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Fridge Fan - does it have to cycle?
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Summers420us
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PostPosted: Mon Aug 09, 2010 8:54 am    Post subject: Fridge Fan - does it have to cycle? Reply with quote

I replaced the fan on the back of my fridge with a compter fan. It is much quieter than the original and I can feel the difference in the air ciculation around the cooling fins.

But... With fridge in full operation the fan comes on for 15 seconds or so, then turns off for 15 seconds or so and then repeats this cycle.

Even though the fan is not very noisy, this cycling drives me a bit nuts when I am trying to sleep.

Is this fast cycle normal behavior?

Does the fridge work better with the cooling fins at a certain temp that requires the cycling of the fan, or can I just wire in a bypass switch and run the fan constant?
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Summers420us
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PostPosted: Mon Aug 09, 2010 9:37 am    Post subject: Reply with quote

ragnarhairybreeks replied to me and said:

Quote:
<I experienced same behaviour with muffin fan replacement. They don't seem to work as well as other fans in this application. One thing to check is the thermoswithc on fins, make sure bracket is holding it tight>


So, I will go back in and double check the connection of the thermoswitch... but that still leaves me curious:
How long is a normal fan on/fan off cycle?
Is it possible to just leave the fan on all the time?
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ragnarhairybreeks
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PostPosted: Mon Aug 09, 2010 9:47 am    Post subject: Reply with quote

I don't see a problem with keeping fan on all the time, well apart from battery drain. You can't really "over cool" the fins Smile

But, what I found to be the best mod, is to use the external water hoop up access port (not the water tank fill port) as a vent. Gut the plumbing and add muffin fan there. You can prop up the flap and then turn on that fan and it draws out hot air from behind fridge. Can wire in parallel to fridge fan or have on its own switch.

alistair
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PostPosted: Mon Aug 09, 2010 11:24 am    Post subject: Reply with quote

It could be the muffin fan is cooling the thermostat enough to shut it off, when it really has not cooled the fins. Make sure the thermostat is getting good contact...I put some thermal grease between the thermostat and the cooling fin.
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PostPosted: Mon Aug 09, 2010 11:39 am    Post subject: Reply with quote

ragnarhairybreeks wrote:

But, what I found to be the best mod, is to use the external water hoop up access port (not the water tank fill port) as a vent. Gut the plumbing and add muffin fan there. You can prop up the flap and then turn on that fan and it draws out hot air from behind fridge. Can wire in parallel to fridge fan or have on its own switch.

alistair


Alistair, do you have a picture of this mod? On our last trip, towards the end, I noticed the stock fan was starting to make noise. I tried to see if I could quiet it, but could not really get to it even with the inside vent off. I decided to pull off the city water housing to look in. Within a minute of removing the housing, the fan quit running. I reinstalled the housing and waited for the fan to come on. I repeated the above as a test. Within a minute, the fan quit again. It got me to thinking, a better vent might be an improvement. I thought about utilizing the housing as you describe, but did not want to add a rain leak. The member spitsnover I believe came up with a very improved system that utilized old fridge parts and added a second modified Fridge vent. He has some other interesting fridge mods. http://www.griffco.ca/interest/vw/vwfridgevent.htm
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Vanagon Nut
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PostPosted: Mon Aug 09, 2010 11:51 am    Post subject: Reply with quote

ragnarhairybreeks wrote:
I don't see a problem with keeping fan on all the time, well apart from battery drain. You can't really "over cool" the fins Smile

But, what I found to be the best mod, is to use the external water hoop up access port (not the water tank fill port) as a vent. Gut the plumbing and add muffin fan there. You can prop up the flap and then turn on that fan and it draws out hot air from behind fridge. Can wire in parallel to fridge fan or have on its own switch.

alistair


When the ambient temp gets high enough, and interior temp gets even higher (picture your Westy, all closed up, in a sunlight parking lot on a 100F day), the fridge works a lot harder. This creates more heat at rear of fridge. In that case the rear fan would likely stay on the whole time.

As per Alistairs comments, I installed a City Water fan with a switch. I also installed a separate "bypass" switch for the stock rear fan. Both fans can be powered by aux. battery or shore power via a wall wart and the stock rear fan can still be turned on via the stock thermo thingy. City fan is switched on all the time in hot weather. Both get switched on if it's really hot out. They help a lot. Mine are powered by an aux. battery.

Neil.
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Summers420us
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PostPosted: Mon Aug 09, 2010 11:59 am    Post subject: Reply with quote

Would love to see pics of the city water to fan mod...

Curious.. what's "wall wart"? Confused

Still though can anyone tell me what is considered a normal cycle. Let's say the ambient air is 85F.
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ragnarhairybreeks
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PostPosted: Mon Aug 09, 2010 1:25 pm    Post subject: Reply with quote

I didn't notice a leak from the wall fan mod in my case. I can understand the worry though. I relied on the stock flap on the city water port to do the sealing, maybe gasket that too? Hold on, I now recall, I had a square of ensolite in there too as a full gasket, and I used it to prop up lid when in use.

boy my memory comes and goes.

spits&rover's mod quite nice. Neil's mod is here:http://sites.google.com/site/tubaneil2/citywaterfanmod

No pics of my mod, but its pretty simple, the muffin fan I had on hand was perfect fit onto plastic in city water port... attached from backside/interior

alistair

PS your 2 posts are intertwined now, sorry about that
PPS I can't give you exact duty cycle data, just that the muffin fan alone came on more than the stock fan, and I noticed it repeatedly cycling. City water vent reduced this a lot.
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Vanagon Nut
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PostPosted: Mon Aug 09, 2010 1:34 pm    Post subject: Reply with quote

Summers420us wrote:
Would love to see pics of the city water to fan mod...

