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-   -   Blowing thermal fuses (http://forum.appliancepartspros.com/dishwasher-repair/460974-blowing-thermal-fuses.html)

Gilbert K 04-06-2012 11:34 AM

Blowing thermal fuses
 
Our Kitchen Aid dishwasher was blowing thermal fuses and when I checked the heater element and I had ohm readings of 57 to 95. The wiring diagram indicated a reading of 35. I order a replacement, installed it and everything worked fine for 2 weeks before it started blowing thermal fuses. Using my multimeter, the readings were again up to over 50 on my meter.

I called and was shipped a replacement element. Before I installed I tested and readings of 35 to 117 in repeated tests. Is this correct or is there something else I need to look for.

I greatly appreciate your thougths and help.

Simon / APP Team 04-06-2012 12:59 PM

Hi.

If your dishwasher has stainless steel tub you have to use

heater kit which includes control board.

The kit Part number: AP3841139

Part number: AP3841139


Also make sure you are using correct fuse kit and you are installing new wires.

The fuse kit Part number: AP3178588

Part number: AP3178588


The resistance of the heater is 10-35ohms.

Check the thermistor 48-53 K ohms at 77*F between P2-2 and P7 at the control board.

The thermistor Part number: AP3039201

Part number: AP3039201


The hi-limit thermostat may not be opening.

The hi-limit Part number: AP3010530

Part number: AP3010530


Thank you. Post the results.

Simon.

Gilbert K 04-07-2012 03:04 PM

Blowing termal follow up
 
Simon

I have the stainless tub and two service appointments to replace the fuse with the new harness. Since I have replaced the fuse setup several times before I found the thermal fuse and now I just replace the fuse when necessary. I tested between the P2-2 (yellow) and P7 (white) but the meter did not move.

Does that indicate that the Thermistor needs to be replaced?

Does the variance in the heater element indicate a problem there or is that normal?

Thanks

Simon / APP Team 04-09-2012 05:26 PM

Hi.

The thermistor resistance is 48 - 53 Thousand ohms. Set you meter to max scale.

You haven't answer the question: Did you replace the heater and the control board?

Please reply.

Simon.

Gilbert K 04-09-2012 06:43 PM

Blowing thermal fuses
 
Simon

Yes I did replaced both the heating element and control board. I noticed that with the new board, the machine starts the cycle after about 3 sec it stops and continues to at water.

When I placed the digital meter on the 2 wires the meter stayed at 1. I am traveling for the next 4 days and will be able to test again on Friday.

Gilbert K 04-18-2012 07:55 PM

Thermistor
 
Simon

I tried to us my ohm meter on the P2-2 (yellow) and P7 (white) wires but the reading did not change. Does this mean that thermistor needs to be replaced? Where is the thermistor in the dishwasher so I can test directly.

Simon / APP Team 04-18-2012 09:28 PM

Hi.

If you look under on the right side of the wash pump housing approximately 3 o'clock. 1/4 turn CCW will release the thermistor.

Good luck.

Simon.

Gilbert K 04-30-2012 02:05 PM

STILL Blowing fuses
 
I replaced the heating element and circuit board again and blew the fuse at the 48 minute mark, about the time the heating light should come on. I opened the cover and the yellow wires were very warm to the touch. Nothing else was that warm around it. I noticed that the fuse is rated at 15 amp but my circuit breaker is a 20 amp, is that a problem.

Is there any other reason for the fuse to blow so often. Please let me know of anything else I should check.

Gene 05-01-2012 02:33 PM

Hi Gilbert,

I don't think the thermistor is somehow involved in the problem as you described it.

More likely the problem is that the motor or the heater or both of them draw more current than it suppose to. You have to measure it with the heater On and Off. The max reading for the wet heating element alone should be no more than 7 amps. You also can look for the ratings at the name plate. Post the results.


Quote:

...I checked the heater element and I had ohm readings of 57 to 95...

...Using my multimeter, the readings were again up to over 50 on my meter...
Can you describe step by step how did you do these tests please?

Also by the Ohm's law, increasing resistance with the same voltage will lead the current in the circuit to decrease (E=I*R). That means that the higher heater resistance would not cause the thermal fuse to blow.

Gene.

Gilbert K 05-04-2012 07:14 AM

Blowing termal follow up
 
Gene:

I had only tested the heater with power disconnected, either uninstalled or pulling the dwasher out, disconnecting the wires and putting the leads there. One digital meter reading varied greatly so I switched digital meters and now have a more consistent reading.

On one occassion I happend to see the heating light go on for split second then the power failed. This last time the timer was at about 48 minutes left on normal cycle when the power failed. I opened the controls and the yellow wires were very hot, hotter than anything else in the area.

I replaced the heater twice so it probably is not the heater. Are there instructs to test if the motor is drawing too much current?


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