Thursday, June 18, 2009

All That Jazz, or, How I Became Qualified to Fix A Refrigerator





Herewith is presented a cautionary tale for folks who own an Amana ABB1927DEQ refrigerator with the freezer down below.

The problem began when the freezer got iced up and the refrigerator compartment stopped cooling. I figured that the freezer door had inadvertently been left open. It was in need of vacuuming all the previous owner's collection of cat fur out of the vents and off the heat exchanger coils and defrosting for a day.

A week later, we were back with the same problem and this time I figured I'd have to get it right or face the prospect of buying a new fridge.

The conventional wisdom suggested that the fault lay in the auto defrost system, in particular the timer.

Let me explain.

When frost free refrigerators came on the market the defrost cycle was controlled by a mechanical clockwork timer, and that's about how things went for 30 years. Then we entered the brave new world of adaptive defrosting, which incorporated a small circuit board with a proprietary integrated circuit made of unobtainium. The idea is that the refrigerator learns your door opening habits and adjusts the defrosting cycle accordingly.

There is, in addition to the control mechanism (timer or Jazz board) a limiting thermostat (pictured) that ends the defrost cycle if the temperature rises above a set point, and a heating coil that wraps around underneath the cooling coils. Any water thus generated during this cycle is drained off to a small pan for evaporation.

I don't know about you, but I'm not real happy having something that spends its days in the kitchen ruminating on my habits. What's it going to do? Tattle on me to some group of militant vegan energy cops in earth shoes if I slide in for a midnight snack?

Well, nevermind.

In order to do this you have to gain access through the freezer compartment. Removing the baskets, the door, and the slides is simple and easy to do with a small (1/4 inch I think) nut driver. Once the rear panel is exposed it can be removed. Remember everything's plastic and it snaps apart and together, except for stuff that is held together with sheet metal screws.

It also helps to have a schematic diagram handy. I found this one on a website that sells refrigerator parts.

Once the back panel of the freezer compartment is exposed you will see the defrost terminator pictured, and the heater element which is a black insulated thingy that goes around the lower parts of the coils.

With a multimeter you can check the heater from one end to the other. If the resistance is infinite, the heater element is broken and needs to be replaced.

At the same time you can test the defrost terminator by connecting a multimeter to it and then immersing it in a mug full of ice water and salt. If the terminator goes from infinite resistance at room temperature to about 55 ohms it's working properly. In my case the resistance never changed, so the terminator was bad-although it would have let the defroster run all the time, so that wasn't why this fridge iced up.

If you've eliminated the defrost terminator and the heater coil as the sources of your problem you know what's coming because either the timer is bad or the Jazz board has failed.

Opening the upper door there's a panel that houses the temperature selectors and the Jazz board. Popping it open (all plastic, snaps together) exposes the board which is actually two boards permanetly held together with a flat cable. It's easily changed by removing the connectors (white) and opening the plastic tabs.

A new board cost me $83 plus tax and a defrost terminator was about an additional $25 at Allparts in Des Moines.

You can install the defrost terminator thermostat as I did by cutting the wires and using crimped on butt connectors. Tie everything up out of the way with some tie wraps.

Once the Jazz board is installed and the rest of the refrigerator is reassembled you can power it up.

You have to program the Jazz board, and an instruction sheet should be provided with the replacement part. I've reproduced it for you.

Parenthetically, some engineer at the Maytag works where this thing was made must have had a few laughs naming it a Jazz board and using a proprietary integrated circuit that can't be found or duplicated.

Jazz indeed. I hope that person enjoyed losing their job when Maytag closed its doors forever.

Karma is truly a bitch, as they say.

It's been a week or so, and it hasn't iced up again so I'm declaring this one fixed for now.

3 Comments:

At 1:26 AM, Anonymous Jim Lang said...

I stumbled across your old post while researching an icing problem with a Kenmore refrigerator with a bottom freezer. I found it well written and helpful -- but inaccurate in one regard. If you test your defrost thermostat by plunging it in salty ice water and the resistance never drops, not only is the thermostat bad, it will prevent the defrost heater from ever energizing and thus prevent defrosting. When the thermostat is cold -- as in caked with ice -- it is supposed to act as a closed switch that allows current to pass to the defrost heater. Then when the coils heat up to a temperature well above freezing, the thermostat is supposed to open and act as an open switch that cuts off the flow of current to the defrost heater and effectively end the defrost action. Thus a defrost thermostat that fails to conduct at a sub-freezing temperature will prevent an effective defrost cycle and is a very common cause of failure to defrost in these Kenmore / Amana / Maytag / Whirlpool bottom freezer refrigerators. A defective heater, a defective defrost thermostat or a defective jazz board -- each can independently cause a failure to defrost.

 
At 5:43 AM, Blogger Robert Luedeman, attorney at law said...

It was an adventure worth memorializing even though I missed the mark on the consequences of a topping thermostat failure. It's been running like clockwork ever since but the deal with the Jazz integrated circuit was a transparent attempt by the people who designed it-Maytag- to sell more $80 circuit boards instead of fifty cent integrated circuits. That kind of thinking is, in a word, chicken shit, and for that reason, at least a few people of the ancien regime in Newton got exactly what was coming to them.

 
At 3:18 PM, Blogger Robert Luedeman, attorney at law said...

And if memory serves me correctly I jumped the thermostat and nothing happened either way.

 

Post a Comment

<< Home