Ice Maker, Pressure sensor failed, advice please

[BenG]

Hi all,
I'm looking for a bit of help with an ice machine. I have an Ice Craft ZB-15P which I took from our office when it was closed, its been used regularly but last week I was getting it ready for summer (quick clean and run a couple of ice cycles to discard) and when I switched it on, the fan started for 2 secs, stopped 2 secs, started 2 secs, then stopped and didn't come back on.
I cant remember how much the fan came on last year so proceeded to make some ice, the ice wasn't very big and the machine soon started to overheat so I switched it off.

I've done a bit of diagnostics and worked out its the pressure switch that runs the fan that has failed, if I bypass the pressure switch the fan is on constantly and the machine works well when producing ice. There is a small problem in that some of the ice doesn't drop off the freezing/ice maker prongs, but I'm wondering if this is because the fan is running constantly and the element warming cycle to eject the ice from the prongs is not getting warm enough.

The pressure sensor is marked up as Chang Heng YK-01L and the contacts are currently constantly open so the fan doesn't get powered on.

I'm wondering how I go about getting the pressure sensor replaced, I can rotate the black plastic housing and pins by apply a lot of force, but it does not seem to be a screw fitting, is it likely to be soldered on to the copper pipe?

I've searched online for the part and I cant see where to get a replacement, is there an alternative part do you think?

Schematic:
20140501_124554.jpg

Close up of pressure sensor:
20140501_100742.jpg

View of components and wiring (cables re-routed for easier viewing):
20140501_131245.jpg

Thanks in advance for any help.
Ben

[Brian_UK]

That pressure switch is brazed into the pipework. You would t recover the refrigerant, cut it out, braze in a new one and the cost of the equipment required plus the training would be vastly more than the cost of a new ice maker.

What you could do however is fit a temperature​ sensing fan controller instead. This has a sender clipped to the tubing and does not require breaking into the system.

Have a look at the 2nd item on this web page..


http://www.stockelectronics.co.uk/auto1.html

You can download the instructions also which will help explain it.

[BenG]

Thanks Brian, I though it wouldn't be an easy repair.
I think I've worked out an alternative method, that will cost about a fiver to fix it.

Using the multimeter I've seen that at the end of the ice making process the reverse solenoid is powered and the valve is activated. Looking at the copper from the solenoid, that must open the contacts on the pressure sensor which then shuts off the fan whilst the freezing element is warmed to release the ice. Once the warming process is complete, the reverse solenoid resets and that should reset the pressure sensor.

So, I think I have another way round this that will probably be cheaper than a thermal fan control. If I use a 'normally closed timed closed' relay, I can use the power to the solenoid as the trigger so when the solenoid is powered/activated, the contacts for the fan (load circuit) will be opened (fan off), then when the solenoid is powered off/deactivated, the timer starts and keeps the fan off for a further 5 seconds to ensure the ice has dropped from the freezing element before powering the fan on again.

I'll fit the relay and run it on a few cycles and see how it performs. If it works, I'm quids in!

Ben

[Brian_UK]

You can try it but the wiring diagram shows a completely story o you grasp of the operation.

The fan pressure switch is in series with the fan and powered directly, there are no other controls attached to it. The purpose of the fan is to control the high pressure refrigerant when the compressor is running. Without the fan running when the compressor is cooling then things will start to overheat and knacker the compressor. Your choice.

[BenG]

Yes the pressure switch is in line with the fan and not controlled by the logic board, the fan comes on when the unit is plugged in.
But the copper from the bottom of the reverse solenoid is also T'd off to the pressure switch (you can see this in the 3rd pic), which makes me think that when the solenoid is activated and the warming cycle begins (to allow the ice to drop off the freezing element), the pressure switch is also activated to cut the fan for a few seconds until the warming stage is complete. The warming stage takes about 5-10 seconds and during this time the solenoid is powered/activated. The freezing stage takes about 12 mins and the reverse solenoid is reset/off during this period.
Do you think my logic is right or wrong? Would you recommend that I just bypass the pressure switch completely and ensure that the fan runs constantly whilst the ice machine is powered on regardless of whether its freezing or warming the element?
The machine isn't left on for a huge amount of time, 3-4 hours at the most, in that time it produces loads of ice.
Thanks!

[Isen-Controls]

Hi Ben,
If there is a schrader valve, you can buy a new pressure switch with 1/4" female flare connect and mount it onto the schrader valve.

Mark

[Brian_UK]

The solenoid valve is the hot gas defrost to release the ice and has nothing to do with the fan control.

I am not going to continue with this, sorry, I've given an option to get the machine running properly.

[BenG]

Ok, sorry to offend. Am just trying to understand how it works.

I think my understanding of the pressure switch is wrong, I think it's probably so the fan doesn't run when the machine is idle and the compressor is not running.

Hi Mark,
Thanks for the point about the new pressure switch but braising a new one is beyond my ability.

[BenG]

Right I see now, the snippet of info in post 7 has cleared this up for me, thanks Brian.
That with the original info in post 4 has proved useful. I'll either set it up so the fan runs constantly, or use a relay from the compressor power so the fan only runs whilst the compressor it's on.