Spa pak 153whg- Wiring and heater issues.


Jan 4, 2021

I am in need of dire help and at wits end with my heater. I recently changed the Spa PCB, unitherm governor, high limit switches,pilot generator, and pressure switch this week. Before nothing would work and now I can’t manually get the pilot light to turn and stay on. For some reason I couldn’t get the furnace to kick on.
I tried drawing up my own wiring diagram, but for the life of me cannot figure out how the wires need to be configured between the white/red from PCB, the combination valve, toggle, and thermostat control knob.
I am getting ~625mV out of pilot generator (pilot stays on), no voltage from PCB (I am guessing because I have it wired incorrectly).
I assume I first need to see how to correctly wire the system and then find out if my combo valve is bad or not.
All help would be truly appreciated! Thank you.


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Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Is this a pool heater or spa heater?

What manufacture and model?

Show us pics of the labels and data plates on it so we know what you are working on.


Jan 4, 2021
Spa heater
Brand: ray pak
Model: spa pak
Model#: 153WHG
The heater is from the early 80s and obsolete. I have still been able to find OEM parts from Amazon and other places though.

I have tried drawing up a wiring diagram, but it’s incomplete. I do not knowwhat goes where between combo Valve, toggle switch, and control panel. Thecontrol panel has a firemen’s (white) and a wire to the heater (red). Basically, I know how to and have ran the series from pressure switch-145 limit-splice-135limit. I also wired back up the pilot generator and that works good so I know I wired that correctly.


Well-known member
Mar 30, 2019
Las Vegas, NV
The wiring diagram that you drew doesn't make much sense. The honeywell gas valve seems to have a date code from 1982. Your gas valve terminal designation doesn't make sense either. Normal terminal designation on a honeywell millivolt gas valve is "TH", "TH/PP" and "PP". In your wiring diagram the gas valve terminal designations seem to be incorrect. Also in your diagram, the thermostat does not seem to be connected to anything. Is the toggle switch (on/off ) actually part of what you are calling the "control panel" which on older heaters would consist of the on/off rocker switch and the thermostat? One side of the thermopile/powerpile/pilot generator is normally connected to the "PP" gas valve terminal. The other side of the thermopile would be connected to the "TH/PP" terminal. A second wire attached to the "TH/PP" terminal would then run through all switches, thermostat and safeties back to the "TH" terminal on the gas valve. See attached typical wiring diagram for a millivolt heater. The control circuit disregarding the thermopile is essentially just one series loop between "TH/PP" and "TH".


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Last edited:


Jan 4, 2021

I completely took apart the heater from top to bottom. All the important pieces that I can’t replace seem functional, which I soaked and scrubbed to remove rust. Other than that I replaced most of the parts other that combo valve and the thermostat, both of which there are parts out there for. Yeah I kind of botched my version of wiring diagram and left some things out since I didn’t know how it was supposed to be wired. Your diagram is obviously much better and I will try that configuration later today.
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