Maintenance Tips for the Mature Motorcoach Part 3

.......and now the conclusion of one of my favorite articles authored by Country Coach electrical engineer (and former service manager) Brian Keys

ELECTRICAL - Maintenance Tips for the Mature CC Motorcoach - Part 3 of 3 by Brian Keys,  electrical engineer at former Country Coach, LLC motorcoach manufacturer

Well folks, this is the last in a series of maintenance articles for the older Country Coach that began in the spring issue with a look at filter maintenance, and continued in the summer issue with a close look at the DynoMax chassis. This article will focus on the electrical gremlins that might take residence in your coach as the years pass by, and the steps you should take to eradicate them.

Before we continue, let us discuss a few notes of caution that you should be aware of when working on both low and high voltage electrical systems.  They are as follows:

* Low voltage electricity such as 12-volt or 24-volt does not present a risk of electrical shock. Battery and starter cables, however, carry a lot of current which can cause severe burns should a short circuit occur. Always remove the negative battery cable first and never allow the tool you are using to remove the positive cable to contact the chassis.

* Batteries give off explosive gasses. You should not work in close proximity to the batteries if they are gassing for any reason. If it does become necessary, you can cover the top of the battery completely with a water-soaked towel to absorb the gasses being produced.

* High voltage such as 120-volts or 240-volts can kill. Make absolutely sure that the circuit is not hot before you work on it. Don't assume that the circuit is dead because you have turned the switch off; use a test meter or similar to verify that the circuit is not powered.

* Think twice before working on 240-volt systems such as the transfer switch or shore cord. A simple wiring error in this system can result in an 'open neutral' that will typically destroy much of the high voltage electrical quipment in your coach such as the inverter, microwave, entertainment systems, etcetera. For this reason, and to avoid shock hazard, never use a “lollipop stick” or similar device to hold down the contacts of a failed transfer switch. It is a popular band-aid solution, but one that carries a lot of risk to both you and your coach.

With that out of the way, let's continue!

High Voltage Systems!

1. Transfer Switch.

Does your transfer switch shake, rattle and roll? Hopefully not, but it might develop a hum or chatter that would indicate dust or other contamination is preventing the relays from closing fully. With the switch un-powered, try blowing out any dust with high pressure compressed air. If you have an older transfer switch that has a small diode and capacitor between the relays, the ideal solution is to replace the switch. Those of you who are familiar with soldering can source a new diode and capacitor from Radio Shack, but the relays will often have reached their service life in this transfer switch and will (according to Murphy's Law) fail at the most inconvenient time. Does your coach mysteriously drop just one 'leg' of power after about thirty minutes of running on generator power? Does this leg of power cycle off and on? If this is true, then the likely culprit is a broken coil winding in one of the transfer switch relays. The two ends of the break will make contact when the coil is cold, but will separate again as the coil heats up due to thermal expansion. This is a common symptom with old transfer switches and for this reason, I again recommend that an old transfer switch should be replaced, not repaired.

2. Voltage Monitor or 'GFI' Circuit Board.

Do you regularly hear computer voices warning you that your shore cord polarity is reversed? If so, then you are probably very familiar with the location of the mute switch for the voice monitor system. To cure the actual problem will require replacement of the GFI Circuit Board. This board will probably have been damaged by a voltage spike on shore power and is typically located in the overhead dash above the passenger seat, or in the 'AC Feeder Panel' above the transfer switch.

Charging System

1. Battery Isolator.

This item is located in the engine compartment and was used on coaches with a Gillig chassis to allow the alternator to charge both chassis and domestic batteries while keeping them electrically isolated from each other. If you have a Gillig coach and your alternator is only charging one set of batteries, then the battery isolator has most likely failed. Failed isolators will usually have some cracking around one or more of the battery cable studs. The battery isolator is located in the engine compartment on the passenger side.

2. Charge/Boost Relay.

DynoMax coaches are equipped with a charge/boost relay in place of the aforementioned battery isolator. This relay connects the chassis and domestic batteries together when the engine is running so they both receive a charge. It also connects the two battery banks together when the 'battery boost' switch is operated to start your engine when the chassis batteries are low. If the alternator is only charging the chassis batteries and not the domestic batteries, then this component has likely failed and needs to be replaced.

