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Old 04-02-2018, 07:19 PM   #1
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Isotherm Fridge fan failing

Last year I installed an Isotherm drop in fridge/freezer in the summer kitchen on our FB. It worked great for a couple of months, then when we were in the Bahamas the compressor fan stopped working. I attributed it to a power surge, as the marina (the entire island actually) was having real problem with surges.

The compressor still worked, and the unit still cooled (though not as well) but the fan wouldn't come on.

So I called Isotherm when we got back and they were nice enough to send us a new fan, saying the fridge is under warranty. I installed the new fan and it was great for about a month, then it happened again. This time Isotherm sent me an entire control module and a new fan. I put them in, two months pass, and same result, no fan. I'm still under warranty but would like to repair the unit as I had a custom stainless lip fabricated for it to allow installation.

I was concerned about voltage drop, but Isotherm said that is not what it is. I was also worried I didn't have enough vents (3 holes, each about 3.5 inches in diameter) but that is more than the manual calls for and the tech said I was fine there too.

I'm stumped. Any ideas?

I'm considering hard wiring the new fan they send me directly to the DC supply. It would run almost all the time (I'd put a switch on it) but I'm ok with that.
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Old 04-02-2018, 07:41 PM   #2
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What voltage are you running the fridge on, 12VDC or 24VDC?
Is the fan rated for the voltage the fridge operates on?
Check that first. If the compressor is a Danfoss it will run on either 12 or 24VDC but if the fan is not rated for the voltage it may not be happy even though it runs. I would expect this not to be the case but find out for sure. Even the fridge guys may assume the fan is rated for the correct voltage.



So the fridge continues to work after the fan croaks?
Goofy fans?
What are the fans?
Photo of the fan, mfgr., model and voltage on label?
Checked the voltage the fan actually receives when running?

Seems odd alright that it keeps doing this.

It should not be needed to direct wire the fan with a switch. Use a small 12V relay tied to the control output so the relay then turns the fan on/off in synch with the control.
If you do that though use a small diode on the relay control leads as that relay coil can produce a surprisingly high back voltage when de energized which may damage the control.
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Old 04-02-2018, 09:12 PM   #3
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Thanks for the reply C Letric.

The fridge is a 12VDC/AC model,the Isotherm BI-53, and I'm running it on 12V, there is no 24V on my boat.

Here's a link to the unit, though mine is an AC/DC model. https://www.defender.com/product.jsp?id=1770770

I'll have to pull the fan to get the wattage off of it. I can check the voltage on the fan next time I'm down at the boat.
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Old 04-02-2018, 11:24 PM   #4
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Have you checked the size of wiring that is going to the refer? Make sure that you are getting good voltage to the whole unit. I would put a meter on it when it is under load with your normal conditions and see what the actual voltage is.
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Old 04-03-2018, 05:37 AM   #5
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Surge protector for the entire boat.
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Old 04-03-2018, 06:24 AM   #6
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I was pretty concerned about voltage drop on installation, as there is not much info from the company about specs. I think I got that OK, as I went one size bigger than the formula required. The wire is 6 gauge, I think the round trip run is about 30 feet, though I can't remember for sure. The fan has been failing while it is on AC power, so wouldn't that negate voltage drop?

There have been no more surges, that was a one time thing while we were in a transient slip.
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Old 04-07-2018, 08:48 AM   #7
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OK, not sure this will provide the needed clues here, but I got a replacement control module and fan from indel webasto yesterday. The fan is made by costech. it is labeled 12V 0.24A. I can never seem to post pics on TF, but here is a link to a fan on Amazon that seem exactly like it, despite being from another manufacturer. https://www.amazon.com/Saim-Sleeve-B...n+computer+fan

They are so close and so cheap that I ordered a couple of them just so I could have spares. I'm also considering adding an auxiliary fan to my galley fridge, so I may use one for that.

The control module is labeled 12/24 V DC. 100-240 V AC. 50-60 Hz. So not much help there.
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Old 04-07-2018, 08:52 AM   #8
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I also found on amazon a four pack of fans with the exact same dimensions, but they draw .16 instead of .24 amps. They also have a 3 wire hook up instead of 2 wires.

I'm tempted to buy a pack.

Question, will they work despite being lower amp draw? Do you think the lower draw means they run slower, move less air?

Do you think the third wire is for some sort of temp sensor or speed control from a mother board? Will I just be able to connect two of the wires (+ and -) in my application and have it work?
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Old 04-07-2018, 09:08 AM   #9
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Quote:
Originally Posted by Dougcole View Post
I also found on amazon a four pack of fans with the exact same dimensions, but they draw .16 instead of .24 amps. They also have a 3 wire hook up instead of 2 wires.

I'm tempted to buy a pack.

Question, will they work despite being lower amp draw? Do you think the lower draw means they run slower, move less air?

