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Old 06-13-2012, 02:39 PM   #29
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Originally Posted by Kathryn View Post
I would think the fuel saved by less strain on the engine in the heat would pretty much cover the fuel used by the gen

Yes, Kathryn, even though I have a gasser, it certainly is that way for me.

My coach:

I found that running the chassis a/c shaves about 1 mpg off.
A 500 mile trip at an average of 50 mph would mean 10 hours driving. 500 miles divided by 7.5 mpg = 67 gallons (no chassis air)
500 miles divided by 6.5 mpg =77 gallons. (chassis air)

Difference in running the chassis a/c is + or - 10 gallons of fuel.

Same trip, 10 hours of Genny a/c at .60 gallon per hour is .60 x 10 = 6 gallons of fuel.

So its cheaper to for me to run the genny in high temperatures. I was driving in 100 to 105 last June and July.....ugh.... And the last 3-4 hours of driving I had to run BOTH genny and chassis. It was late in the afternoon heading west, sun grilling the front of the coach, just couldnt get enough cold air up front, so I had to run the chassis air....

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Old 06-13-2012, 02:45 PM   #30
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Originally Posted by 336muffin View Post
When traveling we run the gen with the AC's, water heater, fridge all on the gen. If you break it all down it's cheaper than the dash AC, propane for WH, and Fridge. Just my opinion
Does that consider the lifespan and replacement cost of a generator?

BTW - I'm not following the advice of this forum and running the genset / coach AC. However, I'm not sure it's less expensive long term.

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Old 06-13-2012, 03:07 PM   #31
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"Does that consider the lifespan and replacement cost of a generator?"

I bought my rig 10 years ago with 26 hours on the generator.

We average about 6,000 miles per year of travel, and much of the time have the generator running while we drive. Our annual use seems to be normal for most MHs.

The generator now has 650 hours of use including some extended boondocking events.

I would guess about 1/5 of the generator's useful life has been used or even less in the last 17 years. At this rate I will be over 100 yrs old when it dies.
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Old 06-13-2012, 03:22 PM   #32
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Most of the problems I have heard about gen is that they were not run enough. We are on our fifth coach and have never had a gen issue. The most expensive repair was a lift pump. I have heard some expensive repairs on some. We travel with ours set to auto start and the thermostats comfortable.
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Old 06-13-2012, 04:09 PM   #33
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Originally Posted by bigdomino View Post
Will be leaving Nashville this coming Friday and heading toward Denver. I understand it will be 95 Is weekend. I have a 2008 Monaco Knight with an isc engine in it. I have never driven it in 95 plus heat. It normally runs between 180 and 188 degrees. After driving all day the trans will run around 172 degrees. Should I expect to see the engine and trans run warmer or the same?


I'll be a few days behind you! I'll keep some iced tea cold and a look out for ya!
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Old 06-13-2012, 07:50 PM   #34
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Some people like to hang a curtain behind the driver's area. You can't see out the back anyway, so that's not a problem. Having the cabin area blocked off from the rest of the coach is a big help in keeping the dash AC contained to a small area.

Just a thought,
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Old 06-17-2012, 09:21 PM   #35
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Another vote for the genie/house air method. We are always driving in the heat (So. Tx) and it is the only way to stay relatively cool.
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Old 06-17-2012, 10:15 PM   #36
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Back to the OP and his 08 knight (which is a 360hp ISC with a rear rad BTW...)

Our has behaved the same out west as it did back east. 185... I saw 192 on the alladin on a coupl hard climbs in utah, outside temp well over a hundred. Trans runs 10 degrees less always. No problem at all. Never turned the dash air off. I run the genny and roof air if the kids complain, but the dash air does a pretty good job keeping things cool.

OP, u got nuttin to worry about!
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Old 06-17-2012, 10:27 PM   #37
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A couple weeks ago I did an experiment. Running at 60 mph, no wind and flat terrain my UltraGuage said my engine temp was 199.4. Outside air temp was about 80 degrees.

I then turned on the engine air conditioning and the temp went up to 203.2.

I then turned off the A/C and the temp dropped back to 199.4.

It took about three to four minutes for the temp to stabilize.

I did that three times and the results were consistent.

So I figure about three degrees in engine temp to run the A/C.

In really hot weather I turn off the dash air and use the generator to run the coach air.
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Old 06-18-2012, 05:18 AM   #38
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On a front engine unit the dash air will probably add to the load on the engine cooling system because the A/C condenser is placed in front of the radiator and transmission cooler. On a rear engine unit, side or rear radiator the condenser for the A/C will be located away from the cooling system radiator and have it's own electric cooling fan or fans and will not contribute to the cooling system load. Just to be clear, the engine driven A/C compressor will load the engine and contribute some minor heat to the engine cooling system. Probably not noticeable on the dash gauges.
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Old 06-18-2012, 07:52 PM   #39
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Today we drove from Las Vegas to Lee Vining, Ca by way of Nevada 359 over a 7600ft pass. Outside temp was in the high 90's all day. Engine temp varies between 180 and 207. Trans temp between 180 and 195. It is a 2012 ISC380 rear radiator. The engine fan comes on at about 207 and the temps drop right down to the 180's. Then it climbs up to just below 210. Fan comes on and the process repeats. This is the same behavior as in cool weather on flat ground. We have 11000 miles since September when we took delivery. It has been very consistent in all kinds of terrain and weather.
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Old 06-18-2012, 09:17 PM   #40
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To jimm68.

I have a 330 Cummins. It was a 2007 engine. I have a early 2008. No smog converters either.

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Old 06-19-2012, 11:26 AM   #41
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Originally Posted by bigdomino View Post
Will running air in bus, not house air, make the engine run warmer?
See commnet above "If cooling system is working properly"

Perhaps 1 or 2 degrees, But not enough you should notice.

Engine temp is controlled by a device called a Thermostat, So long as you are moving, and enough air is passing the radiator, and it's not like 200 degrees in the shade (Ridiculous temp I know) you should not have a problem.

I have spoken with quality control folks at a few manufacturers.. You really don't want to know the kind of testing they do on those engines and you would NOT wish to drive your rig under those conditions.

If it is working as designed, the tires will melt before the cooling system fails.
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Old 06-19-2012, 02:09 PM   #42
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Thanks to everyone on this thread ... we are new soon to be fultimers ... just purchased a 1993 royal coachman ... 460 ford engine with added grears for downshifting (not yet sure what that is all about) ... just wanted to let you know how helpful this info about running the gen. for the air condition, fridge, and pumps ... great to know we will be comfortable ... what about when boondocking ... is the .6 per hour the same?

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