I returned from vacation to find a blown 10A fuse (which I replaced) and OH on the topside panel. Replaced the temp sensor which resolved the OH indicator. Still no heat. Pump runs fine. 220v going into the heater relay, but nothing coming out. Blower relay is clicking, which it did not do before. Any sense of what is going on here? Is there no elec to the heater element because of a bad/blown heater relay, or is it that the relay isn't being "told" to heat? thanks!

Have no idea. Need more info on your system make/model etc.

This is an in-ground spa that I built in 2004 using a Pinnacle Controller (circuit board by Balboa - 2000LE Std). We have a 110V Hayward pump used to circulate the water (hooked up as the low-speed pump). There's no blower.

Everything was working beautifully for over two years. We returned from vacation and found a cold tub and "OH" on the top-side readout. The probe thought the water temp was over 110F, but it was really 65F. I replaced the probe (flow temp, not hi-limit) and that seemed to resolve the temp problem. But there was still no heat.

Further examination revealed a blown 10A fuse that is labeled F7 on the board and is near the "ozone" relay. We don't have any ozone device. I replaced the fuse, which had no effect on the temp problem. The new fuse also did not have any effect on a clicking relay, which is labeled on the board as the blower. The topside panel light indicates that Pump 2 is active, and seems directly related to the clicking relay. Never had this issue before.

I checked all electrical connections for amperage and voltage. There is 220V going into the heater relay, and no voltage coming out. No power going to the heater element.

Does that additional info help? Any thoughts? Thanks.

Sounds like a bad system board. Possibly hit by a surge or lightning strike. The blown 10 amp fuse is usually reserved for a blower.

Look for the number inside the controller somewhere: 52295 or something close then post back what you find.

AH.. now that you mention "surge", it occurs to me that the air conditioner experienced an arc when a wire wore thin and made contact with the junction box. The whole thing blew. Not on the same circuit, but fed from the same subpanel. Maybe related?

I'll look for the controller number and post back. thanks again.

It says 52295

This should take care of it.

http://spapartsnet.com/Reference-Catalog/Spa-Packs-and-Controls/Circuit-Board-Balboa-2000LE_3298_0_1.html

Be sure you take digital photos of the wiring etc prior to r/r of the board.

I replaced the entire system board and the situation is exactly as before. There is no heat and the controller is not turning the pump off after 2 hours, which is normal. It's got to be the heater relay, right?

Check your pressure switch on the heater.

The cpu on the board is what controls the 'heater relay' among others, and if it doesn't receive the proper signal inputs (temp and overlimit sensor and pressure switch), the heater relay will never turn on.

Is the "pressure switch" the same thing as the flow switch on the heater element? On the heater there is a circular device that (I believe) monitors the flow of water to ensure there is sufficient pressure, or flow. Removing one of the contacts (either red or black) creates a click on the controller board, but has no effect on the heating. So there seems to be power going to the switch, but I'm not sure how to "test" the switch. I turned the adjustable thumbscrew and made sure it wasn't sticking. But I can't vouch for the internal mechanism.