I went ahead and ordered the float switch... if it doesn't work, then we'll know that isn't the problem, and if your theory is correct, then it is likely a bad control board. So I've scheduled GE Appliance Repair to come out this Friday and have a look at it. At least I will have done 90% of the diagnostic work at that point :)

Thanks for your help, ApplianceMan, and if you have any more ideas, please feel free to post them here.

Oh - I read that article on using an Ohmmeter - very timely. I'll go back and do that measurement again, armed with some knowledge this time.

Okay - I removed the door, and found the technical instructions for various error codes posted there. There are two suggestions there that I found that were not already done: One is to check and see if the water flow is more than 10 seconds longer than it is supposed to be - cause that means it's out of spec. If it is, it says something like "replace the control". Yeah - what control?

The other suggestion is to check the "wire harness". Since I had the door off, I did check as many connections as I could, including those to the control board (I even removed the control board cover to get at it and examine it). They all seemed okay.

I also checked the resistance on the float switch again. It is reading OL when open, and puts up numbers when I depress the switch. I'm assuming that means it's okay, although I did order a new switch a couple of days ago.

Any thoughts?

Here's an update on this still-untractable problem:

On Dec. 11th, GE Appliance Service came out and spend some quality time diagnosing the problem. After checking everything from the float switch to the wiring cable harness, the tech thought that he had found the magic solution - it all seemed so simple: He said, "Just touch the "start" button and the "clear/reset" button at the same time." It seemed to work. I thought, "Wow - that was easy - why didn't I think of that?" Indeed, the technician guidelines posted on the inside of the door seemed to suggest just that.

But not so fast. The day after the tech visit, I ran the dishwasher in the rinse/hold mode late in the evening - no problem. But sometime during the night, I woke up and heard the dishwasher beeping - several hours later. I got up and took a look at it - and, sure enough, there it was beeping the C4 error once again.

I touched the "start" and "clear/reset" button - but nothing happened. Turned off the power, turned it back on, and did the same thing - still nothing. And that is where it stands - it is still delivering the same message.

Now, the inside of the door sticker (it's not a "mini-manual - just a sticker with info for the repair tech) suggests several solutions, including replacing the inlet water valve - which I have done. The float switch was also replaced when the tech was here.

It also suggests checking the wiring harness, which the tech also did. The only suggestion that has not been followed up on is this: It states that if the water fill time if 10 seconds longer than spec, that the control (control board?) may need to be replaced. The tech did not check that to the best of my knowledge.

I called GE appliance repair again, and they told me over the phone (in addition to scheduling another visit on Jan. 8th) that there could be a check valve issue. He said there is a check valve coming off the drain side of the pump, and said this was, to the best of his recollection, in the right rear of the machine. This was also suggested to me by someone else, as follows: "We would suspect a check value issue and water is seeping back into the sump and triggering the overfill fault".

So this looks like the next avenue to explore. But two questions: Just where is THIS check valve? Is the tech right - it comes off the pump in the middle of the machine? Looking under there, I see the drain solenoid assembly, and the motor, but not seeing a hose coming off off that pump/motor thing. Is it visible from the back of the machine, and accessible from there? Is he referring to the thing that the plunger assembly threads into, below the filter screen in the rear of the dishwasher? I have a picture of this, and it looks like there is a check valve gasket there, but I would have to access it from the rear of the dishwasher, or pull the dishwasher out of its enclosure, which would be a herculean task (for reasons I won't go into here).

Can you verify that this is the check valve that this is being referred to by both the tech and the other person who provided me advice?

Any other thoughts - such as, would the C4 error with the machine suddenly beeping a code in the middle of the night be consistent with a failed check valve?

Hey, Appliance Man -

I did find the check valve, but not before cutting a large hole in the cabinet panel directly behind the dishwasher, based on the advice I got from the GE appliance service tech :mad: So add the costs of having my cabinetry guy make a replacement panel to the $400 or so I have already spent on this dishwasher since last summer (the bulk of that was an earlier visit to replace the control board).

So after cutting away a large hole in the back cabinet so I could reach the putative location of the check valve, I found that there was no check valve there. In fact, on this machine, it is in the front - easily accessible. I guess I could have checked the dishwasher body schematic, but I decided to trust what I was being told over the phone. So, chagrined, I removed the hose from the check valve, unthreaded it and removed it, and - voila! - found the little rubber gasket with a flapper - the check valve! I was told to look and see if it was distorted or otherwise. Indeed, it is - the flapper part is intact, but it is sitting in a kind of open position.

Now how would that cause a C4 error? I don't really know. I'm just putting blind trust into advise given me by people who supposedly know more than I do on the subject. Maybe it is misplaced. In any case, I went online and found that this outfit doesn't carry the check valve anymore, so I had to source it elsewhere. Also, you can't just buy the 20 cent rubber check valve part - you have to buy the whole check valve. So add another $20 to my bill. It will arrive around Jan. 5th, and the technician is scheduled to visit on January 8th. Maybe there is some magic connection here between the check valve and the C4 error - I can only hope, even if it doesn't seem to make sense.

Any further thoughts? You should know that the dishwasher DOES have a high loop in the drain - I ascertained that while doing the check valve. If it's not the check valve, could it possibly be that I have a bad control board - notwithstanding that it was replaced only a few months ago?

Hey, Appliance Man -

Just to clarify - the GE appliance guy didn't suggest I cut a hole in the back panel behind the dishwasher - he only said that he thought the check valve was somewhere in the back of the dishwasher, so I took it upon myself to cut the hole to access it, rather than try to pull out the dishwasher, which seemed like the lesser of two evils. The reason is because the front of the dishwasher has been tiled in, and I would probably have to break and/or cut tile to get it out, so until I know the dishwasher is dead and not repairable, I'm not going to do that. So blame me (largely) for destroying my cabinetry, albeit I did get bad advice on that point.

Your point is well-taken: "I was under the impression that there was no water in the washer when the code came up." That is correct. There is no water in the tub when the code is flashing. But at this point, I am grasping at straws, and it seemed worthwhile to give the check valve theory a try. It that doesn't work, I'm going to have to suspect the control board, notwithstanding that it was replaced back in July/August. It may be a bad board. Your thoughts?