Thread Number: 25500
220 Volt Question |
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Post# 392573   11/11/2009 at 18:40 (5,250 days old) by unimatic1140 (Minneapolis)   |   | |
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My '59 Philco dryer decided to stop heating last night, everything else works just fine. So tonight I took some measurements trying to determine the cause and I want to be sure I'm reading the results right. With the dryer running when I measure from point A to ground my meter reads 122 volts, when I measure from point B to ground I also get 122 volts (see schematic below). When I place one meter probe on A and one meter probe on B I get 0 volts, I believe I should read 220 volts here. I've tested the input of the cord at Red and Black and I do read 220 volts. I've tested both the High Limit and Control Thermostats for resistance and they both are closed and working properly at 0 ohms. The thing that confuses me is when I measure the two heater terminals for resistance I get 9.4 ohms (after removing the connected wires from the terminal). I would think if the heater was bad or open I would get infinity resistance. Can I assume there is a problem in the heater or am I missing something? Since 120 volts gets to each side of the heater separately can I assume that it should heat at 220 volts? What do you guys think? |
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Post# 392582 , Reply# 1   11/11/2009 at 19:31 (5,250 days old) by combo52 (50 Year Repair Tech Beltsville,Md)   |   | |
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Post# 392589 , Reply# 2   11/11/2009 at 19:59 (5,250 days old) by cadman (Cedar Falls, IA)   |   | |
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Robert, do you have a way to clip onto A and B and measure for 240v when running, with heater and everything else in circuit? It's not uncommon for a heater to go open as it warms and expands; this should let us know for sure- Your meter may even jump up a few volts if the heater goes open during the test. Cory |
Post# 392591 , Reply# 3   11/11/2009 at 20:07 (5,250 days old) by unimatic1140 (Minneapolis)   |   | |
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Thanks John. So I didn't realize I should remove the two wires that attached to the heater before testing, which now that I think about it makes total sense. So I ran downstairs and tried it. Unfortunately with the wires removed the Gray wire (point A) reads 122 volts, the Blue wire (point B) reads 117 volts. When I turn the heat switch to air dry, the value on the gray wire drops to 0 volts which is what I would expect and the blue wire remains at 117 volts. Now I'm really confused lol. |
Post# 392592 , Reply# 4   11/11/2009 at 20:09 (5,250 days old) by unimatic1140 (Minneapolis)   |   | |
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Post# 392593 , Reply# 5   11/11/2009 at 20:12 (5,250 days old) by unimatic1140 (Minneapolis)   |   | |
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Post# 392598 , Reply# 7   11/11/2009 at 20:30 (5,250 days old) by unimatic1140 (Minneapolis)   |   | |
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Post# 392600 , Reply# 8   11/11/2009 at 20:32 (5,250 days old) by cadman (Cedar Falls, IA)   |   | |
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Interesting. Sounds to me like you've got a high resistance feed to the heater (now the question is, which side?), high enough that when the heating element is in circuit the meter shows zero, but without that low-z element in place, the lightly loading meter reads appropriately. Have a 60w light bulb handy? Disconnect the heating element, then check from A to ground while running, then B to ground while running. The bulb should load the circuit enough to give us an idea if L1 or L2 is the culpret.... |
Post# 392601 , Reply# 9   11/11/2009 at 21:00 (5,250 days old) by supremewhirlpol ()   |   | |
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Yes Robert, that's what I meant. Sorry, long day. |
Post# 392607 , Reply# 10   11/11/2009 at 21:16 (5,250 days old) by unimatic1140 (Minneapolis)   |   | |
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So when I connect the meter from Violet (attached to the motor terminal) and directly to the Red side of the cord, it reads 0 volts when the dryer is operating and 110 volts when the dryer is turned off. I would think it should be reversed, no? I'm assuming the centrifugal switch shown in the schematic is drawn with the dryer turned off. Cory I would have to build a socket device to do that, what would I expect to see with the light bulb connected to each side? |
Post# 392612 , Reply# 11   11/11/2009 at 21:51 (5,250 days old) by cadman (Cedar Falls, IA)   |   | |
