October 1, 2001

TT #25 Bounder and Tow Car Electrical Problems

By: Rob Lowe

Technical Tips #25 


Bounder and Tow Car Electrical Problems

A reader wrote that his 1996 Bounder four way hazard flasher works for about five minutes then quits. The solution is replacing a blown fuse, which he has done five times. When this situation occurs he has no brake or signal lights on either the Bounder or the tow car. This nagging problem has forced him to refuse to use the hazard warning lights. He questions whether the problem is the flasher or what?

My experience with the four-way or hazard warning flashers on the Bounder is that the addition of a tow car to the Bounder adds too many lights for the power supply fuse to handle. If the flasher quits or overheats then the flasher is the problem and a Heavy Duty or Electronic Flasher is the solution. However given his experience there are two solutions. The reason the fuse blows after a period of time is that the current draw increases to the point that the fuse overheats and blows. On the Bounder, activating the hazard flasher results in flashing four to six front signal lights (including body side flashers) and four rear bulbs. On the tow car an additional two to six bulbs are flashing. The current draw is about 1.5 amps per bulb or 15 to 24 amps depending on the number of bulbs. Add some resistance in 50 feet of wire and this will often exceed the fuse rating. The reader's situation indicates that the current draw is "on-the-line".

The first area to check is the ground connection at the tow car. Usually the harness is relatively thin wire that is grounded at the rear of the car in the trunk area near the taillights. This adds an additional 20 feet of wire with resistance into the circuit. Check the ground connection where it is enters the tow car body. In the typical four wire harness, the wire colors are White: Ground, Green: Right Signal & Brake, Yellow: Left Signal & Brake and Brown: Taillights. If the ground connection on the Tow Car is not clean and shiny and firmly connected to a clean (no paint) portion on the car body then there will be higher resistance. I recommend connecting the ground to the Tow Car body at the front as soon as possible after it enters the tow car, as well as a good connection at the rear. The tow car body then provides a good ground. Thoroughly clean the tow car plug and the Bounder socket, since it is the metal shell that provides the ground. If your tow car has a jumper cable with dual plugs for connection to the Tow Car and the Motorhome, thoroughly clean both plugs. While checking the sockets make sure that all the pins are clean and shiny. With all power off, lightly scrape each pin using a small file or sandpaper to clean each one, and then coat with di-electric grease available at auto parts stores. (This grease is often used for lubricating ignition-wiring connections).

In addition to checking the wiring to the tow car, ensure that each lamp connection to the harness is solid. Many installations use wiring clips clamped over the car wiring. These can create problems because they do not make a good solid connection, but they work and they allow a quick installation. The best method is a proper soldered wire to wire joint.

These inspections and changes recommended should solve the fuse burnout problem. If the fuse that burns out is a 15-amp and you have determined that the current draw based on the number of bulbs being flashed is above that, then install the next larger fuse (20-amp). If it is a 20-amp then go to a 25-amp. Any serious short will still blow the fuse, providing adequate wiring protection, but there will be a little higher tolerance when towing. In no case should a fuse exceeding 25-amp be installed.

One additional benefit is that the tow car tail and signal lights will be brighter with a good ground. I experienced a similar fuse-blowing situation with the running and clearance lights when towing and lost all exterior lamps and the dash lights. I did the math and discovered that the addition of the tow car tail and license plate lights added too much draw to the motorhome (calculate about 3/4 to 1 amp per bulb). I replaced the 15-amp fuse with a 20-amp and continue to clean the ground connection, with no further problems. I can tell immediately when the ground connection (at the plug into the motorhome) needs to be cleaned when I hook up the tow car and test the taillights and the four way flashers together. The taillights become very dim, and almost die out when the higher current flashers operate. Cleaning the plug solves the problem.


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