3. Echo Charger.

This neat device provides a trickle charge to your chassis batteries from the domestic batteries when the latter is at 13-volts or higher, and it serves to keep your chassis battery charged when your coach is connected to shore power. If you experience problems keeping your chassis batteries charged then check the in-line fuses on the echo charger's wiring harness. These fuses typically fail when the chassis battery positive cable comes into contact with the frame during chassis battery replacement.

4. Battery Cables.

If you have a persistent charging problem that has so far defied all attempts at resolution, then take a close look at the battery cables. In particular, check to ensure the connections are clean and tight at the batteries, starter motor, alternator, and engine-to-frame ground cable.

5. Inverter Charging

Did your Heart Freedom 25, or Freedom 20 stop charging the domestic batteries for no apparent reason? If installed, does your Link 2000 show that the domestic batteries are receiving a bulk charge when they are in fact discharging? If so, then the first thing to check is the 300-amp, or 250-amp fuse on the inverter's positive battery cable. A voltage check across this fuse that measures anything other than 0-volts would indicate that this fuse has failed. If the fuse checks out good, then try hitting the upper right corner of the inverter's front panel with a closed fist (not a hammer!) once or twice. If this restores the inverter to normal operation then the inverter should be serviced when convenient to clean an internal board connection.

Instrumentation

1. Gauge Accuracy.

The accuracy of most analog gauges is limited, but if they are significantly misreading - especially when the dash gauge illumination is at full brightness - then you may have some undesirable resistance at the ground connections behind the dash. The easiest fix is to run an additional 12 AWG ground wire from the chassis framework beneath the dash to one of the daisychained ground terminals on the rear of the gauges. Does your coach have the digital gauge package or a digital dash where some of the gauges are not working? This dash instrumentation receives its information from two different sources via two separate twisted-pair 'network' cables. No readings on the tachometer, odometer, oil pressure and boost pressure gauges would indicate a communications failure with the ECM or Engine Computer Module. No readings on the remaining gauges such as speed, fuel level, and brake circuit pressure would indicate a communication problem with the 'DCU' or Data Collection Unit which is located in the steering compartment. In both cases, check the electrical connectors in the steering compartment for loose or corroded connections.

2. Ignition Solenoid.

Should your coach develop intermittent problems where nothing happens when you turn on the ignition switch, the most likely culprit is the ignition solenoid. This is located behind the access panel in front of the passenger seat on earlier Allures and Intrigues, and on the Front Run Board in the steering compartment on earlier Magnas and Affinities. Tapping on the relay with the ignition turned on will usually get you home, but be aware that you may have to tap it a second time when the ignition is turned off for it to disengage.

Domestic Electrical Systems

1. Alarm Systems.

Problems with alarm systems are not uncommon as they age, but how does one determine whether it is the alarm that has malfunctioned, or the much abused key fob? The trick here is to follow the manufacturer's instructions to set the alarm system into transmitter programming mode. If you hear the correct squeaks, squawks and chirps as described in the instructions, it is safe to assume that the alarm system is operational but your key fob transmitters are not. If the alarm system groans or gargles unexpectedly and it has good voltage at its power connection, then it should be replaced. It is usually more cost effective to replace an old alarm system with a new one after about thirty minutes of troubleshooting as opposed to spending three or four hours of diagnostic time trying to coax life into one that has long expired.

2. Poor Antenna Reception.

If your TV picture is somewhat 'snowy' while others near you have great reception, then it is time to check for loose coaxial cable connections behind the TV itself, and also on the rear of the TV-Boost, and A/V switcher control. If this does not improve the reception, then the next item to check is the coaxial cable connections to the antenna itself. You might also consider cutting the cable back a little to install fresh connectors in place of those that may have corroded.

3. Entry Step.

Do your entry steps go out when you close the door, go in when you open it, or exhibit other erratic behavior? If the steps are receiving good voltage, and the ground is clean and secure, then the first item to check is the door switch. If the steps seem to work properly as you cycle this switch in and out with your finger, then it probably needs to be adjusted. If not, then the switch should be tested with an ohm-meter for good continuity and replaced if necessary. In some cases, the entry step's 'brain' may be a little confused. But, I have some good news! Brain transplants are readily available and are easy to replace. If you replace an older 'white brain' with the newer 'black brain', you will also need to add a relay to change the logic of the entry door switch or, better still, replace the entry door switch also. The latter is generally not an easy task so be prepared for battle!

This is not by any means a complete collection of electrical gremlins, but hopefully the solutions presented here will shed some light on a mystery or two that may have plagued you for some time.