Kenmore model 70 has no heat. Last year, I replaced the themal cutoff switch after losing heat. At the time, I was able to locate the open circuit at the cutoff switch, replaced it, and all was well.
Now, I have no heat, but the coil is receiving 240v as normal. Coil reads out 10.5 ohms, and is listed as 7.5-11.5 as within normal range.
For measure, I have bypassed thermostat and thermal cutoff - no help. Coil still receives 240v, but does not heat up.
It seems as if the coil is bad, but how would it be measuring the correct resistance if it’s toast? I’m not an electrician, I don’t know!
Also, worth noting is that I have measured coil input with main ground input. When grounding to the coil housing, it only appears to have 120v. Don’t know if this is normal.
Sorry about the model number. It’s a Kenmore Series 70, model no. 66722694.
I checked input voltage to the coil by first grounding multimeter to the dryer’s main ground off of incoming AC, then probed positive at both of the external coil terminals. Both showed good 240v. Also probed positive inside the coil housing to eliminate possibility of bad connection - this also showed good 240v passing through the coil.
Thermostats, thermal cutoff switch, and coil all passed continuity tests - has me stumped!
The original problem that I was trying to solve was an extremely long cycle. I had thought that the selector/timer assembly was broken, but it was at this point that I noticed the coil was not coming on and there was no heat.
The timer motor still works fine when set on timed dry, and all other positions appear to operate normally. However, last few nights the “auto dry” setting had the dryer running for well over several hours. I believe this is due to the coil not coming on.
Remove the terminal cover (#1 on the diagram). Measure the voltage at the terminal block (the dryer door open) between the central wire (neutral) and each end wire. It suppose to read about 120 VAC. Measure the voltage between the end wires. It suppose to read about 240 VAC. Post the results.
[COLOR=“Blue”]I checked input voltage to the coil by first grounding multimeter to the dryer’s main ground off of incoming AC, then probed positive at both of the external coil terminals. Both showed good 240v. Also probed positive inside the coil housing to eliminate possibility of bad connection - this also showed good 240v passing through the coil.[/COLOR]
I may be missing something but if I read the above correctly something weird is going on.
If one meter lead is on the unit’s frame/ground, then you should not be able to measure 240 volts. When referenced to ground the max you shoud see is 120 volts.
Sounds like the unit may not be properly grounded.
If you see 240 volts at both sides of the heating coil then there will be 0 volts across the coil it so it will not heat.
You must measure across the coil.
If a 3 wire hook-up. I would check that the unit has a ground strap from Neutral (center terminal on the unit’s terminal strip) to it’s frame.
If a 4 wire hook-up. I would check that the line cord’s ground wire (usually green or bare) is connected to the unit’s frame and that there is not a ground strap from Neutral to the frame.
Let me explain.. I’m not used to working with 240v so I’m not sure what I’m supposed to see. At first, when probing positive at the coil terminals, and using the unit frame for ground, I saw 120v at the coil. Then, when using the ground terminal on the incoming AC for ground, I see 240v at the coil. I wasn’t sure which was the right way to check it.
Will check for continuity at ground.
Should I be seeing less voltage on one side of the coil?
Well.. If nothing else I figured one thing out. I pulled out the coil assembly and wired it up to a test wire and plugged it in. It heated up. Coil is fine, it’s something else. Continuing on.
Looks like I might have found the problem. Pulled the timer assembly and opened it up. The contacts for main positive (RED) are completely burnt out. Probably enough for multimeter to show 120v, but not enough current passing through. If I can’t fix up the timer, I’ll replace it.
[COLOR=“Blue”]I’m not used to working with 240v so I’m not sure what I’m supposed to see.[/COLOR]
240 is not really hard to understand.
Basically your unit has two 120 volt AC supplies when measured to Neutral.
The 2 supplies are 180 degrees out of phase. As an example when the L1 supply is at positive 120 volts, the L2 supply is at negative 120 volts. So when you measure from L1 to L2 you see 240 volts.
The reason they do this is because power/wattage is voltage times amperage.
So to get the same power out, if you double the voltage you can half the amperage. Since the amperage is half they can then use a much smaller gauge wire and this saves loads of dollars.
The heater circuit is not connected to Neutral and should only rely upon the 240 volt AC.
When you measure any where on the heater circuit using Neutral/ground, you will normally always see 120 volts but it really does not tell you much because you cannot tell which side of the line you are reading.
Hope I explained this OK and that you will find it useful.
Installed replacement timer today and the dryer is now working again 100%! Thank you very much Gene and denman for all of your help! This is a great site!
