94pt40 taillight relay upgrade

[Gregory OConnor]

The tail lights on my 94 pt40 were so dim motorist would stop me or
use 'single digit' sign language to protest my failure to warn of a
stop or turn. When I checked the lights at each function, all was OK
but not par. I later learned that using both turn and brakes would
reduce the light to a warm glow. The 94 uses a Volvo taillight
assembly and the wire loom and pigtails that plug into the assembly
are Bluebird. The assembly uses a galvanized steel circuit board in
place of wires. the board connect to the loom with tiny galvanized
tabs that got weathered and reduced to pins. The Volvo car that uses
this taillight stores the assembly guts in its trunk whereas the bus
exposes the assembly to the engine compartment. The 8 pins for the 4
units are individually plugged in. All wires in the loom had a black
tarnish between strands further causing resistance and amp loss.

I contacted a forum member - Curt S for help with the dim situation.
He directed me to drive the bus to his house on a Saturday morning
and quickly; reviewed the problem; repaired some crossed 8 pin
connections; and designed a new relay fuse panel. With a new loom and
taillight assemblies the relays are not necessary. But I didn't want
to replace the wires all the way to the cockpit and the relays will
help power my trailers.

http://tinyurl.com/kguv3

or look in photos "miscellaneous "


Curt designed the relay panel to mount behind the fuel filter but I
dropped it below the false floor in the bedroom closet. I worked in
the closet, bent over until I got a brokeback from all the splicing
and screwing. The closet location will further protect the wire
connections and relays from weather. All splices in the taillight
loom are soldered and shrink tube wrapped. I globbed a semi solid
rubber compound around the 8 pin connection at the light assemblies.
Wires will have to be cut if the assembly is to be replaced because I
did not want to complicate the install for a repair that wont happen
if the connections are permanently sealed from weather.

How these relays work. The relays are remote switches that take the
juice from the batteries in the back of the bus and power the lights
also in the back. As it was, power went 40 feet from the batteries
to the cockpit then 40 feet back to the taillights. That 80 plus
feet of wire has resistance and you lose amps which are required to
make the lights bright. Now the turn signal lever in the cockpit
sends a signal to the relay-switch in the rear closet (low amp
required for this function), that relay-switch takes power from the
batteries in the back and sends the power direct to the tail light
with just 8 feet of wire (less resistance = more available amps).


Thank you Curt for showing me the light

Gregory O'Connor
94pt40
Romoland California