klparker Report post Posted January 28, 2016 Generator works fine until AC is started; then it surges and turns off. Just changed oil, replaced all filters and it does the same thing. Generator has 400 hours on it. Any ideas? Share this post Link to post Share on other sites
wildebill308 Report post Posted January 28, 2016 Did you clean the spark arrester? Did you give it time to warm up before applying a load? Bill Share this post Link to post Share on other sites
garyreed Report post Posted January 28, 2016 I hate to ask, do you have 1/4 plus in the fuel tank. how long since it was last run and did it run good then? How old is the coach? Do the fuel lines and clamps look good between the genset and the coach frame? No kinks or wet spots Gary Share this post Link to post Share on other sites
tbutler Report post Posted January 28, 2016 When your generator shuts off there should be a series of flashes of the light on the start switch. The pattern of those flashes indicate the problem. There should be a listing of the fault codes in the back of your generator manual. The series of flashes are in two bursts, the first burst is likely three flashes and the second may vary. If you get three flashes a pause and then six flashes, that would be fault code 36. Your manual will tell you what a fault code 36 is. If you don't have your manual, get the code and then call Cummins for assistance. The link will take you to their service locator where you can find the nearest service center. Having the fault code will tell them what the problem is and they may be able to tell you what to try to correct it. Everything from low coolant, overheating, low oil pressure, voltage irregularities, etc. will have a code. I made a copy of the codes from the manual, laminated it and keep it in the side pocket by the drivers seat. Share this post Link to post Share on other sites
jleamont Report post Posted January 28, 2016 klparker, Do you have an auto start/stop option on your generator? Make sure your auto stop is not activated. If mine is set to auto stop at a certain battery level my generator will start up with the manual switches and run for 1-2 minutes and shut off just as the A/C units were about to start up (its only looking at the battery level not the load). I thought I had a problem then it dawned on me that the Xantrex panel had no idea the A/C units were on standby. Sounds crazy but its engineering at its finest! Share this post Link to post Share on other sites
klparker Report post Posted January 28, 2016 There is plenty of fuel, generator is warmed up, and works all appliances while AC is not running. Turn AC on with no other appliances, etc. engaged, generator runs, AC comes on for a few seconds then there is a surge and the amps shown on panel rises above 50 and the generator cuts offs. Code shown is blink pause blink, blink, blink, blink which appears to be 14 fault code: (controller not able to regulate rated frequency). Corrective action: Reduce number of appliances, especially when AC and battery charger is running. There is nothing else running in the coach when the AC is engaged. Did not clean spark arrestor, fuel lines, etc. look good. 2001 Itasca Horizon Share this post Link to post Share on other sites
hermanmullins Report post Posted January 28, 2016 Kl, How many amps does your ac pull on shore power? Herman Share this post Link to post Share on other sites
dickandlois Report post Posted January 29, 2016 Klparker, You mentioned that the generator quits when you start the AC. Do you have more then one AC unit? Should you only have one, I would check the compressor starting caps and motor starter module. If you find no problems in that area check the compressor for a shorted winding. I have a feeling the AC compressor is drawing a high current, but if that is the case you might also have a defective circuit breaker in the 120 volt circuit breaker box. Try turning it off and back on - if it feels different then the others have it tested, because a good breaker should trip if the AC is drawing a high current. Let the group know what you find or the service tech finds. Rich. Share this post Link to post Share on other sites
klparker Report post Posted January 29, 2016 Coach has 2 stage heat pump. AC has 2 compressors, both work great when 50 amp applied (no problem with heat running via generator). When lower than 50 amps shore power, panel display indicated @18amps applied. Even with 110 and just appliances running, frig & TV, the AC works fine. Share this post Link to post Share on other sites
hermanmullins Report post Posted January 29, 2016 KL, Do you have a way to watch the amperage draw when you are running the generator and then turn on the A/C? It would be nice to know what the amperage draw is when the compressor starts. You may need to contact both the A/C Mfg. and Onan. Good luck. It may be cool now, but it want be long before you will need the A/C everyday. Herman Share this post Link to post Share on other sites
