Speed Queen ADE30RGS171TW01 No heat, head-scratcher

[norwood]

Got this dryer for free in known broken condition. Runs, doesn't heat. The fellow who gave it to us said he'd been told it "needed a thermocouple," but that he and his wife had another dryer at the house and switched to that one instead.

 

Figuring that he had meant thermostat, I started out by ohming out the cycling thermostat, limit thermostat, and thermal fuse. All showed continuity. Heating element tested good (10 ohms, as I recall). OK, that's a little weird. Hooked it up, tested it again, no heat. Disconnected from power.

 

Following the wiring diagram, I looked at the temperature select switch, but it tests good (continuity across whichever two contacts are selected).

 

OK, I see current is supposed to go through the timer. It showed high ohms when I tested it disconnected, and I thought I had found the problem, but I'm now wondering if I tested it incorrectly since I was trying to hold down the "hold down to start" timer while ohming it out.

 

Connected test leads (with jumpers carefully arranged to keep them from shorting anything - I've shocked myself enough times in younger years to be careful), full voltage at timer, full voltage at mode switch, full voltage at cycling thermostat, full voltage at limit thermostat, full voltage at thermal fuse and full voltage at BOTH ends of the heating element? Eh?? So I would think "bad ground", but there's also basically no resistance between the heating element and ground. I don't get why there'd be no resistance, but also no current flow. Yes, there is 220 to the dryer, I also checked that with the multimeter.

 

I seem to remember components being able to fail such that they could flow a very small amount of current (like a multimeter would supply), but so that they'd act like an open circuit when asked to flow a lot of current. Is there a way to see whether that's happening here without shotgunning parts at it? Or should I be looking somewhere else entirely?

 

Thanks in advance!

[ECtoFix]

2 hours ago, norwood said:

Connected test leads (with jumpers carefully arranged to keep them from shorting anything - I've shocked myself enough times in younger years to be careful), full voltage at timer, full voltage at mode switch, full voltage at cycling thermostat, full voltage at limit thermostat, full voltage at thermal fuse and full voltage at BOTH ends of the heating element? Eh?? So I would think "bad ground", but there's also basically no resistance between the heating element and ground. I don't get why there'd be no resistance, but also no current flow. Yes, there is 220 to the dryer, I also checked that with the multimeter.

full voltage at BOTH ends of the heating element?

Sounds to me like you're referencing ground for your voltage tests.  That is an improper test procedure since GROUND is NOT part of the circuit energizing the element.  The element is powered from two separate legs of 120v (usually denoted as L1 and L2) that are out of phase with one another, providing 240v to the element.  Since the element isn't heating, I'll bet that if you connect your voltmeter leads to each end of the element, you'll read 0v.  As such, you are lacking one of the 120v legs and should look for the open in the circuit that's causing it.

With the dryer plugged in and running, you should first read 240v across L1 and L2 of the input terminal block.  If you are, then proceed with making voltage reading in the dryer's 240v circuitry.  There IS a 120v circuit in there too.  That's for the control circuit and uses one of the line voltages and neutral to derive that.

No resistance between the heating element and ground.

Just what exactly do you mean by no resistance between the element and ground?

Although I don't have a schematic to refer to, I'm certain that resistance between those test points should (ideally) read MAXIMUM resistance. 

• On an analog multimeter, the needle would remain pointed at the infinity symbol (∞). 
• A digital meter should show OL (for overload). 

Those resistance reading indicate there's too much resistance to measure.

So, if you're reading NO resistance to ground, THAT would be a direct short and should trip you circuit breaker.

[norwood]

Voltage at the heating element: Good call, I was indeed referencing ground and that was confusing everything. I knew I was doing something dumb, thanks for helping me figure out what it was!

 

As for no resistance between the element and ground, that part I was not describing accurately. What I should have said was no resistance between the element and the second hot terminal. So the open circuit wasn't there.

 

After all that I went back and went at it again, methodically. With the test leads applied to the mode selector and the #2 hot terminal, 10 ohms resistance. With the test leads applied to the red (from #1 hot terminal) and orange (from timer to the rest of the heating circuit), machine running and calling for heat, open circuit, infinite resistance.

 

So after all that, sounds like it was just a bad timer. Is that something that goes bad on these Speed Queens? Sorry, I knew the answer was going to involve that I was making a new-guy mistake.

[evaappliance]

yes, usually the orange wire marked H  on the timer will have the terminal discolored from heat buildup when there is a bad timer, sometimes you will even have to replace the wire end too