Community Forums

John Pacello · 06-11-2014, 11:31 AM

I am looking for a wiring diagram #0811-1236. I think I have a short between the L1 and L2 lines, I have continuity between the red and black lines at the transfer switch.
Onan, Quiet Diesel 7500, Wire Diagram 0811-1236,
Model 7.5 HDKAJ11451H, Spec: H, Serial #:I020416844
I hope someone can help.
Thanks
John

RV Wizard · 06-12-2014, 02:03 AM

The generator does not put out 220 vac between L1 and L2 but instead two lines of 120 volts. This may be the reason you are seeing the continuity between the two at the transfer switch. What lead you to look into having a problem with the generator? Give us as much detail as you can and we can be of much more help. Sorry I cannot help with the service manual on the generator.

John Pacello · 06-13-2014, 01:11 PM

RV Wizard, thank you for comments.

To further explain our problem...

I had 115V hooked up to the inverter charger over the winter. I had a small electric heater hooked up to maintain the MH at about 40 Deg. F. to keep the dampness out. We only had a few days of freezing this winter.

We were planning our first short trip, so I disconnected and moved the MH further up the drive closer to the garage where we have a 50 AMP outlet. "The loading zone."

After about a week typical service etc. I took the MH for an Oil change on the MH and the Onan 7500, and filled up with fuel.

We returned to the loading zone, I only wanted to keep the batteries topped so I plugged into 115V and it kept blowing the wall outlet and repeated reset. I then moved to another outlet and the breaker kept going off.

I started tracing where the short might be. I located the transfer switch under the foot of the bed, and found continuity, at the transfer switch, initially on the shore line, (not plugged in to 115V or 50AMP), the short coming through a small red wire placed under the black wires. I traced it to the genset side so I disconnected the black wire on the genset input to the transfer switch, and was able to plug into 115V with no problem. We took a 10 day trip with no incident, but no genset.

I tried to contact Onan, but there site is so well protected I have not been able to locate anything as simple as a problem and a suggested fix or a number to contact.

My next step is to open the junction box in the genset compartment and check for shorts in both directions, and run the genset and check the voltage at the junction box.

Your help is appreciated.

RV Wizard · 06-14-2014, 02:44 AM

Wish I could be of more help but generators are not my forte'. I can ask a guy at work that may know the answer off the top of his head but then again may have to do some research. Will let you know what I find out.

94-Newmar · 06-14-2014, 04:59 AM

John, attached is a diagram showing the AC layout.

The HDK series is an inverter controlled output type.. typical 8 pole permanent magnet, 3-phase stator. I'm confused by the "small red wire" you have found to be the problem. Did you remove only the small red wire from the transfer switch? That wire certainly cannot run back to the generator output - you should have 2 black (HOT) and depending upon how Gulfstream wired it, either one or both white (NEUTRAL) and of course the green (GROUND). I suggest that small red wire may be to something else such as an EMS or for a meter/panel elsewhere.

Does the genset run without setting an error code and shutting off?

With the genset off obviously, At the front corner, top of the genset is a small cover where the AC lines connect. Remove that cover and inspect that wiring well. It is not uncommon for those to work loose. With the genset running (if it runs) using a voltmeter check across either BLACK and either of the WHITE. You should see ~120VAC across either pair, but you will not see 240 between the BLACKS. You will see continuity between the BLACKs.

Remove the inspection cover just above your START/STOP switch reach in and follow the wiring to the breaker - those leads are connected with .250 spade connectors and are notorious for working loose.

John Pacello · 06-15-2014, 11:37 AM

RV Wizard and 94 Newmar thank you for your suggestions, I am a little tied up today with Fathers Day.

Tomorrow I will take a picture of the transfer switch & the red wire, and get the model number and make of the transfer switch.

I will also do some more Multi-meter tests

Thanks again

John