Harman P38 shut down

[park4019]

One of my older Harman P38's shut down; no warning. Replaced it with a spare, of the same make & vintage. I've never had any problems, with either one, they always performed great. I think i've traced it to a control board problem. I replaced the three amp fuse,[it was blown, not simply burnt out]. Same problem. The fuse holder has 120v, to one side of the holder, without a fuse in it. When I insert a fuse, the voltage passing through it, drops to .2volts. I have individually disconnected the three motors, & they all run, when powered by a jumper cord to line current. The vacuum control, attached to the auger motor works, when a vacuum is applied. The control board only has two rotary switchs on it. With out a fuse, in the holder, both switchs; "blower & feed rate ", pass line current. Any advice will be greatly appreciated.

Thanks park4019

 

[gfreek]

Sure someone will chime in. Sounds like the board, but I'm not a veteran on these. There is an Ebay company that tests them and est of repair..
(broken link removed to http://www.ebay.com/itm/Harman-Pellet-Stove-Control-Board-Potentiometer-Replacement-Service-/190765984996?pt=LH_DefaultDomain_0&hash=item2c6a89ece4)

 

[Lousyweather]

could very well be a board......pigtail your feed motor, combustion blower, and distribution blower, see if they pop a breaker...if not, likely the board or a short somewhere in the wiring harness. Usually a board.

 

[rickwai]

check for a pinched wire. That is what I have found most of the time. especially where the wires go uo and around the feeder cleanout

 

[heat seeker]

There should be no voltage drop across a fuse (okay, a few millivolts). Sounds like your replacement fuse is bad, too.

You may have a bad motor. One way to search for it is to disconnect all motors and ignitor, see if fuse holds. If it does, connect one item at a time and test. The bad item will blow the fuse.

 

[park4019]

could very well be a board......pigtail your feed motor, combustion blower, and distribution blower, see if they pop a breaker...if not, likely the board or a short somewhere in the wiring harness. Usually a board.

All three motors work fine, when independantly connected to line current. The fuse thats in the board, came from my spare P38, which worked fine, when It was replaced by a P43. Only wire that I had a douibt about, was the feed from the back of the auger motor, to the vacuum switch.Although the vacuum switch & auger motor work. The wire was pulled tight & zip tied to a stand off bracket. Firtst chanc I get, I'll go back & double the the wiring.

Thanks very much; park4019

 

[park4019]

There should be no voltage drop across a fuse (okay, a few millivolts). Sounds like your replacement fuse is bad, too.

You may have a bad motor. One way to search for it is to disconnect all motors and ignitor, see if fuse holds. If it does, connect one item at a time and test. The bad item will blow the fuse.

The fuse thats in the panel now is from the P38, [older spare unit] that is now running' in place of the problem stove. Both stoves had 4amp fuses, although every thing I read calls for a 6 amp. But, they both ran, as did the one in question, until it blew the fuse. All I had was 4amp fuses, so thats what I installed. With every thing reinstaled & plugged into house current; nothing works. New fuse did not blow.

Thanks, park4019

 

[park4019]

There should be no voltage drop across a fuse (okay, a few millivolts). Sounds like your replacement fuse is bad, too.

You may have a bad motor. One way to search for it is to disconnect all motors and ignitor, see if fuse holds. If it does, connect one item at a time and test. The bad item will blow the fuse.

The replacement fuse came from the P38, that replaced the problem stove. I have no ignitor, only two rotary switchs, on the panel; [blower & feed rate]. I did disconnect al the motors & the fuse held. This one is really giving me grey hairs. The only thing I haven't checked, is the ehaust temp sensor. That will be next.

Thanks for the help; park 4019

 

[heat seeker]

If you have no voltage at one end of the fuse, the fuse is bad, or the clips are not gripping the fuse. You should have line voltage on both sides of the fuse. You mention having .2 volts at one end of the fuse.

 

[gfreek]

Check the fuse with a volt/ohm meter or diode tester by itself Not on the board. You should have continuity (0) on ohms if good. Diode mode it should beep. Does the board smell burnt or burnt spot on it?? Again sounds like not the fuse..

