Hotspring spa not heat up after unused for 3 months

[duke1]

I have to take the blame, as I underestimate the effort to maintain a hottub. 
that said, I moved into a house with a hotspring spa system, it was working 3 months ago. I was busy with other house repair work so I only adjusted the temp down to 80C and leave it unattended. When I checked it this week, the hotspa was half full of cold water, I drained the water, cleaned up the tub, replaced all 5 filters, however, it's just not heating up at all. 

Model: hotspring spa Watkins Grandee GO (230V, 60Hz, 40A)
symptoms: 

• Control panel: Power button solid red, Ready button no light, no error code
• Jets: all working fine, I see steady bubble from the bottom of the tub
• Filter: the main filter was ready dirty when I removed it, replaced with all 5 new filters
• Refill: I put the hose down into the main filter to fill up the tub
• Control board: LIM OK solid green, HTR OK solid red
• Heating component: I feel water is flowing in & out, but the tube is not warm at all 

I did on/off breaker few time, removed the main filter and reset breaker, but as I said the heating component is not feeling warm at all, so I doubt it is working. 

What else I should try? thanks a lot!

Andrew

[RDspaguy]

Do you have a voltmeter? Test voltage across the heater terminals on the circuit board. Post results.

[duke1]

52 minutes ago, RDspaguy said:

Do you have a voltmeter? Test voltage across the heater terminals on the circuit board. Post results.

I appreciate your help to look into my problem
On the heater relay board, that should be the voltage between H1 (black cable) and H2 (white cable)?

[RDspaguy]

Yes.

[duke1]

H1 & H2 on the heater terminal board: 0V
Red & Black on the main board: 246V

I don't see any burn spot on the heater terminal board though, any other testing I should do?

Thanks.

 

[RDspaguy]

It pretty much hs to be the relay board or main board.