February 1, 2006

TT #46 "Ground" Maintenance, Auxiliary Start, and Generator Start Tips

By: Rob Lowe

Technical Tips #46 


"Ground" Maintenance, Auxiliary Start, and Generator Start Tips

I have often read messages on the Bounder "Yahoo Group" about a vehicle or a generator intermittently failing to start. Usually the writer indicates that depressing the Auxiliary start switch failed to correct the situation and upon checking the voltage of the chassis battery, he discovered that the battery seems fully charged. Where does the writer look? Most initial responses instruct him to check the cable connections, clean them, check the starter solenoid and its connections and so on… However rarely does the writer get the response which is the most likely solution: Follow the (black) ground wire from the batteries to the frame connection, remove it, clean the contact point on the frame, and the cable connector and reinstall. Many early production Bounders have ground connections that were installed and left unprotected from the elements allowing corrosion. Even the dissimilar metals (copper connector and steel frame member) will set up a corrosive reaction over time. It is possible that the frame contact area was not cleaned of the paint put on the frame to inhibit corrosion. All of these situations will, if left unattended, result in a "no start" condition. The solution, which was addressed in the Fleetwood Maintenance Manual, is to conduct an annual inspection of all battery and ground connections, cleaning and protecting them as required. On newer Bounder models, the connections are covered in a red protective paint coating that greatly reduces the risk of corrosion. I highly recommend using Corrosion Block® on both the wire cable connection, the area of contact on the frame and the battery terminals. This will provide protection from corrosion at the molecular level and Corrosion Block® will migrate under the wire insulation, to provide a roadblock to further corrosion. You can, if you wish, use a protective paint made for this purpose after you have reinstalled the wire, however I do not see any reason to do this, after using Corrosion Block®.

Once you have tackled the first ground connection, do the same on the Coach (or House) battery ground and then check the generator ground connection. While you are inspecting them, look carefully at the red, positive battery connections, cleaning and protecting them as well. Then look carefully at the engine and you will find a ground strap from the engine to the frame. Remember that, on diesel coaches, there are both red and black connections at the front for control circuit and generator operation, as well as at the back, near the batteries and any corrosion in these connections can cause an intermittent start condition.

You will also find poor grounding to be the source of many erratic gauge readings. Any plug-in connector, which has tin metal connection pins, will corrode when in contact with copper printed circuit board contacts. Instrument panel warning lights and gauges have a copper circuit "board" (actually a thin plastic sheet) with copper connections terminating in a junction block. A plug in connector from the coach wiring harness provides the panel with the information required to give the display of information you depend on. I have solved many gauge problems by removing the connector, lightly cleaning the copper connections with an ink eraser, applying Corrosion Block® to the connector and reinstalling.

While on the topic of "no start" situations, it is important to understand what the auxiliary start button does and how to use it. The push button "Aux Start" button engages a relay that temporarily connects the Coach batteries to the Chassis batteries to allow the Coach batteries to "Boost" the Chassis battery allowing the engine to be started. You must depress the "Aux Start" button while turning the ignition switch for this Boost to occur. As soon as the "Aux Start" button is released, the batteries are once again isolated. This same relay is often controlled by the coach electronics to allow the engine driven alternator to charge, first the Chassis battery and then the Coach batteries when driving.

Many questions are posed to the Yahoo Group about which battery powers the generator. According to Fleetwood, the Coach (or house) batteries always power the generator. If the chassis battery was used, and it was dead, the auxiliary source of power (your generator) would not be available. When you have your shore power cord connected to a source of 120-volt electricity (such as in a campground) the coach batteries are recharged by the converter (on gas rigs) or the inverter/charger (on diesel rigs). Therefore, the Coach batteries should have sufficient power to start the generator. From about 1995, the converter also charges the chassis battery as well.

One last tip: If your engine driven alternator fails while you are driving; start your AC generator. It will provide sufficient power to keep all systems running and charge your batteries until you can get your alternator repaired.


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