Curious.. what's "wall wart"? Confused

Still though can anyone tell me what is considered a normal cycle. Let's say the ambient air is 85F.


Wall wart = AC adaptor. Sorry for the slang.

I'd suggest there's too many variables for anyone to give a concrete answer: age of motor (efficiency), wiring, thermo switch etc.

IMO, if it comes on when interior hot, then goes off (eventually) when van opened up, then it's doing its job.

I just measured 2 spare Dometic rear fans. They each draw ~ 0.27 amps. That's not much. Smile

City water fan pics

http://picasaweb.google.com/musomuso/DometicPics?authkey=Gv1sRgCOn8wqShjI200QE#5371078715234588706

I cut out the middle of the hook up and epoxied in a piece from a freezer tray. It fit and is somewhat robust. Looks like ass, but works fine. Needs a mesh of some sort to keep bugs etc out. Fan was installed using blind bits of metal. Can't recall those details right now though.


Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.

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Vanagon Nut
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PostPosted: Mon Aug 09, 2010 1:37 pm    Post subject: Reply with quote

ragnarhairybreeks wrote:
....

spits&rover's mod quite nice. Neil's mod is here:http://sites.google.com/site/tubaneil2/citywaterfanmod

No pics of my mod, but its pretty simple, the muffin fan I had on hand was perfect fit onto plastic in city water port... attached from backside/interior



Oops. Didn't see your link Alistair. Wink

Summers420us: computer case fans vary in specs. You may find a high CFM rated fan that while noisy, may have a relatively low amp draw. The trade off being the higher noise level.... I think. Regardless, easy to find one that draws less than 0.5 amps.
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spitsnrovers
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PostPosted: Mon Aug 09, 2010 2:16 pm    Post subject: Reply with quote

More fridge cooling info here
www.griffco.ca/interest
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PostPosted: Mon Aug 09, 2010 2:41 pm    Post subject: Reply with quote

Ok, I pulled the city water hatch off the old westy...

its a small fan all right, but it does move the air out of behind the fridge. Bit of foam keeps out moisture when hatch closed. Sorry about glare in pics, but you might be able to make out model number on fan.

alistair


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Summers420us
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PostPosted: Tue Aug 10, 2010 4:56 am    Post subject: Reply with quote

That is a great mod and will be added to my list!
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PostPosted: Tue Aug 10, 2010 8:06 am    Post subject: Re: Fridge Fan - does it have to cycle? Reply with quote

Summers420us wrote:
I replaced the fan on the back of my fridge with a compter fan. It is much quieter than the original and I can feel the difference in the air ciculation around the cooling fins.


Which way is your fan blowing? Is it directed at the fins and blowing air directly on them or is it pulling air across them? I imagine that you'll get better control if you're using the fan to pull air across the fins and blow heat out of the cabinet. It may help your short cycle problem.
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Summers420us
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PostPosted: Tue Aug 10, 2010 1:01 pm    Post subject: Reply with quote

same as OEM.... pushing air across fins not pulling away from fins.
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PostPosted: Tue Aug 10, 2010 2:11 pm    Post subject: Reply with quote

Yes othe OEM pushes air up over the fins.

if you install a 'city water' or other vent on the side fo the van, it must suck the air out of the van.

The hot air pulled out through the vent works fine. Cooler air is always at the lower intake under the fridge.

I've measured the temp coming out the vent installed on mine at 39 deg celsius!
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PostPosted: Thu Sep 08, 2011 7:38 pm    Post subject: Reply with quote

Bump for an old thread...anyone know what the temp should be for thermalcouple to kick the fan on? I'm getting a signal to it but not out...fins are at about 104-106deg
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ragnarhairybreeks
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PostPosted: Thu Sep 08, 2011 7:49 pm    Post subject: Reply with quote

Can't help you with the temp at which the TC operates, but I think I will be looking into it as I want to improve the back fin cooling some more. I mentioned back at the beginning of this thread that my muffin fan cycles on and off to frequently for my liking and the explanation that the fan is cooling the TC enough for it to shut the fan off, but not enough to adequately cool the fins seems like a good one. So I will be pulling the fridge in the next day or so to double check the TC and how well it is making contact with the fins and also to see if I can put in another fan.

I don't have a water port in the van that the fridge is now in, and I don't want to cut a hole in the van, so I will be revisiting old ideas on how to improve fin cooling.

alistair
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PostPosted: Fri Sep 09, 2011 4:11 am    Post subject: Reply with quote

Firing mine up a week ago for the 1st time is my training on this type frig. Any one experiment with flame size?? Would that increase cooling if more cooling to fins is added at same time? I plugged mine to AC earlier last yr to see if it worked on that mode and left overnite, seemed to get pretty cold inside, didn't have an inside therm to measure temp but did seem colder on the ac.
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PostPosted: Fri Sep 09, 2011 6:49 am    Post subject: Reply with quote

Well, plugged in all night and here are the temps

81 inside the westy
41 inside the bottom of fridge w/frozen solid ice cubes on top...frost on the fins. my house fridge was only 43deg...so good enough I suppose.

I don't think i'll get any better then that other then doing the citywater mod.

no time for that right now though, so this should have to do.


I did buy an inside fridge fan (battery operated) that kept for a nice even temp in my fridge.
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