Practical troubleshooting your RV, 101 #1

[Leroy Eckert]

Thanks for the detail Ralph. While I understand this I will print this off and put it in my files as a memo for myself and for the next owner. Great stuff for BB folks. Merry Christmas. Leroy Eckert 1990 WB-40 Smoke N Mirrors Dahlonega, GA Royale Conversion --- On Wed, 12/24/08, Ralph L. Fullenwider wrote: From: Ralph L. Fullenwider Subject: [WanderlodgeForum] Practical troubleshooting your RV, 101 #1 To: WanderlodgeForum@yahoogroups.com Date: Wednesday, December 24, 2008, 3:50 PM Hello everyone; Electrical systems in any venue, to many, is confusing and it does not have to be. With just a few simple rules, one can do a systems check no matter if it is a 12vdc/24vdc or an 110vac system. The words, what? where?, how? and why? come to mind as the very basic start to finding a problem with systematic troubleshooting. What? equates to, What is the real problem? (does not mean what the problem appears to be.) Where? equates to the physical location of items along a "path" in a given system. How? equates to how does it or is supposed to work? Why? (remember when Dad used to say "there is no such word as why." The why equates to why did it happen in the first place. It is important to try to learn how a system is designed to work or the right way to say this is "know the sequence of operation." If you know how it is supposed to work then you are ready to start trying to; "recognize" "localize" and "isolate" a problem. Ok lets pick a simple system; 12vdc fan. Problem, fan does not run. Ok so now we know it is a fan not coming on, so the problem is "recognized. " So what do we really know about "where it is." A switch on a dash, the fan is located behind a panel near the co pilots feet, but is there more in that system besides a switch and fan motor? Could there be a "relay" in line between the switch and fan? Could there be a circuit breaker or fuse, between the switch and fan motor? All are valid questions and can be answered with a "sequence" of operation. "Sequence" of operation for the system above; 1.it is a 12vdc system so from the system circuit breaker, 12vdc is supplied to a switch and from the switch to the coil of a 12vdc relay then 12vdc passes through the contacts of the relay to the fan motor and the fan motor runs. Now we know the "how" it works, we can start to "localize" the problem. Starting at the circuit break we are going to check for 12vdc to be sure the switch is in fact getting power. Yes voltage is present. Then go to the switch and check for 12vdc, yes voltage is present on one side, then switch the switch to the run position and check for voltage. It is found that 12vdc is present on the out put side of the switch. Next stop is the relay coil, check for 12vdc at the coil of the relay, yes 12vdc is resent, then check the out put side of the relay, no voltage found, hmmm, interesting, now it is time to find out how the relay works, 12vdc goes to the coil of the relay then passes through the coil to ground and the relay energizes and the contacts are changed in state for open to closed, but the 12vdc power source is from some where else going to the 12vdc fan motor and not the switch on the dash. Now one must check the voltage patch the flow through the relay to the 12vdc fan motor, and find the "why" it is not present. So we have isolated the part of the 12vdc circuit that is not working to turn on the fan with the switch. Checking the "source" circuit breaker, it is found not to have 12vdc present. So the circuit breaker is the bad part, it must be replaced. Now switch on the dash switch and the fan motor runs. Great! you have fixed the problem, or have you? Did we look into the "why" the circuit breaker went bad? This part of trouble shooting is not always well defined and in fact may not be found. So that brings up the question, what must happen to make a circuit breaker fail? Lose connections are a cause. Bad ground is a cause, age of the part will contribute to the cause of failure. As you can see there can be several steps and items in a system even one as simple as this one. Trouble shooting can be VERY time consuming, but it has to be done to make a system work. Once you have been through a few troubleshooting procedures like this, you learn some short cuts here and there that helps to "cut" the time factor down a bit. Also a thing to remember. Nothing is set in concrete when trying to find out and repair what does not work. What I am trying to do here is show a process that is practical, saves time and effort and cuts the cost of a repair. Let's not throw money at something in hopes that is will make it run. You can sure go through allot of money doing that and still not find the problem let alone fix it. So with a few trouble shooting steps we have spent $3.00 on a part to make the system run, instead of spending $225.00 in parts like new switch? new fan motor, new relay and so forth. Yes it has cost the time to troubleshoot the system but is still cheaper on a repair bill than throwing money at some thing. Will stop here for this first post and wait a few days and answer any questions anyone may have. Ues I know it is a VERY simple system noted above, but there are a large percentage of people that do not have any idea what or how. Please keep that in mind when posting on this first post. Safe travels, Ralph and Charolette Fullenwider 84FC35 "Ruff Diamond" Duncan, Oklahoma