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Condenser Fan For Dash AC

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Recently purchased a 2007 CC Tribute. While driving with the dash air on, the condenser coil fan cycles every minute and runs about 15 seconds, then starts over again. It is producing cold air. The noise from the fan is annoying while sitting in the passenger seat. Wondering if its operating correctly. Never heard one cycle so often.

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Hopefully you will hear from others with the same coach.

Approved ways to turn on/off the condenser fan include using a thermostat or pressure switch. It may be that the short 15 second fan cycle is enough to take the temp/pressure from cut-in to cut-out.

Look forward to hearing from others with the same coach.

Brett

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CC stand for Country Coach- it has a Cat C9400 HP and the condenser coil is located in front under the passenger area. There is an electric fan to blow air across coil that cycles regularly (like every minute) and runs for 15 seconds.

AC works fine except the fan is loud and was wondering if the short run cycle was normal.

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Normally the fan is controlled via a relay that is attached to the power for the AC compressor clutch control. so if the AC compressor comes on then the fan also starts. So then the question is if the AC compressor is short cycling and causing the fan to cycle. An AC compressor cycling can be caused by just being low on R-134a. You might want to turn the AC on and going back and watch the compressor clutch and see if the compressor is going on an off also. If it is then it is time to get the AC serviced.

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Finally determine that the noise was a condenser fan motor about to go out. Bought a fan from Auto Zone and now is quite.

300 mile road trip this weekend and everything work fine.

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So what you are saying is that it was not cycling but a fan just making a noise? Or is it cycling and the reason you can tell it was cycling because the fan motor was bad and making noise.

Well my question to you then is it still cycling too often but you just don't hear it so you now don't care. Are you covering up the actual root of the problem?

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So what you are saying is that it was not cycling but a fan just making a noise? Or is it cycling and the reason you can tell it was cycling because the fan motor was bad and making noise.

Well my question to you then is it still cycling too often but you just don't hear it so you now don't care. Are you covering up the actual root of the problem?

Just getting back to the thread- the new fan is working fine and is so quiet I can barely hear it- from what I can tell it doesn't cycle now. This past weekend drove a 300 mile trip in 95 degree heat and everything is cooling as it should.

Thanks again for all you help.

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Robert,

The condensor fan motor was noisy so you could hear it and you stated that you could hear it going on and off and this is called cycling. Only you know this because you heard it but the question is how fast was it cycling? You said it was on for a minute and off for 15 seconds then back on again. The fact that you changed the fan stopped the noise but that fan still turns on and off at the same time as the compressor. If the cycle was short such as you described it then the AC is doing what they call short cycling and that is normally due to a low freon charge. So if you had the motor running and the AC on and went back and opened up the engine compartment you would see the center part of the compressor clutch spinning or not spinning as it cycles. Is it still short cycling? Try it and time it and see what kind of cycling is it still doing?

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"Normally the fan is controlled via a relay that is attached to the power for the AC compressor clutch control. so if the AC compressor comes on then the fan also starts."

Mike,

That may be the situation with your Monaco but is not how dash fans work. With every car, truck, and motorhome I've owned the fan is controlled by a separate fan switch on the dash -- not compressor cycling. Simply because you use the fan year round to blow air whether cooling, heating, or just getting fresh air. The last two scenarios have nothing to do with the A/C compressor. In all vehicles with a fan "OFF" position I've seen the reverse -- the A/C compressor is held off until the fan switch is activated. The rational is you don't need the A/C compressor running if you don't have air moving at the dash. When switched on, the fan runs continuously.

It is true that when using the defroster setting for heat in the winter the A/C compressor will cycle. This is to keep the A/C hose seals lubricated during the winter months when the A/C system generally is not used. But the dash fan does not cycle on and off.

A fan motor with a bad bearing or other shaft alignment issue will make noise and can have excess friction that will open the motor's over temp switch when the fan overheats. After it cools, the switch closes and the process of intermittent air and noise begins again.

The A/C system's low freon pressure switch will inhibit the compressor clutch from working at all until the system is properly charged.

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Mike

The compressor does not short cycle and I had the freon level checked and it is OK. Believe the condenser fan was short cycling because the motor was about to go out. Replaced and all is well.

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Chuck, Mike and rhuffhines;

I believe Chuck is talking about a DIFFERENT fan than are Mike and rhuffhines.

