Technical information

battery will be drained after just two or three hours of
towing — the wheels going round and round “wake
up” the computer, which turns on a number of elec-
tronic devices that drain the battery in short order. It is
for these select vehicles — which must be towed with
the battery disconnected — that we made the Auto-
matic Battery Disconnect. Always check the owner’s
manual to see what it says about towing.
Our trickle charger will not overpower this high rate
of discharge so you must still disconnect the battery.
• Ignition switch position — it’s very common for cus-
tomers to accidentally leave the ignition switch in the
wrong location. This will drain the battery in short or-
der. Again, the trickle charger will not compensate for
this.
• The motorhome park lights aren’t on. The charge
circuit is the motorhomes park lights. If the customer
doesn’t turn them on, the battery won’t be charged.
• The charge circuit may be loose, not connected or
there may be a poor ground between the vehicles.
Obviously this would prevent the charge circuit from
working. Even so, InvisiBrake has such a low electrical
draw you’d still get two or three days of towing before
the battery was completely discharged, if that was the
only drain.
Assuming there’s no other drain, you can tow in-
definitely with InvisiBrake and you’d never have to
stop to charge the battery. If the customer’s battery is
draining, there’s something else draining it.
Concern
It takes an hour and a half to install the motorhome
components and run the wiring to the rear of the mo-
torhome. That’s a lot of time, especially on top of the
car components.
Clarification
The biggest time-consumer is stringing a wire from
the front to the rear of the motorhome. Here are some
tips that can help in many installations:
• Many vehicles are pre wired for a supplemental
braking system. There are wires pre-strung from the
front to the rear already and one of them can be used
for our monitor wire. The following vehicles are pre
wired:
• Freightliners built after December of 2002 are
pre wired.
• Monaco year models 2006 and newer are pre
wired.
• Winnebego year models 2007 and newer are
pre wired.
• Most new motorhomes have a seven-way plug.
Check to see if the blue brake wire is connected at the
rear of the socket. This is the wire that would normally
be used to install an electronic brake control in the
dash of the motorhome (if the owner was towing a
boat or tow dolly). Verify with the owner that he won’t
be using a brake controller for a boat or dolly. If not,
use the blue wire for the monitor system — it’s already
running to the dash.
continued from preceding page
brake pedal arm and how much pressure is required
to brake properly.
The brake arm is a lever. The closer to the fulcrum
point, the harder you must pull to get the same brak-
ing. If you have the brake pedal clamp attached high
on the arm it may require twice the psi as you’d get by
attaching the clamp just above the brake pad. Always
try to locate the brake pedal clamp as low as it can go
on the arm so you can reduce the pressure.
If it’s already mounted low on the arm, there’s a
good chance you’re not getting enough vacuum.
Check the following:
a. Is there good vacuum coming out of the con-
troller? If not. the compressor may not be producing
vacuum properly and the factory will replace it.
b. Is there good vacuum at the tee under the hood?
If not, the vacuum line may be pinched (like in a seat
track from the seat being moved back). Or it may have
been cut, which would prevent most of the vacuum
from reaching the brake booster.
Remember it’s the vacuum that energizes the pow-
er brakes on the car. Without it you’d have to step on
the brakes very hard to get braking. One hundred psi
will give you lots of braking if you have good vacuum
and the clamp is attached low on the arm.
So long as all four mounting screws are used to se-
cure the pulley to the firewall, you should never have
an issue with it pulling loose (barring any older cars
with rusted-out firewalls). One hundred psi sounds
like a lot, but you can literally grab the end of the
cable and hold it, preventing any movement created
by 100 psi vacuum in the air cylinder — we know be-
cause we’ve done it. The pull is purposely not too hard
because the power brake system does the work for
you.
Concern
The charge line isn’t heavy enough — InvisiBrake is
draining the battery.
Clarification
The wire in question only trickle charges the bat-
tery. Charging the battery too fast can “boil” the bat-
tery, hence the two-amp trickle charge. So the wire is
plenty big for its purpose.
InvisiBrake only draws from the battery during
braking. The vast majority of the time you’re not brak-
ing and this is when the trickle charger keeps the bat-
tery topped off.
It’s likely that one of the following scenarios is caus-
ing battery drain:
• The fuses must be pulled on many cars in order
to tow them. If the fuses aren’t pulled there’s a con-
tinual drain of eight to 12 amps. Some installers see a
“charge line” and assume it will make up for whatever
draw the car has. This is not the case — you must still
pull the fuses according to the manufacturer’s recom-
mendations.
• In cars with sophisticated computer controls, the
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