[VAC] Re: ail lights - update

["Weimers" <mweimer@xxxxxxxx>]

I just made my own "isolator" over the weekend.    I found four  12 volt ,
40 amp  relays for 99 cents a piece from MCM Electronics.  In my '71 GT
there is a "7 way connector inspection plate" on the front wall "behind" my
front sofa bed. This space is behind my pull-out drawers and it's quite
spacious. it's about 12 inches high, 8 inches deep and the full width of the
trailer. In other words, there was plenty of space to put my isolator.
Removing the inspection plate revealed all the wires from the main
connector, all sliced together with wire nuts. All I had to do was remove
the wire nuts and put my relays in the circuit. The main positive lead (10
gauge) from the car (and the trailer battery) provides the power. I put a 30
amp circuit breaker in the line for protection. The wires from the car for
the running lights, the two stop / turn signal lights and the reverse lamps
are attached to the coils of the four relays I used.  The relays are
attached to the front wall, out of sight behind the front sofa bed.

I tried it out today.  My lights appear to work better than I've ever seen
them work. When my flashers were on, my running lights did not get dimmer
when the "flasher" bulbs were "on". My reverse lamps were brighter than ever
...like maybe they would actually be useful!

My car's battery was not charged up well. I had the lights on for a while
and the voltage in the car started to drop towards 10 volts. Due to the
isolator, trailer lights still were bright!

My concern was that if I use the trailer battery to light up my lights, my
trailer battery might wind up being dead when I get to the campground. To
investigate this theory, I measured the voltage at the trailer battery when
the running lights were on and the motor in the car was running. I measured
13.7 volts at the trailer battery, so obviously charging voltage is reaching
the trailer battery from my car's alternator. No problem!

Next, I disconnected my trailer battery to see what would happen.  The
lights got a little dimmer, but they still worked fine. After some time,
when the car's voltage (without the engine running) dropped to 10 volts, and
all the lights were on, car and trailer (reverse lamps too), my trailer's
right stop light stopped working because the relay didn't get enough voltage
to pull the coil in and trip the relay.  The lights on the car were looking
pretty dim at that point too.  This situation would probably never happen,
so I don't think there will be any problems with this system.

Other potential problems? The wiring to my 7 way connector on the car is not
isolated.  If I get some kind of wiring problem in my car , the car's fuses
will still blow. This is hopefully, not likely.   The "Hoppy" isolator
attaches to the car up in the engine compartment. This would protect the car
from any trailer. This would be good. I put my isolator  in the trailer,
because I saw a big,  dry, protected spot that was really easy to wire into.
It was the easy way out!

The relays cost $4 and the connector I used cost about $3. The circuit
breaker was about $3.50 I used 4 new wire nuts too. So the total cost of the
isolator was around $12.    Now, if it keeps working, I'll have something to
be happy about !

After I put in my relays I decided  I could put switches in and make the
trailer lights light up even if the car was not connected.      I did  just
that.      I put in a rotary switch I had laying around. I can now test the
relay system and the trailer lights before the car is connected. I can turn
the reverse lamps on from inside the trailer while the trailer is in a
campsite and see behind the trailer at night (like using the "scare light"
on the side of the trailer).

MARC WEIMER
Punxsutawney, PA  -  Home of the Groundhog
#15767
1963 Globe Trotter
1971 Globe Trotter
http://users.penn.com/~mweimer/weimer.html