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.

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.

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.

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.

Surge protector for the entire boat.

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.

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-...1523107904&sr=8-5&keywords=2+pin+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.

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?

Dougcole said:

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?

Click to expand...

Are the wires black, yellow and red? if so the yellow wire is a signal or tachometric wire

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.

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?

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.

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.

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?

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.

Dougcole said:

The fan is made by costech. it is labeled 12V 0.24A.

Click to expand...

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 it’s 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
Mike

Welcome aboard. I have a Vitrifugo refer in my boat. It didn’t 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.

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

If you look at Digikey or Mouser, you will find they have hundreds of fans of all sizes, amperages, and voltages.

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.

New boat season started. Today I installed new stock 0.24 A Costech fan from another compressor unit.

It works like a breeze (!) and verifies the other 0.74 A fan was causing the overload in my case.

BR
// Mike

Do you send the control boards and fans back to Isotherm for diagnoses?

OldDan1943 said:

Do you send the control boards and fans back to Isotherm for diagnoses?

Click to expand...

Hi, no that I haven't done. Do you recommend doing it? Will they charge me anything? I certainly wouldn't mind having a spare working controller if it's a simple fix.


For the old fan I would not send it in to Isotherm, since it was obviously placed there by a previous owner of the boat. They had also put some foam vibration dampening material around the fan which reveals the DIY job


Also the previous owner probably had no idea of correct fan amperages.



Thanks /Mike

rhapsody34 said:

Hi, no that I haven't done. Do you recommend doing it? Will they charge me anything? I certainly wouldn't mind having a spare working controller if it's a simple fix.


For the old fan I would not send it in to Isotherm, since it was obviously placed there by a previous owner of the boat. They had also put some foam vibration dampening material around the fan which reveals the DIY job


Also the previous owner probably had no idea of correct fan amperages.



Thanks /Mike

Click to expand...

Mike, I am surprised Isotherm didn’t ask you to send the controller back to them, to trouble shoot.

OldDan1943 said:

Mike, I am surprised Isotherm didn’t ask you to send the controller back to them, to trouble shoot.

Click to expand...

Actually, nothing against them because I never contacted them
I just bought a controller off eBay and replaced it. But of course a good plan is to have them look at the old one.

rhapsody34 said:

Actually, nothing against them because I never contacted them
I just bought a controller off eBay and replaced it. But of course a good plan is to have them look at the old one.

Click to expand...

Isotherm puts out a very good and reliable product.
And money you might have saved by buying on eBay goes out the window when you bought the 2nd replacement board.

You could be the one buying defective boards off of eBay.
I would call Isotherm tell them what you want to do and why. Send the the controller for trouble shooting. I suspect they will give you specific instructions and perhaps they have a fan they can ship you with the new controller.

My dad used to tell me, “Why is it we never have time to do it right the first time but always have time to do it again.” This may be one of those times.

I totally agree on your point here - and to clarify my case in sourcing parts - my purchase was not some eBay knockoff control unit. I came across a brand new original complete BD35F compressor assembly at a good price. This is the "donor" for the control unit and fan currently operating in my boat. Another plus with this purchase is I now have a spare compressor for should my current unit fail.

Hi again all,
Today, after a few weeks of operation, the newly installed stock Costech 0.24 A fan has failed.

Measuring on the fan when unplugged shows open circuit across it. Positive and negative leads have good connection from terminal to fan pcb.

I will buy a ball bearing PC chassis fan of similar amperage and size to make it through my sailing vacation, but will later send in the original to Isotherm.

From the stories in this thread it appears Isotherm had a strike of bad luck when sourcing the Costech fans.

Will keep you posted with more info.

BR / Mike

I replaced a stock Costech fan (model D12A04LWS ZC0, 120mm x 25mm) in the BD 35 compressor in my Vitrifrigo when it was brand new, just because it was louder than I like.

I went with a Noctua NF-A12x25. The quality difference is immediately apparent even when just handling the fan. Heavier, better rubbery insulation around attachments, quieter. I went with the NF-A variant because my fan pulls through a "radiator"on my compressor and the design of the "A" is better for that. If the fan is blowing "free" air around a compartment (some compressors look like they do that instead) then the NF-F variant is supposed to be better.

I attached the new one with small zip ties rather than the original screws. Reason is on mine the screws were very hard to get in and out, and I was doing a trial of the new fan. Not sure there is any good reason to put the screws back, but the pattern is the same if desired.

Frosty

Hi Frosty,
Thanks for the info. The Noctua looks really good and they even stock it in my local computer store franchise.

I assume you crimped couple of flat terminals in place of the PC motherboard fan connector? And just forget about any signal / tacho “3rd” wire?

All the best / M