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Old 04-19-2011, 06:18 PM   #15
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Fan clutch should start to engage about 170' AIR temp and be fully engaged at 195' AIR temp. This does correspond closely with the water temp. from my experience with my MH. If your thermostat is letting in coolant that is around the 170' mark into the radiator your fan clutch may come on too soon.
Last fall with the fan clutch off we would get about 8 to over 9 mpg, with the fan clutch on along with the a/c we would get 6.5 to 7.5 mpg. This was on a 2,600 mile trip so got to check many tanks of fuel for mpg.
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Old 04-20-2011, 09:20 AM   #16
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Fan clutch should start to engage about 170' AIR temp and be fully engaged at 195' AIR temp. This does correspond closely with the water temp. from my experience with my MH. If your thermostat is letting in coolant that is around the 170' mark into the radiator your fan clutch may come on too soon.
Last fall with the fan clutch off we would get about 8 to over 9 mpg, with the fan clutch on along with the a/c we would get 6.5 to 7.5 mpg. This was on a 2,600 mile trip so got to check many tanks of fuel for mpg.
A.C. alone will suck the gas down and of course the fan will draw some also, Fans can knock off about 20 horses (some less & some more) but that has been the average fan loss....
Just clean up the radiator air entry the best you can and enjoy the ride.

Jim
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Old 04-21-2011, 10:16 AM   #17
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We tried not running the a/c when the ambient temperature was up but if the fan clutch was engaged there was no noticeable difference in the mileage without the a/c.
My MH also has two 12" electric fans mounted to the a/c condensor. They do lower the pressure in the a/c system a little, but have little effect on coolant temperature.
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Old 04-21-2011, 11:22 AM   #18
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We tried not running the a/c when the ambient temperature was up but if the fan clutch was engaged there was no noticeable difference in the mileage without the a/c.
I'm sorta confused by your statement, Are you saying the fan consumed the same amount of power as the A.C.?

Known fact for me is 1 MPG is the loss while the A.C. is on and the fan will cycle in and out as needed, Hard for me to hear the fan since the insulation on the dawg house and surrounding area is so thick...

The reason I wrote the fan H.P. draw is approx 20 ponies is due to the size of the fan (17,18 or 19 inch) and the pitch of the blades.

Original fan on my 83 was only 5 blades and in our summer heat which can top 120* it didn't hack it for cooling....

Jim
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Old 04-21-2011, 11:59 AM   #19
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Mine has a flex fan.. lowers pitch the faster it turns.
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Old 04-21-2011, 12:07 PM   #20
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Mine has a flex fan.. lowers pitch the faster it turns.
That is so but it also draws less air.

Jim
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Old 04-22-2011, 01:51 PM   #21
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I could not document much variance in the mpg when the fan was engaged or when the fan and a/c were both engaged. Driving conditions could have been enough different to mask the a/c draw. When the a/c is on the electric fans also run so this may have some effect on the mpg. Might be limiting the percentage of engagement the fan clutch is in.
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Old 04-23-2011, 11:25 AM   #22
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I could not document much variance in the mpg when the fan was engaged or when the fan and a/c were both engaged. Driving conditions could have been enough different to mask the a/c draw. When the a/c is on the electric fans also run so this may have some effect on the mpg. Might be limiting the percentage of engagement the fan clutch is in.
Leadman, When I came home from Surprise Az one week ago the weather was warming up (90+) so I decided to exercise the dash air.

Worked fine and the engine temps rose about 10* which was expected but well below the 200* mark, The temp would bounce between 192* and 197* on the flat slab called the I-10.....

The preference is to close the door between the bathroom area and the main coach and crank up the genny and use the roof air, One A.C. will consume about 7/10 of a gallon of fuel per hour which IMHO seems cheap and with lower engine temps it is a win/win situation.

With both airs on the genny uses 1 GPH (measured) and it is a Onan 6500.....

