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TallPaul · 12-23-2007, 03:11 PM

It's a Generac Q55-G in a 1990 Gulfstream Class C. Generator ran fine a couple weeks ago. Today I went out to work on the motorhome and thought to exercise the generator, so I turned it on. Then I went to run a 110 volt vacuum and it would not go on. There was no 110 power. Motorhome has an automatic switch between generator and plugging in. I noticed the 20 amp breaker was off on the generator and so switched it on. Still no power. Then I cut the generator off and plugged in. Plugged in I had 110 volt inside.

Next I went where the generator wireing comes in the coach. There is 1 black, 1 red, 1 green, and 2 white wires. The black was capped off and not in use (was when I bought it and when gen was working). The 2 whites were connected together. Running the generator I got 6 volts AC. Then I figured maybe it's a DC generator, but it read 0 volts DC. The red wire slightly touched ground and there was a little spark, nothing major. Then it reas about 3 volts AC.

Is the dynamo burned out on my generator? Or is there some devise that maybe is blown that I can replace cheaply? I have visions of a whole new dynamo which I imagine at the low end is about $1000 installed!

This is ironic as I had a motorhome from '01 to '6 that had no generator and traded to a Class A with a generator, had nothing but trouble with that generator (about 800 hours on it), so traded in again and go the Gulfstream. The Generac on the Gulfstream has all of 120 hours on it. Was about 50 when I bought it last May.

I sure hope there is a simple fix.

Oh by the way, maybe I read the wront wires (I HOPE) because they seem a bit small for incoming power from a 5500 watt generator. The wire looked no better than maybe 14 gauge (hard to tell as stranded wire). Would have expected something more like 10 or 12 gauge, so maybe I got the wrong wires? But they do come up throught the floor above the generator and the colors match what the book says, and there is only one lead up from the generator to the coach that I can find, though there are other larger looking wires around, maybe from house battery to starter, which would make sense.

TallPaul · 12-23-2007, 03:11 PM

It's a Generac Q55-G in a 1990 Gulfstream Class C. Generator ran fine a couple weeks ago. Today I went out to work on the motorhome and thought to exercise the generator, so I turned it on. Then I went to run a 110 volt vacuum and it would not go on. There was no 110 power. Motorhome has an automatic switch between generator and plugging in. I noticed the 20 amp breaker was off on the generator and so switched it on. Still no power. Then I cut the generator off and plugged in. Plugged in I had 110 volt inside.

Next I went where the generator wireing comes in the coach. There is 1 black, 1 red, 1 green, and 2 white wires. The black was capped off and not in use (was when I bought it and when gen was working). The 2 whites were connected together. Running the generator I got 6 volts AC. Then I figured maybe it's a DC generator, but it read 0 volts DC. The red wire slightly touched ground and there was a little spark, nothing major. Then it reas about 3 volts AC.

Is the dynamo burned out on my generator? Or is there some devise that maybe is blown that I can replace cheaply? I have visions of a whole new dynamo which I imagine at the low end is about $1000 installed!

This is ironic as I had a motorhome from '01 to '6 that had no generator and traded to a Class A with a generator, had nothing but trouble with that generator (about 800 hours on it), so traded in again and go the Gulfstream. The Generac on the Gulfstream has all of 120 hours on it. Was about 50 when I bought it last May.

I sure hope there is a simple fix.

Oh by the way, maybe I read the wront wires (I HOPE) because they seem a bit small for incoming power from a 5500 watt generator. The wire looked no better than maybe 14 gauge (hard to tell as stranded wire). Would have expected something more like 10 or 12 gauge, so maybe I got the wrong wires? But they do come up throught the floor above the generator and the colors match what the book says, and there is only one lead up from the generator to the coach that I can find, though there are other larger looking wires around, maybe from house battery to starter, which would make sense.

Joe-K · 12-23-2007, 05:48 PM

I had a generac generator in a rig I had quite a few years ago. Honestly, I don't remember much about to help troubleshooting, but I do know that I had found the service manuals on line for the generator. Their manuals contain great step by step troubleshooting.

I think this is your model in the following link. Hopefully it will help with the troubleshooting.

Quietpact 55 service manual

RV Wizard · 12-24-2007, 01:26 AM

TallPaul, you can check the voltage at the transfer switch itself for the generator output. If you do have power comming from the generator but it does not make it into the coach then you have a problem with the Transfer switch. If you do not have power coming from the generator and the circuit breakers are good then you might want to check the rings and brushes on the generator. How often do you exercise it?

