reading of 20 ohms. This, I'm quite sure, is wrong.
So, I thought of a good way (I think) to see if that wire was the
source of my problem. I disconnected the purple/black wire from the
relay so that, in theory, that particular wire is totally isolated
from the purple circuit. Then I inserted another 35 amp fuse and
then touched the negative battery cable to the battery. I expected
that if that purple & black wire was the problem, that now the fuse
would NOT blow because now that wire (and whatever it may be
connected to) is totally isolated from the circuit. But, guess what?
The fuse popped instantly.
Now that may mean that I've got another problem elsewhere in the
purple circuit, and I can deal with that. But I just want to know if
my thought processes and conclusions are correct here thus far. I
hate electricity, but I'm trying hard to get a grip on it.
Certainly, Dan Masters' book has been a great help.
Also, I know (thanks to Dan's book) that I'm not supposed to be using
American rated 35-amp fuses. Of course, that's what I've BEEN using
for the last 13 years, but I will use the fuses that Dan recommends
from here on out. Meanwhile, I may as well burn up my supply of
spare 35-amp fuses!
And I may as well ask, is there anything that could be happening
UPSTREAM of that purple fuse that would cause this? I've come to the
conclusion that the problem HAS to be downstream of the fuse, because
when I measure resistance between the fuse-end of the purple wires
and ground (with no fuse installed) I get a little under 2 ohms of
resistance when apparently I should be seeing infinity.
Thanks all!
--
Pete Chadwell
1973 TR6
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