Tweet
Replaced a defective Sears GDO with another similar unit. Cycled unit about 10 or 15 times setting the up and down stop limit switches. Then KABOOM. Motor capacitor exploded like a bomb. After letting it cool down I replaced it with another newer capacitor from another newer used unit. Still wouldn't work. Replaced PC board with a known good unit. When activating saw a huge spark which came from one of the 3 relays on the board. Took out the PC board and tried it on another similar GDO. The board is also fried. The components with the exception of the PC control board seem to be limited to the motor, limit switches, capacitor and interrupter infra red control at the end of the motor shaft. Don't see what could be causing the guts of the opener to destroy the PC board. If the motor windings are shorted out it might do that. Since no schematics are available I am asking if anyone else has been in this situation and what the cause was.
-
Last edited by bighank; 07-21-2012, 06:18 PM. -
I'm no garage door or capacitor start motor expert, but I happen to know that...
Electrolytic capacitors will explode if installed backwards. However, the manufacturer would have known this and should have made the capacitor so it could have only been installed one way; the correct way.
Electrolytic capacitor - Wikipedia, the free encyclopedia
Under "Polarity", see where it says:
"Most electrolytic capacitors are polarized and require one of the electrodes to be positive relative to the other; they may catastrophically fail if voltage is reversed. This is because a reverse-bias voltage above 1 to 1.5 V[4][5][6] will destroy the center layer of dielectric material via electrochemical reduction (see redox reactions). Following the loss of the dielectric material, the capacitor will short circuit, and with sufficient short circuit current, the electrolyte will rapidly heat up and either leak or cause the capacitor to burst, often in a spectacularly dramatic fashion."
Dunno how much this helps.Last edited by Nestor; 07-21-2012, 09:20 PM. -
Garage door openers have cycles per hour limits. The amount per hour is not listed, but its usually 5-10 per hr. When a GDO is cycled repeatedly the motor overheats and shuts down. After the motor cools, the OP will run again. If your cap blew, then you overheated the system to the point of no return. Usually older machines blow caps due to age, but on a new machine much worse damage can occur.
From your description and all the parts you've inadvertantly destroyed, I'd say you have a shorted motor. Sorry to say that your looking at a new GDO.Comment
-
Motror windings are aboiut 4 ohms either red or blue to white do not appear shorted
Have several of these GDOs with 1/3 and 1/2 HP motors. The GDO with the blown capacitor has the same resistance value as all of the other motors with no shorts to the case or open windings. I assume one winding is blue wire to white and the other red wire to white. Resistance is about 4 ohms for either pair and about 8 ohms if you go from red to blue (assuime thru both windings with the white wire in the middle).Originally posted by GarageTech View Post
Does not seem to be shorted or open but it blew out a second control board.
Not much wiring left on the GDO except for the limit switches, light sockets (empty), and infra red motor running sensor. Could it be the culprit? Really stymied here.Last edited by bighank; 07-25-2012, 01:28 PM.Comment
-
What's the model/brand?Comment
-
electrolytics
electrolytic capacitors do have a polarity indicator, like the ones used in a power supply. However, capacitors used on an AC circuit do not! I have both a start and run capacitor in the shop and neither of them is polarized.Comment
-
True, they do not have a polarity.Comment
Comment