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Robert, What I'd expect is the bulb to light from ground to A or ground to B (heater out of circuit for all this). If you answer true for both all bets are off! Hypothetically, if it lights from ground to B with dryer running and switches properly set, we can assume the path through the thermostat and centrifugal switch is OK and we can start back tracking from A up to the source using your test lamp (still referenced to ground) to find out if it's the heat switch, limit switch or timer contacts that's bad. The idea is the lamp will pull enough current that any marginal set of contacts will reveal themselves as open whereas a meter draws in the milliamp range which still allows a continuity or voltage reading through even the highest resistance of contacts. We want that heater still disconnected as it would allow a sneak path back for your test lamp. BTW, any old 60, 75 or 100w bulb should do. Got any porcelain sockets lying around or maybe a dryer drum lamp from a parts machine? |
Post# 392636 , Reply# 12   11/11/2009 at 22:52 (5,250 days old) by unimatic1140 (Minneapolis)   |   | |
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Post# 392722 , Reply# 13   11/12/2009 at 07:37 (5,249 days old) by combo52 (50 Year Repair Tech Beltsville,Md)   |   | |
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connect the violet wire at the motor switch to the black terminal by passing the centrifugal sw this will make it heat. The centrifugal sw is one of the most common problems on older electric dryers. I usually install a 240 volt coil 30 amp heat relay in older electric dryers & combos that i intend to use to protect the timer , control thermostat, heat control sw, and motor cent sw etc. Its best to leave the heater box safety thermostat in the high current path in case the heat relay should ever stick.
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Post# 392758 , Reply# 14   11/12/2009 at 09:42 (5,249 days old) by mrb627 (Buford, GA)   |   | |
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Post# 392802 , Reply# 15   11/12/2009 at 13:39 (5,249 days old) by unimatic1140 (Minneapolis)   |   | |
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you checked across the control therm to be sure it is not open That was the first thing I checked Malcom as it is in easy access as well as the high-limit safety thermostat, both are working perfectly. John and Cory thank you both, you are both correct. First Cory, you are so right about the dryer having a switch or bad terminal that's almost open but not quite. The meter was being tricked!!! The light bulb test was pure genius! I used my interior dishwasher light assembly with a 100 watt bulb. Here is what happened, disconnecting the Dark Blue wire (point B) from the heater and connecting that wire to the light bulb, turned the dryer on and the bulb does not light. |
Post# 392804 , Reply# 16   11/12/2009 at 13:43 (5,249 days old) by unimatic1140 (Minneapolis)   |   | |
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Post# 392806 , Reply# 17   11/12/2009 at 13:46 (5,249 days old) by unimatic1140 (Minneapolis)   |   | |
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Post# 392808 , Reply# 18   11/12/2009 at 13:52 (5,249 days old) by unimatic1140 (Minneapolis)   |   | |
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Now I took John's advice and placed a jumper wire on the black terminal to the violet wire and sure enough the dryer heats. Word of caution, the jumper wire is not very thick, so I only ran the dryer long enough to see the heater working, the wire would heat up very fast and burn off if I kept it running like this. So the culprit is the centrifugal switch in the motor. Its a safety switch that doesn't allow the heater to come on unless the motor is running at full speed. Otherwise the heater could burn out if the fan is not blowing air through it. Tonight I will take the motor and switch apart and examine the contacts, hopefully they are just dirty. More pictures to come. |
Post# 392930 , Reply# 19   11/13/2009 at 00:05 (5,249 days old) by alr2903 (TN)   |   | |
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Wow, you guys could rule the world, you do know your stuff. Robert that big pulley must make the belt to what i think is the blower really go. Are philco's considered high airflow? alr2903 |
Post# 392965 , Reply# 20   11/13/2009 at 07:35 (5,248 days old) by mrb627 (Buford, GA)   |   | |
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Post# 392974 , Reply# 21   11/13/2009 at 09:15 (5,248 days old) by cadman (Cedar Falls, IA)   |   | |
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