Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

Blowing the famous 3 amp control power fuse on air handler control board


Jakaround's Avatar
Member

Join Date: Mar 2017
Posts: 3

03-20-17, 04:29 PM   #1 (permalink)  
Blowing the famous 3 amp control power fuse on air handler control board

Well I've looked and can't seem to find the answer I'm in search of so here goes. As the title states, I have a blown 3 amp fuse on the control board located in the air handler. This is a split unit with a remote heat pump outside. (Goodman ARUF48D14AC air handler and VSZ140421AA heat pump) On the chance it was just a bad fuse, I replaced it and it blew again after approximately 3 mins of air handler and condenser operation. After reading some other posts, I checked the contactor in the remote unit, it cycled normally and coil read no continuity to ground but I replaced it anyway. Still blew the fuse. Replaced the defrost control board (PCBDM133) and retested, blew the fuse. Finally I disconnected all low volts wires at the air handler and tested individually to ground and found a short to ground on the orange wire. Disconnected the orange wire at the heat pump and the short to ground was on the heat pump side (not the house side). Orange wire goes to the defrost control board (terminal O). I disconnected the orange wire from terminal O and the short to ground was on the board. The O terminal is tied to the O-rv terminal (reversing valve) on the control board. Pulled the 2 black wires for the reversing valve solenoid from the control board and the solenoid itself is not shorted to ground although the reading across the solenoid is zero. The black wires for the reversing valve solenoid go to terminals O-rv and C-rv on the DCB. Reading C-rv on the DCB to ground is a short (just a common line I'm guessing). This tells me that the solenoid is completing a path for current flow from O-rv to C-rv. Basically, I'm just at a loss here. Should the solenoid not be completing the circuit right now? Is the reversing valve solenoid bad or possibly just stuck? Any help would be greatly appreciated. Thanks in advance, sorry for such a long post.

 
Sponsored Links
PJmax's Avatar
Group Moderator

Join Date: Oct 2012
Posts: 39,440
NJ

03-20-17, 04:35 PM   #2 (permalink)  
Welcome to the forums.

If it weren't for the famous 3A fuse... a lot more people would have a lot more major damage to repair. That fuse protects the board and transformer from frying.

If you were running the system in A/C mode then you were sending power to the contactor and to the reversing valve. So.... one of those two is the problem.

Basically, you need to check the resistance on the contactor coil and the reversing valve coil although it appears your reversing valve is the problem here.

Apprrox resistances.... 20 ohms on contactor and reversing valve.


~ Pete ~

 
Jakaround's Avatar
Member

Join Date: Mar 2017
Posts: 3

03-20-17, 05:01 PM   #3 (permalink)  
Totally agree with you, without that fuse, bad things could happen. So the 2 black wires connected to O-rv and C-rv terminals are the wires to the reversing valve solenoid right? This is reading zero so that equals high current which equals blown fuse. Now just need to find and order a solenoid and figure out how to replace that. Thanks for the quick response. I'll update with the results.

 
PJmax's Avatar
Group Moderator

Join Date: Oct 2012
Posts: 39,440
NJ

03-20-17, 05:21 PM   #4 (permalink)  
Yes.... 0 ohms between the two wires is a dead short.


# B1225022 SOLENOID COIL (You have a Goodman M15 series unit.)

Available many places.....here's just one.
B1225022-Replacement-Goodman-Reversing-Solenoid


~ Pete ~

 
Jakaround's Avatar
Member

Join Date: Mar 2017
Posts: 3

03-22-17, 04:20 PM   #5 (permalink)  
Update

I promised an update and here it is. Well, I installed a new reversing valve solenoid coil and had the same problem. I believe that I was using the audible continuity indicator on my multimeter and did not pay attention to the actual resistance reading, so I thought I found my short to ground, WRONG. (PJ, you mentioned the new coil should be about 30 ohms, old one read 14 ohms and new one read 16 ohms, just passing on that info.) I was running out of parts and ideas to throw at this thing so....I called a shop. Guy came out and popped in a 5 amp resettable breaker instead of the 3 amp fuse :NO NO NO:, I made a comment about the higher current possibly damaging something but he assured me that he has never seen anything like that happen before. Surprise surprise, what happened? He fried my 24v transformer and replaced "for free" because he caused the failure. Anyway, he had to call in reinforcements, another guy showed up and they spent 5 hours going up and down from the attic to the heat pump and back again. Finally he came in and he said that they think they found the problem. The issue was a shorted to ground low voltage wire (one of the wires I had checked). The amplifying condition was that the short was only noticed after ~3 mins of heat pump operation and I never did any clamp on ammeter checks during operation. (It was the red wire going from the air handler to the heat pump). They did not mention a specific location of the short, they just swapped to a spare wire. Additionally they pointed out multiple issues with my new construction home with brand new HVAC system including: a small refrigerant leak, strip emergency heaters not connected at all (which checks with chart due to not having heat when set to emergency) and no float switch installed on the condensate overflow pan (required by code for attic installed units from what he said). Obviously he attempted to up sell the repairs and sell me a maintenance package which I kindly declined but I do know what company to call if I find myself in a bind again. Out the door I ended up paying $51 for the contactor relay and DCB another $36 for the solenoid coil (all replaced by me) then $49 for the service call and $100 for the Low Voltage Wiring Repair. Ended up getting a "free" transformer out of the deal but all together spent a grand total of $236 and my heat is working again with no famous blown 3 amp fuse. And actually working better now that the aux heat actually works. Not sure what signal was being sent from the AH to the HP around the 3 - 4 minute mark but it was being shorted to ground and blowing the fuse. Take away what you will. PJmax, thank you for your help, I look forward to using this site more for more DIY stuff and getting good advice. The only advice I could suggest is getting a resettable 3 amp fuse and a clamp on ammeter for the most comprehensive troubleshooting (or just a bunch of 3 amp fuses). DO NOT install a higher amp fuse in its place, you WILL damage something else. Thanks again

 
Search this Thread