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LG dishwasher no power to heater element


GrayRat

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Hi everyone. Our LG dishwasher started leaving everything dirty suddenly. The unit is not showing any error codes.  I noticed the wash water is cold. The heater element seemed OK at 12.5 ohms. I put a multimeter across the 2 legs during a quick cycle and it shows 0 volts AC. Anybody got any advice on my next steps?    Thanks!

 

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Sorry John, yes, a model number would be nice.  The dishwasher in question is an LG LDW8072ST.  A little more info:  I followed the wires from the heating element back to a small poached egg shaped device.  This device has the 2 heater wires coming out of it, and 2 more going into it.  It also has a water hose connecting it to the plenum that the heater element lives in.  There is no voltage going into or out of this device, either.  Following the wires upstream further, they lead into the door.  One goes directly to the electronic control board.  The other wire detours through a switch on the door opening handle, then to the control board. 

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LDF8072ST

Question:

Is your water Heater...a *tankless* or tank (ie, 30 or 40 gallon)?

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My water heater is a tank, and has been situated far away from the dishwasher for the last 15 years. To be clear, the dishwasher has performed nicely until exactly 3 days ago.

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Is the dishwasher hot immediately after the cycle ends?

Note:

The heater is only used twice during the cycle.

First is during the Main Wash cycle (about halfway through the cycle)

The second is during Final Rinse (near the end of the cycle before the Dry Cycle begins).

 

Edited by john63
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If the cycle ends...and is cold inside...that is a big clue for diagnostics purposes.

If the dishwasher is hot...then the heater is not a factor at all...the problem lies elsewhere.

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Is the dishwasher connected to the Hot Water pipe (i know...stupid question...but should be ruled out).

Since water heater is some distance from the dishwasher...is the hot water turned on at the sink prior to beginning a cycle?

26 minutes ago, GrayRat said:

The wash water is cold throughout the wash cycle.

What is temperature of the water entering the dishwasher during fill?

Is there *any* heat inside the dishwasher at the end of the cycle (not just the water temperature) ?

If no heat whatsoever...and the left side door switch tested okay (continuity)...replace Main Board.

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Yes, the dishwasher is connected to the hot water pipe.

No, turning on the hot water tap is not part of our routine before running the dishwasher.  Sometimes we happen to do it, other times not.  Ok, perhaps that's not a best practice, but my point is, the temperature of the input water to the dishwasher hasn't changed.  It varies, somewhere between tepid and hot.

Last night I ran 2 cycles and the heater was working again.  Nice clouds of steam billow out when you open the door mid cycle, and the wash water is hot again.  I could see 117V across the heater several times during the cycle.

Why did it start working again?  I have no idea.  But I suspect it's only temporary.

John63, is the "left side door switch" up where the handle is to open the door?  Is it part of the handle, or is it a separate sensor?

 

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At this point...it appears that the Heater and related components/circuits are not at fault.

An intermittent Heater is just not a trait of LG dishwashers.

Four things to try next...

1. Clean filter in Sump...if cannot be adequately cleaned...replace it. This is *very* important.

2. Run a Clean Cycle with Dishwasher Magic (available at Lowes/HD)

3. Switch to Finish Powerball Quantum Max detergent.

4. Add Rinse Aid to dispenser.

Try several cycles.

 

 

 

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1 hour ago, GrayRat said:

Where does the heat for the dry cycle come from?

The Heater is never used during the Dry cycle.

Heat left over ("saved") from Main Wash and Final Rinse is used for the Dry Cycle.

This is accomplished by 2 things...

1. Stainless steel tub (plastic tubs cool nearly instantly).

2. Insulation (wrapped around ss tub).

A blower fan within the door...pulls moisture out during the Dry Cycle.

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