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901304 REV D 02/28/2017, PG 5 OF 23
Important Wiring Notice—Please Read
Some Vehicles May Have Had Some or All of Their Radio Interference Capacitors Removed.
There Should Be a Capacitor Found At Each of the Following Locations:
1. On the positive terminal of the ignition coil.
2. If there is a generator, on the armature terminal of the generator.
3. If there is a generator, on the battery terminal of the voltage regulator.
Most alternators have a capacitor installed internally to eliminate what is called “whining” as
the engine is revved. If whining is heard in the radio, or just to be extra cautious, a radio
interference capacitor can be added to the battery terminal of the alternator.
It is also important that the battery lead is in good shape and that the ground leads are not
compromised. There should be a heavy ground from the battery to the engine block, and
additional grounds to the body and chassis.
If these precautions are not observed, it is possible for voltage spikes to be present on the
battery leads. These spikes come from ignition systems, charging systems, and from
switching some of the vehicle’s other systems on and off. Modern computer-operated
equipment can be sensitive to voltage spikes on the power leads, which can cause unexpected
resets, strange behavior, and/or permanent damage.
Vintage Air strives to harden our products against these types of electrical noise, but there is
a point where a vehicle’s electrical system can be degraded so much that nothing can help.
Radio interference capacitors should be available at most auto and truck parts suppliers. They
typically are cylindrical in shape, a little over an inch long, a little over a half inch in diameter,
and they have a single lead coming from one end of the cylinder with a terminal on the end of
the wire, as well as a mounting clip which is screwed into a good ground on the vehicle. The
specific value of the capacitance is not too significant in comparison to ignition capacitors that
are matched with the coil to reduce pitting of the points.
Care must be taken, when installing the compressor lead, not to short it to ground.
The compressor lead must not be connected to a condenser fan or to any other
auxiliary device. Shorting to ground or connecting to a condenser fan or any other
auxiliary device may damage wiring, the compressor relay, and/or cause a
malfunction.
When installing ground leads on Gen IV systems, the blower control ground and ECU
ground must be connected directly to the negative battery post.
For proper system operation, the heater control valve must be connected to the
ECU.
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