Freezer coils keep freezing up.
I had a similar problem with a Maytage Side-by-SIde Model MDZ2768GEW, (purchased in 2001). Defrost not working...poor cooling in both the freezer and fridge. We opened up the back of the Freezing side and the coils were iced. This Model is auto defrost so obviously something was not working. We called a Sears repair office and they sent a guy that told us we needed to defrost the unit. Well...I wasn't home and my father-in-law didn't question it - he defrosted it! I was busy at the time and didn't pursue it until the problem naturally resurfaced a month or so later. Not wanting to haggle with Sears over their Tech's lazy incompetence (or the $100 I was out), I decided to commence troubleshooting. I'm an ex Navy nuke electrician and electrical engineer so this didn't seem to be beyond my ability.
Not having the Owners Manual, I internet searched until I found this site: www.servicematters.com/maytag_library/html/index.html. You can download your model's Service Manual and root around for other tech info their. I found the manual for mine and performed the troubleshooting for the Adaptive Defrost Control. Its fairly easy to do and you don't have to empty the entire fridge. You do have to empty the upper shelf in the fresh food (cooler) side to gain access to the controls.
--This may not be in the exact order needed but you remove the light shield by pulling down on the back corners of the cover and sliding it forward (slotted attachment - no screws). Next Remove several screws holding the fascia / radiant shield on. Then remove screws that mount the control housing to top of fridge, etc. I also removed two screws that mount the ADC to the plastic housing to get access to the ADC. Basically, remove enough screws to lower the top assembly down to get to the ADC...
--You may need to turn off the fridge now (or do it before you started the previous steps but the light helped me). If you are not using a Wattmeter, I don't think you need to pull the power cord.
--The Service Manual next says to attach a Wattmeter to the fridge (and assumedly plug it back in). Most people don't have a Wattmeter...but what I had is a clamp-on ammeter...which you can get as part of "better" multi-meters for well under $100. An ammeter is good enough if you know how to multiply voltage and current to get VA (or approximately) Watts. Any idiot can do this...I think. P(Power) = V x I x pf. What you calculate with VxI is Apparent Power (VA). You convert to "real" power (Watts) by multiplying VA x pf. You generally have to guess at pf, but 0.8 for a motor/compressor is a good approximation and 1.0 for a heater or indandescent light bulb is roughly good. Enough electrical basics...
--With Fridge plugged in, and being careful not to touch exposed connections, move the ADC control board so you can gain access to it (2 screws were removed previously to loosen it from the housing at top/back right of fresh food side). The ADC is a small printed ckt board about 3" x 3".
--Use a small insulated jumper (or insulated alligator clip) and jumper Pins labeled "L1" and "Test". These are labeled on the PC board and were the two left-most pins, side by side, on my ADC. The Manual doesn't say whether to leave the jumper on or not. I tried both ways and I believe all you need to do is momentarily jumper the two pins (but my ADC wasn't working right, which I will get to later)...so I'm a bit unclear on this part. Also - DO NOT jumper between any other pins, or you may damage the ADC, if it's not toast already. The pins are close together so you need to take some care in doing this.
--According to the Service Manual, you should read about 500-600 Watts of total power consumption if the unit is in Defrost mode. I found (referring to the electrical schematic), the main red power wire (ty-wrapped to a green/yellow wire that goes to the main lights). Power is red so it's process of elimination to find the "right" red wire. It's not that hard to figure out. I also confirmed this by playing with the door switch light and watching amps go up and down as I pressed & released the door switch. Ultimately, I measured about 2.2 Amps with the unit working normally (cooling) and 6 Amps in Defrost mode...and about 120 Vac supply. So...VoltsxAmps=VA, which equates to 720VA. I don't know what the power factor of the unit is...but with the compressor and freezer fan off, and only the defrost heater and lights on...the power factor would be close to 1.0. So my reading might have been a touch high but...what it did prove is that a) the heater works (I could feel heat off of it and I had the freezer panel removed and saw it melting ice), and b) the thermostat was working.
--I also confirmed proper thermostat operation by measuring it "open" with an ohmmeter after the defrost cycle and measuring it "closed" once it cooled down enough (book says ~ 45F thermostat opens and ~15F it closes (to allow defrost when commanded by ADC).
--What I found was that when I jumpered L1 and TEST, the Defrost didn't come on...until I manually turned the Freezer control off - and then back on again. Once I did this it started Defrosting (amps rose from about 2 to 6, compressor and freezer fan shut off and heater started heating. I repeated this twice after waiting for the unit to cool down after the defrost cycle. You can also just unplug the fridge to terminate the Defrost cycle and if the temp hasn't risen above the thermostat setpoint, you can immediately repeat jumper testing as necessary.
--The defrost heater stayed on for about 5-8 minutes and after a total of 23 minutes the compressor/fan restarted - which matched what I read somewhere - though doesn't match the ADC Instruction Manual - which I show a website for further down.
--So it appears the ADC is just not entering the Defrost cycle but does exit it properly. I believe that my problem is the ADC as I proved the heater works and the thermostat (as I mentioned earlier). Other than bad/intermittent open wiring, there's nothing else in the circuit and I believe I ruled out a bad connection by taking the thermostat connector apart several times and jostling wires up at the ADC to gain access.
According to what I can find, the replacement ADC for my unit is Part No. 12002495. One should verify the P/N for their particular model.
You can look at the Instruction Sheet here: www.servicematters.com/maytag_library/docs/16023486.pdf. It also has some info on how the ADC is supposed to work...NOTE: You should verify this P/N with someone, as I will before I order it. FYI...at Partselect.com, they show a replacement PN (their #) as PS2061226, for about $61. I've seen various prices on different sites and this was pretty reasonable. Lord knows what Maytag/Sears would charge. Maybe add a "1" to the front? ;) PartSelect also indicates different "Series" numbers for the same PS number for the ADC...not sure about which one I have so Buyer beware, make sure you resolve this before ordering -- I still have to.
Anyway, hope this is helpful to someone out there in cyberspace. I will have to confirm my P/N and then buy the ADC.
If anyone out there, esp pros, have any suggestions feel free to chime in. Except if you are the guy that told us to defrost our auto defrost fridge to "fix" the problem, for 100 smackers no less. You Sir, should be caned 100 times for being a slug. No economic stimulus for You!
May 16, 2009 |
Maytag MZD2766GES Side by Side...