With an A/C system, you have two different fans. The evaporator fan-- the one in the dash that you feel coming out the vents and runs for heat, defrost, etc as well as A/C.

The other fan is the condenser fan. Depending on location of the condenser, it may have a separate fan or it may use the main engine fan or a combination. It does cycle. The cycling can be triggered by compressor on, freon/coolant pressure etc.

BTW, your stick home has two fans as well, with the condenser outside and the evaporator inside the home.

Brett

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Brett, thanks but I know exactly what fan I am talking about :lol: . rhuffhines stated that it was the condensor fan that was cycling. So my analysis of the problem was based on the condensor fan. I agree on a DP the condensor fan is usually located on the condensor coils unit which is under the front of the MH. Chuck you are talking about the evaporator fan which is the heater and AC fan located inside the dash unit that blows air in your face. I am sticking with my story. ;)

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From the original post

"...the condenser coil is located in front under the passenger area..." and the fact most DP condenser fans are not in the front of the coach (like mine is) led my mind immediately to what is generally a complaint by the driver -- a noisy evaporator (dash) fan. My error! And it just gets worse with age.

The information on the motor is correct. I have seen it many times with small electric motors to those of many horsepower. Also, every A/C system I have seen has a low pressure switch that opens the circuit to the compressor clutch. Unless you have a defective low pressure switch, or none at all, I fail to see how you manifest "short cycling" of the clutch. That said, being true for the Ford and GM products I've worked on. But I have to admit I've seen many shortcuts in the RV manufacturing industry and I can see how the absence of a low pressure switch might cause unpredictable results.

But as rhuffhines said,

The compressor does not short cycle and I had the freon level checked and it is OK. Believe the condenser fan was short cycling because the motor was about to go out. Replaced and all is well.

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We bought a 2003 Fleetwood Southwind in April and took it from New Jersey to Florida and experienced the fan clutch cycling when the AC was on and going uphill. It was extremely noisy and never owning a motorhome before I thought this was normal. When we returned home I had it look at and of course the noise couldn't be duplicated here because we're so flat here. We went to the west coast and back in July, 2011 and the temps were in the 90's and up so the fan clutch was constantly running or should I say screaming. When it came on it sounded like a jet taking off.

There was no way I was going to put up with this so I bit the bullet and had the fan clutch replaced. I also bought a sound/heat dampening material and placed it around the engine. We went back to Florida in October and needed the AC and when the fan clutch came on I could barely hear it. I opened the window just to see if the sound dampening material was just keeping the sound out, but I couldn't hear it.

Replacing the fan clutch did the trick for us and that was a shot in the dark since there was no definitive proof that it wasn't working properly.

I hope this helps anyone that is experiencing the loud fan clutch noise.

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On a front engine motor home the loud noise is made by the engine mounted radiator cooling fan when the fan is in full engagement to properly cool the antifreeze mixture flowing thru the radiator when it exceeds a preset temperature. When the temperature is reduced by the large volume of air the fan will partially disengage and operate at a much slower quieter speed until the temperature again raises and the cycle repeats. ( crud on outside of radiator, hot weather, large hills, air conditioning==== more loud fan noise )

It is your responsibility to see that all equipment mounted ahead of the engine cooling fan is kept free of all crud that blocks air flow through the fins of both sides of the radiator, air conditioning, power steering, etc.

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9 hours ago, RavenWarrior said:

Does anyone know where the compressor clutch relay switch is located on a Monaco Knight 03 with a Cummins 315 ISC?

Welcome to the forum. I don't have a clue.:) But someone with more knowledge on that coach will be along. You might try asking on this forum too. 

http://www.irv2.com/forums/f115/

or

http://www.topix.com/forum/com/mnc

Bill

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On 9/17/2016 at 10:51 AM, RavenWarrior said:

Does anyone know where the compressor clutch relay switch is located on a Monaco Knight 03 with a Cummins 315 ISC?

The high pressure side switch is located real close to the evaporator coil and the low pressure switch is close to the condenser coil . So it you have a side mounted radiator - the evaporator is often located in the rear.

You are asking about a switch and I need to ask it the question relates to the AC compressor not starting? The compressor will not run if the charge is too low and will quit if the high side pressure goes to high.

Rich.

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