ALTERNATOR  PROTECTION CABLE

Every GMC Motorhome should have the APC assembly.  Even the 1977/78 models do not protect the Nichrome Resistance Wire!

GMC published a Tech Note in 1974 to identify a problem that let the alternator light glow dimly on most GMC Motorhomes’. The reverse voltage glow did not cause any damage, but GMC did modify their production in 1977/78 models of the GMC Motorhome to eliminate the condition.  The “Fix” eliminated the reverse voltage problem for the alternator light but did not protect the Nichrome resistance wire that runs in a wire bundle from the fuse block behind the glove box, to behind the instrument panel. 

When a high reverse voltage occurs due to a battery isolator or alternator failure, the Nichrome wire can melt the insulation on wires in the wire bundle.  This event has even started fires behind the dashboard.

The Alternator Protection Cable protects against the damage that a high reverse voltage would do to the alternator light and the Nichrome wire.  The APC uses the GMC solution to the problem but also protects the Nichrome Resistance Wire.  Any GMC owner can install the APC.  The original two-conductor cable is unplugged from the alternator and plugged into the APC assembly.  The APC assembly is then plugged into the alternator. This completes the installation.

                                    

Other solutions to this problem require removing dashboard panels, cutting wires and permanently attaching components.  Most Owners do not want to do these irreversible modifications or spend the money to have them done. The APC can be easily removed if an owner wants to conduct a test without the APC.  For a more complete technical description of this topic go to the web page:
http://bdub.net/gmcmotorhome.info/engine.html#alternator

WHAT ARE THE SPECIFICATIONS FOR THE APC?
The components are rated at 6 Amps at 1000 peak reverse volts.
The assembly is mechanically and electrically tested before shipping

WHAT IS THE WARRANTY FOR THE APC?
The APC is free; there is no warranty, use at your own risk.

WILL THE APC REPAIR BURNED OR SHORTED WIRING?
This assembly will only block reverse voltages as stated in the Brochure.  It will not repair any existing or future faults in the electrical system.

HOW DO I TEST THE APC?
With the APC removed:
Turn on the ignition switch but do not start the engine, the alternator light should light brightly.
Start the engine, the alternator light should go out or go dim.
Turn off the engine

With the APC installed:
Turn on the ignition switch but do not start the engine, the alternator light should light.
Start the engine; the alternator light should go out.
Turn off the engine

My alternator still had the same behavior after installing the APC.  The alt light would glow dimly some of the time and be out the rest of the time.  It is as though the dim light is associated with fully charged batteries and the out light when the batteries are recharging again - just a guess.  Any idea what is going on????

This is a legit problem not the reverse voltage problem.  The battery voltage is higher than the alternator output....  This indicates an alternator problem and maybe even a slipping belt.  If you have the maintenance manual there is a trouble-shooting chart there that should help.  The APC assembly eliminates the reverse voltage Non-problem indication.


HOW DO I ORDER AN APC?