wolfe10 Report post Posted January 29, 2016 Sure, I guess it could be an A/C unit issue. But with the A/C working properly on shore power the generator would be my first "point of diagnosis" Actually, the first thing I would do is change the fuel filter. It is during high-demand times (picking up a heavy load for instance) that restricted fuel flow will cause issues. Share this post Link to post Share on other sites
dickandlois Report post Posted January 29, 2016 Brett, the OP mentioned the unit was serviced not long ago. Good to know that things work fine on shore power. kind of takes the main wiring out of the picture. With new filters and oil change recently performed, Was the fuel filter replaced at the time? Good point. Did the unit operate properly with a full load after the service? Could the fuel line have been compromised is some way? Sure sounds like there where no issues before the service. No mention of error codes. I might be reaching a little, but there is a small possibility of a loose connection in the J Box connections where the generator wiring is connected to the coach wiring before the transfer switch. Rich. Share this post Link to post Share on other sites
manholt Report post Posted January 29, 2016 Rich 1. Fuel restriction 2. One, two or three AC units on at same time? Or....that was asked by you, Rich. So far, we guess! Carl Share this post Link to post Share on other sites
klparker Report post Posted January 29, 2016 Everything works fine on shore power. Everything works fine on generator except AC, then it surges above 50 amps. As explained, AC operates via heat pump. Generator oil, fuel, air filters were all changed; however, prior to and after the AC makes the generator surge and cut off. Share this post Link to post Share on other sites
manholt Report post Posted January 29, 2016 kl. Do you have 2 AC 15,000? Or another size configuration? Heat pump should only come on when your on electric heat, not AC! Do you have the choice to put the AC's on line one at a time? Also, when you start generator let it warm up for 2-3 minutes with "no load on it", same with shut down, turn everything off and let gen cool down for 2-3 minutes or more! Carl Share this post Link to post Share on other sites
wildebill308 Report post Posted January 29, 2016 Everything works fine on shore power. Everything works fine on generator except AC, then it surges above 50 amps. As explained, AC operates via heat pump. Generator oil, fuel, air filters were all changed; however, prior to and after the AC makes the generator surge and cut off. It should only surge/exceed the usual load on start up. My units stage the load so it doesn't hit all at once. I don't know if it will help but I seem to remember a post about using a "hard start capacitor" to help with the start up of the AC units. You might do a little research on that. Bill Share this post Link to post Share on other sites
manholt Report post Posted January 29, 2016 After re reading all of kl's answers, I'm inclined to think that a 7.5kw gen is not big enough to run the AC's and everything else. My 37' had 2 AC 1500's and residential fridge along with micro/convection...8kw gen! My current coach has 3 AC 1500's and all electric, with a 10kw! Carl Share this post Link to post Share on other sites
klparker Report post Posted January 29, 2016 Think the problem is solved! Started generator let it warm up, turned off the battery charging via power panel, started AC and it started slowly, surged to 45 and settled on 11 amps. When compressor came on it went to 45 and back to 11 each time, but it never turned off. Even with AC running we tried TV, and a couple of lights and no problem with generator. Thank you all for the input/advice. KL Parker Share this post Link to post Share on other sites
wolfe10 Report post Posted January 29, 2016 As mentioned, a hard start capacitor on each A/C will materially reduce the initial amp load. They are NOT expensive or difficult to install (once on the roof). Share this post Link to post Share on other sites
