Won't heat past 92 degrees

[cubeconvict]

I have a 'Newporter' spa from Costco which has all Balboa internals.  It won't heat past 90 degrees right now. The tub has a VS model controller box with a board labeled FREE300. It shows the firmware version on boot, but no error codes. It goes right to "PR" and behaves normally except for the ceiling on the temperature. The pump was replaced about six months ago and behaves normally.

Here is what I have done so far:

• Turned it off and then on again many times.
• Drained and refilled
• Swapped the temperature sensors
• Removed and reinstalled the temperature sensors (not replaced)
• Tested the sensors, they give an approximately 40k ohm resistance at household room temperature
• Followed the procedure to reset the resident memory by putting a jumper across the two pins on the board.
• Also did the dip-switch reset procedure recommended for other boards in the series.
• Tested line voltage where connected to the board.
• Tested line voltage at the nearest junction box.
• Also tried changing the filter cycle times ( I had set it way down after overheating during the summer)

I am not in a financial place where I can start swapping parts unless I am sure it will fix it.  Is there some way to diagnose for sure which part is failing?

[CanadianSpaTech]

Post photos of the circuit board. Does the heat indicator light come on on the topside. First it will flicker for 30 seconds and then go solid. Once it is solid test for 240V at the 2 heater lugs on the heater tube. If you don't get 240V then you likely have a bad heater relay on the board. Remove the board and have a look on the back for darkened or burnt areas around the K2,3,4 relays. Relays are fairly cheap ($20) and can be replaced but you either need the correct soldering tools or find a local electronics repair shop that can do the work for you. I normally have them replace all the relays to freshen up the board.

Where are you located?

Post results

[cubeconvict]

Okay I checked across the two lugs and was getting like 0.5 V so that's the right direction.  It's raining right now, so I don't want to take the board out until we have some dry weather. 

If I understand what I see on the relays, I won't be able to test them until I get to the back of the board. Is that right?

[CanadianSpaTech]

Sometimes when you look in the back it is obvious the relay has failed but not always.

Follow the power. In the bottom photo it shows the relays. Please be careful and do not exceed your knowledge and ability. Test for AC White to the open tab in the top relay. Then the top black wire connection. Then test white to the bottom black wire connection and last the bottom relay open tab. (Solid heat light on topside) Where does the power end.

[cubeconvict]

Here's the front and back of the whole board with each of the relays numbered. There's no distinct charring or anything.  There seems to be discoloration on the back of #2, but it isn't dramatic enough for me to be sure.

[cubeconvict]

Oops, turns out that what I marked as 2&3 are actually labeled on the silkscreen as k3 and k2. I also realized that I had the boxes I drew shifted funny and was not actually marking theme correctly. Shift the boxes I drew up a tad and they would cover the correct solder pads.  It looks clean enough, I am going to put it back in and test as described.

Also, I had forgotten before to check the fuses.  They are both okay.

The heater measures at 15 Ω