P38 problem

[Firemedic16]

New to this site, please help.
I just cleaned my Harman P-38+ stove, I also replaced the two pots on the control board because of dead spots and poor performance. ( I do have some PCB soldering experience ) When I finished, I plugged the stove in and the exhaust ( flue ) fan came on and will not turn off.
I did vacuum around the sensor in the flue pipe, but was careful not to bang it

Thanks for any help.

 

[Lousyweather]

could be the ESP just failed......that's about the only thing other than the circuit board

 

[DAKSY]

New to this site, please help.
I just cleaned my Harman P-38+ stove, I also replaced the two pots on the control board because of dead spots and poor performance. ( I do have some PCB soldering experience ) When I finished, I plugged the stove in and the exhaust ( flue ) fan came on and will not turn off.
I did vacuum around the sensor in the flue pipe, but was careful not to bang it

Thanks for any help.

First thing I'd do is pull the ESP, clean it & inspect it. Careful as you may have been, it may be damaged.

 

[Firemedic16]

I was thinking it might be that sensor, does anyone know how to troubleshoot it ? Example; unplug it and the fan goes on, measure the resistance across the pins ?, etc..

Thanks

 

[MCPO]

If this all happened since you installed the new pots it might very well be that you damaged the control board with excessive heat , or a piece of solder is shorting a board circuit.

 

[P38X2]

If this is the old 2 knob style board, and the temp knob is turned to on, this is exactly what the stove is supposed to do. Is the temp knob turned to off?

 

[Firemedic16]

If this is the old 2 knob style board, and the temp knob is turned to on, this is exactly what the stove is supposed to do. Is the temp knob turned to off?

The temp knob is turned off.

 

[P38X2]

The temp knob is turned off.

Ahhh, OK. Didn't wanna assume you had it off.

 

[Firemedic16]

If the ESP incorrectly sensed a high heat reading, wouldn't the exhaust fan stay on and the auger motor not turn on ?

 

[rayttt]

New to this site, please help.
I just cleaned my Harman P-38+ stove, I also replaced the two pots on the control board because of dead spots and poor performance. ( I do have some PCB soldering experience ) When I finished, I plugged the stove in and the exhaust ( flue ) fan came on and will not turn off.
I did vacuum around the sensor in the flue pipe, but was careful not to bang it

Thanks for any help.

Which PCB do you have in the P38?
I just replaced mine from the old one to the new one.
The new one has a bunch of LED's on it..the old does not have any LEDS.


If its the new one there should be a blinking status LED blink I think 3 times to say it can sense the ESP probe.


When I connected the ESP probe to my new board..it had a problem with plug..the metal pins pushed out of the plug making a bad connection and giving me the blinking status.

If you have the old board...then double check the connection.
to ohm out the ESP probe Id imagine it as a set resistance for a set temperature..
While ohming it out...Breath on it or do something to change the temp of it and verify that the Resistance changes.

 

[Firemedic16]

Which PCB do you have in the P38?
I just replaced mine from the old one to the new one.
The new one has a bunch of LED's on it..the old does not have any LEDS.


If its the new one there should be a blinking status LED blink I think 3 times to say it can sense the ESP probe.


When I connected the ESP probe to my new board..it had a problem with plug..the metal pins pushed out of the plug making a bad connection and giving me the blinking status.

If you have the old board...then double check the connection.
to ohm out the ESP probe Id imagine it as a set resistance for a set temperature..
While ohming it out...Breath on it or do something to change the temp of it and verify that the Resistance changes.

Thanks rayttt,
I have the old pcb, here is a new twist. I started the stove today, not expecting it to work. After a few minutes the auger motor kicked on and it's working like a champ.... Except it will not turn off, I am thinking I have a bad pot.

 

[rayttt]

Thanks rayttt,
I have the old pcb, here is a new twist. I started the stove today, not expecting it to work. After a few minutes the auger motor kicked on and it's working like a champ.... Except it will not turn off, I am thinking I have a bad pot.

Im thinking you may have a loose connection somewhere on PCB that may be causing flaky intermittent problems..
Make sure all those lugs are tight and on correct terminals..

if its on and running ..if you gently and carefully take the bunch of wires in your hand and move them around a bit does things turn on and off?

 

[Firemedic16]

Im thinking you may have a loose connection somewhere on PCB that may be causing flaky intermittent problems..
Make sure all those lugs are tight and on correct terminals..

if its on and running ..if you gently and carefully take the bunch of wires in your hand and move them around a bit does things turn on and off?

Checked, not a loose connection, at this point I am leaning toward a bad pot. Could be worse.

 

[Bioburner]

Three dollar pot plus time is not serious yet. I have a pot that likes to fire up the stove on its own. Got a bigger stove with better fan that we have run through several shake down firings now so will attempt replacing all the pots. Snow flurries in forecast for next several days

 

[Firemedic16]

UPDATE:.
It was a POT problem. The feed POT must have 50k ohms to keep the exhaust fan off. Mine measured 43k. The supplier from Maine was kind enough to measure some in his inventory and sent me two new ones that were the correct resistance. Installed them and stove is working great.
Lesson learned, don't always believe the number stamped on a part.

 

[Bioburner]

Glad to hear you solved the problem. Still have to replace the pc45s pots.

 

[Lousyweather]

I seem to recall that the directions say that when you replace the board on a P38, youre also supposed to replace the ESP probe. Since the ESP controls the distribution fan, I wonder if that might not be related to the low potentiometer reading on the original pot....?

 

[Bioburner]

The P38 had a new generation of board for replacement if memory serves right hence the updating of the ESP as well.

 

[Lousyweather]

The P38 had a new generation of board for replacement if memory serves right hence the updating of the ESP as well.

yea, but this goes back to when the P38's had the "little" boards......

 

[Bioburner]

yea, but this goes back to when the P38's had the "little" boards......

Firemedic stated that his is the old pcb.

 

[Lousyweather]

yup,

Firemedic stated that his is the old pcb.

but its even true on the "old" boards as well ("old" boards = "little" boards)