Do you think the third wire is for some sort of temp sensor or speed control from a mother board? Will I just be able to connect two of the wires (+ and -) in my application and have it work?
Are the wires black, yellow and red? if so the yellow wire is a signal or tachometric wire
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Old 04-07-2018, 09:08 AM   #10
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A lesson learned the hard way. Need 1 buy 2. Always buy at least one more than you currently need. If you go back to the same store for a replacement, they may not carry them anymore.
Of course, when it come to fuel filters, buy at least 6 at a time, for each application.
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Old 04-07-2018, 10:41 AM   #11
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From the pic on Amazon it appears that all three wires are black. But since they are 12V, one of them should be a control wire of some sort, right?
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Old 04-07-2018, 10:51 PM   #12
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The extra wire could also be a 2 speed run setup. If it were an AC fan it could be a ground.
You may find when you get them that there are markings or different colours or stripes to designate wire function. Examine closely. Look at the label and it should indicate the function.

I'm just going to make a comment. These are sleeve bearing units. I suggest for the future purchase ball bearing equipped units. They will run quietly for far longer than the sleeve bearing units. Bit more money but they are better.

I have lots of both and I have to open the sleeve units every season and re-oil them. I use a synthetic, Royal Purple. The previous oil actually lasted better but was so thick it took 1/2 hour for it to get up to speed, but it lasted. Not hard, just a pain. There is no felt oil reservoir in these things so when the oil starts to dry out it starts to rattle and after some time they quit.
The ball bearing equipped units have run the same time and they are still dead quiet.

Re current: Less current draw generally means a less powerfull fan so less airflow. Design will have an effect but current is a good indicator.
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Old 04-07-2018, 11:03 PM   #13
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Sorry, another comment.
Did Isotherm give any indication of why these things are croaking?
I've used many of them over the years and have found them highly reliable. Something goofy is going on. Maybe they got a bad batch of maybe they went too cheap.

Is the old fan a sleeve bearing unit? I ask since from my own experience they do not have the life of the ball bearing units especially if made by a decent co. Re oiling them is not good for your buried fridge if that is what is going on.

I see the unit is powered by a Danfoss BD50 compressor and those things have an outstanding reputation. Of course not foolproof but very, very good so it's odd about the fans.
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Old 04-08-2018, 09:25 AM   #14
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So far Isotherm has not been able to come up with a solution for why the fans are failing. I'll be down at the boat next week when I'll change out the control module for the second time and the fan for the third time. I'm going to return the old module and fan to them for testing.

They have said that if this fix doesn't work that they will need the entire unit returned to them.

I'm also going to cut another vent in the cabinet and go up one size on the wire. I don't really think either of these things is the issue, but they are easy to do and I'd like to eliminate them as even possible causes.

The compressor is still working, the box cools, just not very efficiently.

I don't know if the old fan is a sleeve bearing unit. How can I tell?
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Old 04-10-2018, 08:58 AM   #15
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Usually the label , the specs. or the seller can tell you.
If it does not say then assume it is a sleeve bearing unit.
Most of the ones that are ball bearing say so either on the unit, the box or in the specs.
The ball bearing units are usually somewhat more money.
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Old 07-16-2019, 09:33 AM   #16
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Quote:
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The fan is made by costech. it is labeled 12V 0.24A.
Hi all,
I have the Isotherm ASU unit in my boat, which has the BD35F compressor unit like many other models. Some googling led me right to this thread. After changing a faulty control unit (compressor would not start), the fridge was up and running again but suddenly a fan problem happened: the compressor seemed to struggle more than usual and a quick look revealed that the fan was not spinning at all. I removed and tried to brush off the wire terminals as I thought it might be some oxidation there, and when I re-connected after some minutes, voila, fan spins up!

But... only for half a day or so. Now itís stopped again. Comparing above stated amperage with my unit made my eyebrows raise: my fan is 12V 0.74A! Three times the amperage of your units... This seems to make no sense - unless the previous boat owner has put in a wrongly speced 120mm fan there. I suspect now that my fan is OK, but the control unit may trip the fan output due to overload.

Anyone else seen a 0.74A fan installed in these units?

Best Regards
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Old 07-16-2019, 10:46 AM   #17
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Welcome aboard. I have a Vitrifugo refer in my boat. It didnít have a fan installed so I installed one. The manual said it could support a .5 amp fan. I put a .05 amp fan in and it made the refer work much better along with 2 vents, one high and one low. .74 amps is a huge draw. I woul look for a much smaller draw fan.
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Old 07-16-2019, 11:08 AM   #18
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Thanks for your input, Comodave. I will definitely try to source a lower amperage fan like an 0.24 A one or similar. Will get back with results!

BR//Mike
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Old 07-16-2019, 11:12 PM   #19
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If you look at Digikey or Mouser, you will find they have hundreds of fans of all sizes, amperages, and voltages.
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Old 07-17-2019, 10:07 AM   #20
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What I did when I had bus heaters, I used a 24 volt (ball bearing) fan which ran at half speed and therefore was much quieter.

Those fans are intended for continuous duty so it is the fridge’s problem. Keep after the manufacturer.
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