 

[park4019]

Check the fuse with a volt/ohm meter or diode tester by itself Not on the board. You should have continuity (0) on ohms if good. Diode mode it should beep. Does the board smell burnt or burnt spot on it?? Again sounds like not the fuse..

Tested the fuse with a ohms meter, showed continuity [0]. although my meter doesn't beep. Board doesn't smell burnt, now visual burnt spots.
park4019.

 

[park4019]

If you have no voltage at one end of the fuse, the fuse is bad, or the clips are not gripping the fuse. You should have line voltage on both sides of the fuse. You mention having .2 volts at one end of the fuse.

I have line voltage at a empty fuse holder. Install a tested fuse in the holder, & voltage drops to .2volts. Fuse snaps tightly into the holder. This is driving me nuts. I've been told that the circuit board is no longer available , & i'll have to replace it with a $305.00 update.
Thanks park4019

 

[gfreek]

i'll have to replace it with a $305.00 update.

Sorry.. Someone has to have a new-old stock board..

 

[park4019]

Sorry.. Someone has to have a new-old stock board..

I'll search for the new/old stock board first. Thanks park4019

 

[Lousyweather]

Sorry.. Someone has to have a new-old stock board..

yup, some dealers do still have the "old" boards.....

 

[heat seeker]

Is that .2 volts on the line side of the fuse? If so, your cord or outlet is bad. If on the load side, it doesn't make sense that it could load down like that without blowing the fuse.

 

[park4019]

Sure someone will chime in. Sounds like the board, but I'm not a veteran on these. There is an Ebay company that tests them and est of repair..
(broken link removed to http://www.ebay.com/itm/Harman-Pellet-Stove-Control-Board-Potentiometer-Replacement-Service-/190765984996?pt=LH_DefaultDomain_0&hash=item2c6a89ece4)

Just viewed that site, looks like it may be the way to go. Sent him a e-mail, with my problem & what i've done to diag it. Thank you very much for the help.
park4019

 

[park4019]

Is that .2 volts on the line side of the fuse? If so, your cord or outlet is bad. If on the load side, it doesn't make sense that it could load down like that without blowing the fuse.

The .2v , is on the load side of the fuse holder. I tested the outlet, & it has line voltage. I just sent a e-mail to a e-bay site that gfreek mentioned. They rebuild circuit boards. Thanks park4019

 

[heat seeker]

I know I'm being kind of stubborn here, but how about one more check, which might save you some $.

With the unit unplugged, measure the resistance from the hot blade of the plug to the load side of the circuit just past the fuse holder. It should read about 0. I just can't figure out why the fuse isn't blowing.

 

[gfreek]

I just can't figure out why the fuse isn't blowing.

Maybe there was a power surge of some sort or one of the motors drew too much amperage for some reason.......Kinda wonder what the amp draw is on them.. Might not be able duplicate what happened...

 

[heat seeker]

Maybe there was a power surge of some sort or one of the motors drew too much amperage for some reason.......Kinda wonder what the amp draw is on them.. Might not be able duplicate what happened...

True, but that doesn't explain why he has line voltage at one end of the fuse, and essentially zero volts at the load end without a blown fuse or bad connection. Electricity just doesn't work that way.

 

[gfreek]

True, but that doesn't explain why he has line voltage at one end of the fuse, and essentially zero volts at the load end without a blown fuse or bad connection. Electricity just doesn't work that way.

Agree. Does not make any sense....

 

[SwineFlue]

True, but that doesn't explain why he has line voltage at one end of the fuse, and essentially zero volts at the load end without a blown fuse or bad connection. Electricity just doesn't work that way.

That's perfectly normal if you're measuring voltage across a good fuse.

 

[gfreek]

One probe should be on neutral and other probe on end of fuse, AC volt setting... Assuming this how par4019 did it.

 

[park4019]

I know I'm being kind of stubborn here, but how about one more check, which might save you some $.

With the unit unplugged, measure the resistance from the hot blade of the plug to the load side of the circuit just past the fuse holder. It should read about 0. I just can't figure out why the fuse isn't blowing.

I measured, as you said. I have 0 at the load side of the fuse holder, & accros the fuse. Pluged the cable into outlet, & .2v, at load side of fuse jolder, & .2v at feed side of fuse holder.