Hi. I've got a 2002 Hot Spring prodigy with a heater that fails to stay on. The heater is a No fail 6000. It appears that the small circ pump is working as I can feel it running and the hoses are also buzzing slightly like water is moving. There are no blinking lights to indicate any other error. With the circuit board cover off, the red light for heater on is on when I first turn on the breakers. After a few minute there is a click and the heater on light turns off. I checked the water temp in the spa after a few minutes of running and then measured the thermistor resistance levels, they appear to be slightly above what I think they should be for the ttemp. But as the temp might actuall be different in the tubes they might be close enough?

temp - 89-90
inlet thermistor - ~9.7 Kohm
outlet thermistor - ~8.9 Kohm

Could one of te thermistors be the problem? Any way to bypass or jumper them for testing? Or is there some other problem such as too low a flow? Thanks in advance for helping.

The two things you need to check are:

1. Have you tried resetting the thermal cut-off button? It is located under the 2 lines entering/exiting the heater. It is a small red button and is somewhat concealed under some tape that can be removed. Try pushing it in with a screw driver or something.

2. If that doesn't work then you need to meter-out the heater to see if it is bad.

Make that 3 things...also can check voltage to the heater relay to make sure it is putting out the proper voltage.

The thermistors should only be a tenth or two different in ohms. Secondly, take a close look at the board which the heater wires plug into. Look around the relays and the green colored board, is it burnt?

<<<1>>>

I've tried the heater reset button and it makes no difference. I changed out the thermistors and that also made no difference.

<<<2. If that doesn't work then you need to meter-out the heater to see if it is bad. >>>

What should the heater meter at?

<<<Make>>>

I didn't notice a label for which relay is which, I'll check it. Can the relays be replaced without replacing the entire board?

Thanks,

Ken[/quote]

I can't remembar the exact reading but the heater should give a value like 9.7 or 12.2 ohms or something like that.

The relay to check voltage is the one that the heater wires attach to. If it's bad then you would need to replace that whole left side heater relay board.

Dan,

I checked the voltage at the terminals for the heater and have 246 there while the "heater on" light on the main board is on. After a couple of minutes there's a click and the "heater on" light goes out and the voltage to the heater goes to zero.

I metered the heater and got about 9.8 ohms, so that sounds like it is in the ballpark.

There seems to be flow thru the heater and the silent flow pump is running. If I pull the hose off the outlet there is a pretty good stream of water.

Any other ideas?

Check circ pump flow where it returns to the tub at the fitting that doubles as the drain grille.

The pump can be "running" while not flowing. Be sure your filters are clean as well.

summer timer is engaged, turn it off.

Don't think the heater keeps running for two minutes if summer timer is engaged. The circ pump does, but pretty sure the heater doesn't.

Thanks to all for the replies. I've checked the filters and also tried it briefly without them in place...the heater still trips after a minute or two. There seems to be flow at the drain. As I hadn't really noticed the flow rate before, I have no idea if it is normaly or not. SHouldn't I get some error indication if it trips the heater due to low flow?

I've verified it is not in summer mode.

I've replaced both thermistors as they appeared to be very slightly out of spec. This made no difference. There are no blinking lights or other indicators that something has tripped, other than the heater on light on the main board going out.

As an experiment I bypassed the heater realy board and ran power directly to the heater. The tub seemed to warm up normally.

Any ideas? Is there a way to trouble shoot the ciruit boards? (without just buying & substitution?)

Thanks,

Ken