jcbett Report post Posted February 5, 2016 Need help to test the Battery Boost Combined Relay. We bought a used 2003 Safari Cheetha 37 DP. Have been repairing many of the systems and running down the circuits and which bank they are running on. Ran down the chassis bank several time by leaving the LP Valve on.(did not know it would be on the chassis battery) I was unable to jump start with the Battery Combine or Boost circuit. I think the relay might be burned out. Replaced both banks with new batteries but want to test the relay to see if it works. I have meter but don't know what should read what when. If someone might explain to me what steps to take, I would be grateful. Jim Blodgett 2003 37 Safari DP Share this post Link to post Share on other sites
wolfe10 Report post Posted February 5, 2016 Jim, At the battery combine/boost relay, check voltage at each of the two large lugs. If batteries are not combined, voltage should be different. If almost the same, turn on the head lights for a few minutes to drop chassis battery voltage so it will be enough lower than house bank (assuming plugged into shore power) that you can see a measurable difference. Turn on the boost switch-- if momentary, have someone hold it while you recheck voltage at the two large lugs. If working, the voltages will be exactly the same. You should also hear the relay click in when activated. If voltages not the same with boost activated, could be either a bad relay or lack of the signal from switch. The relay will have either one or two small wires/terminals. If one, it is the positive signal wire/terminal from the switch. And ground would be through the body of the relay. If two small terminals, the second small one would be to ground. With the boost switch activated you should have 12 VDC positive on the signal wire. If not, trace fuse/wiring/switch. The other test: You can then take a small wire (not going to carry many amps) from either large lug to the positive signal terminal. That should activate the relay. Share this post Link to post Share on other sites
abyrd Report post Posted February 5, 2016 You might want to chase the wiring to make sure that the power source for the boost relay feeds from the coach battery bank not the chassis battery.. Jim Share this post Link to post Share on other sites
jcbett Report post Posted February 5, 2016 Brett, Thanks for your information, will be my Saturday project. Jim Blodgett Share this post Link to post Share on other sites
abyrd Report post Posted February 6, 2016 I just installed a Smart Battery Isolator (Cole Hersee) to replace my boost relay.It automatically isolates the coach and chassis batteries when both batteries are below 12.7 volts for 1 minutes and it automatically closed if either battery bank reaches 13.2 volts for 2 minutes.It has an override feature (boost) that allows you parallel the two battery in an emergency and it also has a lead for a indicator lamp to let you know when the isolator contacts are closed.I purchased mine on Amazon.com for just over $100, 5 minute job to replace the old relay.Jim Share this post Link to post Share on other sites
