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cb1000rider · 07-25-2012, 08:06 PM

Man, we've had a helluva trip from TX to MI and back....
We're in Missouri. It's 106 on the road. This is causing my Onan Marquis 5500 to overheat (apparently) and shut down.

Yes, I'm sure it's an overheat.. It'll run just fine on the road for 1-2 hours (depending on load). As soon as it gets hot during the day, it's done and won't restart for 30-40 minutes. Before shut down, the RPM will vary.

If I leave it running with the cargo bay open, it seems to do OK.

This has necessitated the purchase of 6500 watt generator as I can't operate in the heat without coach AC... So, we've got that wired in and sitting on the trailer hitch.

Anyway - my first question is:
1) How effective are your 13.5K BTU or similar AC units on the road? As near as I can tell, these ours are functioning normally - about a 20 degree drop in ambient temperature. Right now, I can only run one of them, so we're looking at about 85 degrees in the RV running both the coach and chassis ACs.

Mr_D · 07-25-2012, 08:18 PM

We have a 8.0 KW diesel liquid cooled gen set. In Yuma in 95° weather we did just fine on one 13.5 heat pump. But our rig is better insulated than most, we have dual pane windows and an optional roof insulation package. We were plugged into 50 amp shore power too so we didn't run the gen.

cb1000rider · 07-25-2012, 08:29 PM

We have a 1999 Holiday Rambler Vacationer.. Aluminum sides, fiberglass roof. I imagine that it's as well insulated as most low-end Class-A RVs.

It has a 6.8L V10, which is of course situated up front in a manner that incurs heat on the doghouse and as a result, the coach itself.... So stopped, we've got no problem with a single AC keeping up, although I can't think of a time where I had it in the sun at 106 degrees.

The AC unit seems to loose efficiency while driving, which makes no sense, so I've attributed it to heat gain from the V10 and perhaps the air cooled genset...
Regardless, one 13.5K unit isn't getting it done..

Just wondering if this is a common issue with gasser Class-A RVs when it's really hot out...

bluepill · 07-25-2012, 08:33 PM

Quote:

Originally Posted by cb1000rider

As soon as it gets hot during the day, it's done and won't restart for 30-40 minutes. Before shut down, the RPM will vary.

If I leave it running with the cargo bay open, it seems to do OK.

.

If this is a gasoline genny, it sounds like a fuel problem - most likely vapor lock somewhere in the genny compartment. Possibly you could hook up a 120 volt electric fan that would move hot air out of there.

cb1000rider · 07-25-2012, 08:50 PM

It's an overheat problem. Vapor lock...maybe... I suspect not as it wont restart at all for 30-40 minutes, I assume as we've triggered an over temp switch and heat soaked.

I'll get the genny sorted out...

I am, however, curious to know how coach AC's do in gasser class-A's when it's really hot...

CharlieTwo · 07-26-2012, 04:43 AM

I am leaning towards the vapor lock problem. You have a varying speed of the motor before shut down. A switch is just on or off. Keep an eye on your tires. Semi's are blowing them all over the place. Not a good thing to hit. The road temp will be a lot higher than 106.

vincee · 07-26-2012, 07:36 AM

Last summer parked at our campsite in north central PA it was 107 outside and our single 15,000 ac kept the rig as cool as needed. Never have tried it while on the road though.

rvguy40 · 07-26-2012, 11:14 AM

I run both my 13.5's on the road regularly. The genset does a fine job even when the temps creep over 100 here in east TN. I leave them set at about 70. The front A/C rarely, if ever, cycles off. The rear, however, cycles off regularly. There's ALOT less glass in the rear obviously... but they maintain a cool, comfortable temp for traveling regardless. I find I get nominally better mileage running the genset than the dash air.

two2go · 07-26-2012, 11:58 AM

We have the basement air/heat pump. On generator or 50 amps running both compressors, we can maintain 20-25 deg. differential. On 30 amps running one compressor, maybe 15 degrees. The amount of sun exposure makes a big difference (i.e., shade helps)

PatStab · 07-26-2012, 01:37 PM

We are fine sitting in a campground. We just took our old American Eagle to Indiana and back. It was horrible outside, 108 on the temp. The back was nice and cool, the front pretty warm. I haven't put film on the windows yet and they are single pane.

We had ours go off several times. We have an 8k diesel genny and it was fine. However the breakers were getting hot and flipped, we took the old units out and put in 2 15k AC units.

The breakers are under the bed so I opened the door still did it after a few hours. I had brought a cheap double window fan and we plugged it in and directed it to the breakers, issue solved.

We are going to put a grid in the door instead of solid wood, also going to make ventilation under the bed better.

However in the front I think we may have to add a fan but how many times is it going to be that hot? It was just horrible out. We don't think this will happen in the future but since it was our first run we don't know yet.

Maybe it was your breakers getting to hot also?

96 Wideglide · 07-26-2012, 02:01 PM

Quote:

Originally Posted by rvguy40

The front A/C rarely, if ever, cycles off. The rear, however, cycles off regularly. There's ALOT less glass in the rear obviously...

hmmmmm. I always thought both of mine were hooked to the same thermostat. On mine, a little round plastic unit, on the wall just outside the bedroom door.

JohnBoyToo · 07-26-2012, 02:11 PM

you might tyr shutting off part of the coach and/or doing anything to keep the sun outside

Maybe reflectix on the sunny side windows ?!? or at least the blinds down...

Senior Chief · 07-26-2012, 03:34 PM

I have to second the use of Reflectix, especially while you're moving. This will reduce your interior temps a LOT.

rvguy40 · 07-26-2012, 05:00 PM

Quote:

Originally Posted by 96 Wideglide

hmmmmm. I always thought both of mine were hooked to the same thermostat. On mine, a little round plastic unit, on the wall just outside the bedroom door.

You may have one thermostat that controls both zones. Mine's still old school... has 2 seperate thermostats.. one in the hall near the dinette, and one in the bedroom. The little round doohickey you're speaking of is most likely the temperature sensor for the thermostat...