Pentair Mastertemp 400 Electrical Issues
- Thread starter R.Towner
- Start date
hey guys I'm sorry but I don't have any experience with these heater boards (I don't have a heater). I have however seen a Fenwal board that looked great until I flipped it over and saw a bunch of burned traces on the back... is the back side of yours ok?
Maybe a bad board.
It's hard to tell for sure.
Try to track down exactly what is grounding out.
It's hard to tell for sure.
Try to track down exactly what is grounding out.
Check for any continuity between either of those pins to a ground. Also, check the plug for either of the wires in the same way. If it shows up as having a connection to ground, that is where to start looking. You can do this in the box where the fuse is located. Just touch one of the probes on each of the terminals and the other to ground. The board sends 24v out of one of the pins, through the wire harness to the "fireman's switch" location and back. If there is continuity to ground it will blow the fuse. Then, if there is Also be sure that the jumper that is supposed to be at the fuse location is not loose and touching the cabinet. Can't see it well in the picture. It is a small yellow wire with push on terminals on each end.
The one I had had traces that had actually melted away... which yours does not have.
But comparing the back side image to the top side image, you can see (on the top-side photo - from page 1) that it's that large-ish power resistor in the top right corner (partly hidden by capacitor c4) that got extremely hot - or at least hot enough to scorch the board. I don't know why that would happen though... i don't know what that resistor is for (is it connected to the relay below it? or something else?)
But comparing the back side image to the top side image, you can see (on the top-side photo - from page 1) that it's that large-ish power resistor in the top right corner (partly hidden by capacitor c4) that got extremely hot - or at least hot enough to scorch the board. I don't know why that would happen though... i don't know what that resistor is for (is it connected to the relay below it? or something else?)
Thanks James! that's much easier than flipping between both pages 
So the burn corresponds to the green resistor hiding behind c4
So the burn corresponds to the green resistor hiding behind c4
Definitely a bad Fenwal.
Unknown why it burned up.
You can replace it to see if that is the only problem.
It is a risk because there might be other issues that you can't really diagnose until you replace the Fenwal.
Unknown why it burned up.
You can replace it to see if that is the only problem.
It is a risk because there might be other issues that you can't really diagnose until you replace the Fenwal.
Is this what would happen if the heater was wired for 120v and it got plugged into 240v? Just wondering if maybe that happened with the previous owner or the pool guy who originally wired mine. If that's the case what else would need to be replaced? Everything on the 24v system?
Ordered a Fenwal on amazon it will be here tomorrow.
Ordered a Fenwal on amazon it will be here tomorrow.
Possibly.
Hard to tell for sure.
Typically, damaged parts from excessive current show up as burnt components.
Examine everything carefully to see if anything else looks damaged.
yyyikes! i could see from the back side image that the transformer also got hot, but those photos didn't show those scorch marks!!
if you've got a multimeter, see if the primary shorted to the secondary or the gnd tab (the board is toast, this is more out of curiosity)
if you've got a multimeter, see if the primary shorted to the secondary or the gnd tab (the board is toast, this is more out of curiosity)
- May 23, 2015
- 24,470
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Have you checked the membrane pad and control board as well for damage? Maybe there was a power surge for the previous owner and it just toasted everything.
- May 23, 2015
- 24,470
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Is there any way to test the blower motor and the gas valve independent of the internal power supply? Both of those parts are ridiculously expensive to replace and if they got blown up as well then this heater may not be worth repairing.
Little update if anyone still cares. New Fenwal went in this evening, same problem. The only time the fuse does not blow is if the lines from the fireman's switch are unplugged from the control board (J7?) I tested the wires on that and they all test fine except that they are actually quite loose on the connection to the board. I could only get a positive continuity test if I wiggled the wires at the white plastic connection point. I tried pressing all the wires in and putting a new fuse but no luck.
Seems like the only option from here is to try a new board. I'm buying all this stuff on amazon so if it doesn't work I can just send it back. Any other ideas?
Seems like the only option from here is to try a new board. I'm buying all this stuff on amazon so if it doesn't work I can just send it back. Any other ideas?
Sorry didn't see this yesterday. I looked all over the control board and did not see anything obvious. Not sure how to check the membrane pad, it's a sticker right?