TallPaul · 12-24-2007, 04:38 AM

Joe-K: [EDIT: The manual is fascinating. Lot of good information, but mostly stuff that is beyond me in time or skill.]

RV Wizard: [EDIT: I believe the transfer switch is in the electrical center. I am checking the wiring where it comes through the floor, about halfway to the electrical center.]

The motorhome got 9700 miles use and about 50 hours on the generator in it's first seven years of existence. So I figure the previoius owner did not exercise it much if at all. I know that after 2004 it mostly sat. Maybe that is the problem. I will confess I was not running it more than once a month at best. I did not realize the exercise had to do with the dynamo. Well if the springs and brushes are bad I'd guess it's going to have to be dropped to replace them. That is beyond my time/ability. Looks like it will have to go in to the shop.

What do you recommend for exercising frequency?

EDIT: [Here is an idea. The manual Joe-K posted shows that the black wire is a second 110 volt lead (or can be used with the red to form a 220 volt circuit) I wonder if the black wire is still putting out good voltage. If I start the generator and find 110 volts off the black wire, what is to stop me from using the black wire instead of the red wire?

There are two circuit breakers on the face of the generator, a 20a and a 30a. I am thinking the black wire will be associated with the 30a. If so, would I have to switch those breakers to limit the circuit to 20, or is 30 okay?]

Sunny · 12-24-2007, 08:56 AM

TallPaul
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">EDIT: [Here is an idea. The manual Joe-K posted shows that the black wire is a second 110 volt lead (or can be used with the red to form a 220 volt circuit) I wonder if the black wire is still putting out good voltage. If I start the generator and find 110 volts off the black wire, what is to stop me from using the black wire instead of the red wire?

There are two circuit breakers on the face of the generator, a 20a and a 30a. I am thinking the black wire will be associated with the 30a. If so, would I have to switch those breakers to limit the circuit to 20, or is 30 okay?] </div></BLOCKQUOTE>

The Red wire should be on the 30 amp breaker check it out turn it off and back on. The black wire should be on the 20 amp breaker and is used most of the time for a 2nd AC.

Tom

TallPaul · 12-24-2007, 03:48 PM

Good info Tom.

Say, here is something very interesting. The manual Joe-K posted on page 6 states that the house battery provides Field Boost current on startup, when the engine is cranking. This is to flash the field and ensure that sufficient pickup voltage is available on every startup to turn on the voltage regulator and build AC output voltage. Then there is a note that "loss of the field boost function may or may not result in loss of AC power winding output. If torot residual magnetism alone is sufficent to turn the regulator on loss of field boost may go unnoticed. However, if residual magnitism alone is not enough to turn the regulator on, loss of field boost function will result in loss of AC power winding output to the load. The AC output voltage will then drop to a value commensurate with the torot's residual magnetism (about 7-12 VAC)."

The last time I started it and it worked, my battery was so low (2 lights) I had to plug the motorhome in for a minute before the generator would crank over, but that time it worked. This time the battery seemed okay (4 lights down to 3 after maybe 20 minutes of running lights and the generator startup).

Again, it's a shot in the dark, but maybe I need more battery voltage to start up?

TallPaul · 12-25-2007, 02:57 PM

Bingo Sunny. I thought I had tried to turn the breakers off and back on last night, but can't remember for sure. Anyway, tonight I fired it up to check the black wire and once started I checked a 110 volt nightlite and it would not go on. Then I went outside and flipped both breakers (30 amp and 20 amp) off and back on. Went inside and the nitelite works. I have 124 volts on black line and 124 volts on the red line. All is well, so it seems.

I just don't understand what happened yesterday though. Would hate to get out on a trip and have it not work again. Are the breakers such that they can go off witout the handle moving to off? That would explain a lot.

Also, RV Wizzard, how often should I exercise the generator? How long? Summer it seems 10 to 15 minutes is enough to get the oil to full operating temperature, but winter more likely half an hour.

I'll point out one other oddity. On our first trip last may, one time the gen would not shut off from the inside switch. Always worked before and since though.

Thanks, all. Even if there is nothing wrong with the gen, it was a worthwhile thread because I learned a lot about how it is hooked up and now have the repair manual.