Jim
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Old 04-29-2011, 05:12 PM   #23
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I guess I am lost here. You folks are saying that if you put in a 195 thermostat the fan clutch will not cut in as often as opposed to having a 180 stat? It would seem to me that having a 195 stat would allow the water to get hotter going into the radiator and thus having more heat coming off of the coils hence the fan clutch senses the higher heat and running more. Now with all of that being said I have had my radiator rebuilt a year ago and I do have a 180 stat in it and the fan kicks in as soon as the gage hits 181. What am I missing here? Confused.........?
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Old 04-29-2011, 05:23 PM   #24
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I guess I am lost here. You folks are saying that if you put in a 195 thermostat the fan clutch will not cut in as often as opposed to having a 180 stat? It would seem to me that having a 195 stat would allow the water to get hotter going into the radiator and thus having more heat coming off of the coils hence the fan clutch senses the higher heat and running more. Now with all of that being said I have had my radiator rebuilt a year ago and I do have a 180 stat in it and the fan kicks in as soon as the gage hits 181. What am I missing here? Confused.........?
Just leave yours alone...Sounds good to me.
Do you have "Digital or analog guages" in your rig?..I'm curious about the fan kicking in at 181*, My fan kicks in around 212* and on my dash analog the is the center stripe.....
What year is your rig?

Jim
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Old 04-29-2011, 07:18 PM   #25
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Well Jim, I have after market analog gauges. As soon as the needle creeps over the 180 mark the fan starts revving up. The temp will get down to just under 180 and the fan kicks off. Before my rad. recore last year it would do the same thing only in the 195 range. but after a while the fan would just stay on. The recore solved the problem of the fan staying on.

Edit: By the way Jim, I got the distributor re-curved just waiting for it to come back. ( Brian in Michigan )
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Old 04-29-2011, 08:46 PM   #26
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Well Jim, I have after market analog gauges. As soon as the needle creeps over the 180 mark the fan starts revving up. The temp will get down to just under 180 and the fan kicks off. Before my rad. recore last year it would do the same thing only in the 195 range. but after a while the fan would just stay on. The recore solved the problem of the fan staying on.

Edit: By the way Jim, I got the distributor re-curved just waiting for it to come back. ( Brian in Michigan )
Brian, Sounds like you have beat the heat into submission...Congrats.
Any idea what the ignition curve will be?
I pulled 2 degrees out of my base (back to 9*) but I'll bump it back 1* for 10* base.....
Enjoyed the way the engine performed going over to Surprise Arizona and back but feel it could stand 1 more degree of base.
Sure do enjoy the new stage 2 carb also..

Jim
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Old 04-30-2011, 10:29 AM   #27
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A thermostat is supposedly fully open at whatever temperature it is rated for. Most thermostats made now will begin to open before the rated temperature. My 180' t-stat would start to open around 165' to 170'. This increased the temperature in the radiator enough that the fan clutch would begin engagement at 170'. Fan clutchs work on the air temperature between the radiator and the clutch, and a percentage of engine speed and different cluthes are rated for different percentages. There is a good explanation of how they work on the Hayden website.

By installing a 195' t-stat the temperature when it starts to open is higher, should be 180' or so. This keeps the engine temperature closer to where it should be for emissions and mileage while not overheating.

There where, and maybe still are, t-stats of the poppet style. These do not open gradually but all at once when the rated temp. is reached.

As long as your engine temp. is good you have no problem.
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Old 04-30-2011, 11:06 AM   #28
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By installing a 195' t-stat the temperature when it starts to open is higher, should be 180' or so. This keeps the engine temperature closer to where it should be for emissions and mileage while not overheating.

There where, and maybe still are, t-stats of the poppet style. These do not open gradually but all at once when the rated temp. is reached.

As long as your engine temp. is good you have no problem.
Watching my "Robert Shaw" 180* in a pot of hot water it starts to open at 171* and is fully open at 179*, Dang thats close e'nuf for me...
No problems for Brian as his system looks like it is working fine.....
The older engines really are NOT built for the higher temps with the "Cast pistons" and thats why the stats were 180*, I don't know when or what year the engines were built to handle more heat (emissions related) but I do know but I know they are very slow to respond and only duit when the rate of failures are on the up swing....
Remember my 83 only had a 5 blade fan combined with a 4 row radiator which only had "3/8" tubes, Now a "STOCK 7 blade" with a 4 row rad is in place BUT with 1/2 inch tubes which IMHO is still marginal in our extreme summer heat....

Jim
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