dickandlois Report post Posted January 30, 2016 KL, Glad you found a way to start the CA units. The information you posted,regarding the current surge comes real close to the max current the generator can supply per load leg. Adding a hard start cap to each of the AC Compressors will help, but it might only mask an issue with the OEM AC starting circuit. The capacitors and the motor start module are not that expensive - think I missed the Year your coach was built. I have replaced the starting caps on my AC units after one of them failed to start. NOTE! In the process I found a badly burned section of wire that connected the 120 volt AC power to the main Start capacitor and the connection had a large amount of coronation at the connection. This also caused a higher resistance. That resistance also reduced the starting current to the start cap. A capacitor is a current passing device not a voltage passing device. When the cap fails the Motor does not get the kick it needs and the motor then tries to draw more current then the run circuit can supply. The next thing that happens is the circuit breaker trips or the generator safety circuit kicks in. Keep the current below the trip point of the generator the way you did,by disconnection the charger/Invertor . Things work for now. You might want to look or have a service tech check for the same problem on your units Rich. A note to others reading this post ! This coach is equipped with what sounds like AC / Heat pump systems not exposed to hail damage. If you have been in a hail storm - The hail can damage the condenser fins on a roof unit. This causes the high side pressure on the AC system to increase. The higher pressure causes the compressor motor to draw more current. The increased current will then burnout the motor. There is a maximum pressure level for all air conditioning system. So if your not one that likes or can walk around on top of your coach to check for damage. An AC tech with the proper information and training can test the high and low side pressures and see if they are out side the design limits and if they are have the condensers fins visually inspected. Might save you a lot of money out of pocket if your insurance does not cover replacement. Share this post Link to post Share on other sites
wildebill308 Report post Posted January 30, 2016 Kl please add your coach to your signature as it helps to get good answers. See my sig as an example. Bill Share this post Link to post Share on other sites
hermanmullins Report post Posted January 30, 2016 KL, Thanks for the update. Glad you solved your problem. Herman Share this post Link to post Share on other sites
manholt Report post Posted January 30, 2016 kl. Same here. But, I think you still have a issue with your AC unit. Good Luck Carl Share this post Link to post Share on other sites
kaypsmith Report post Posted February 1, 2016 A little clarification on some misguided thoughts concerning 50 amp service being 100 amps total on the generator may be in order here. It is true that on shore power a 50 amp 240 volt circuit does have 100 amps available at the cg box, but on generator power, you must take into consideration the running watt figure that the generator is rated at. A 7500 watt Onan generator is only 62.5 amps available at 240 volts, which is 31.25 amps on each side "L1 and L2", 120 volts on L1 and 120 volts on L2 for a total of 62.5 amps 240. To calculate this, you need to take 7500 watts, divided by 2 = 3750, this is the total watts available per 120 volt side, then to break this down to amps, you must divide 3750 by 120 = 31.25. Using these same calculations, Carl's 10,000 watt generator is 41.6666666667 amps per 120 volt side or a total of 83.33 amps. In other words, you will need a 12,000 running watt generator to provide the same current as a 50 amp cg circuit. Please also note that generators today usually have two numbers of watts showing, in this case the first labeled with the higher number is only surge watts, which means that number will be provided for a very short period, usually one or two seconds, then the second number is the one that is significant for actual running continuously. Hope this helps to understand why the generator was most likely shutting down under a larger load. Also as mentioned by other posters, a hard start capacitor to replace the existing capacitor in the ac units might help in the future with the situation, as its purpose is to lighten that higher surge load on initial startup. Share this post Link to post Share on other sites
JHanson907 Report post Posted February 1, 2016 KLPARKER - We have a 2005 Winnebago Vectra, which I believe is similar to your Itasca Horizon. The AC unit is in the basement on your RV? That's where ours is. Your starting amps on the AC seems very high. I have watched ours run, on the panel, and the amp load on AC compressor start is rarely higher than 38 amps even on very warm days. We can run both our AC compressors, the battery charging circuit, lights, refer on electric, etc., w/ our 7500 Onan (diesel) and have no problems at all. The generator just hums along happily making electricity. I'm not sure you have necessarily solved your problem. Some of the other writers mentioned some things to look at to help determine if you have excessive resistance w/ wiring, connections, corrosion, etc. I highly recommend following up w/ those ideas as you should not have to make "adjustments" as you have been for basic systems to operate. Good luck and happy RVing! Share this post Link to post Share on other sites
