I have a Coleman 1993 Horizon 400 Series spa. 230v circuit, Powerworks 2 model # 4080 Slate MBL control. Balboa circiut board Model 400 CA. Electronic type topside controls. 2- 230v jet pumps. 2" ss flow through heater 15" long. OH shows constantly. I'm not sure if the spa actually overheated or not. After powering up the keypad readout goes 5,4,3,2,1,0, OH. The OH stays on and the keypad is disabled. Power on and off just repeats the process. Water is cold, water level correct. Spa was working perfect for 3 years since installation of new board and heater. Thanks for the forum and the opportunity to participate, Linny

First thing to do is at a minimum, replace the hi-limit sensor.

This:
http://spapartsnet.com/Electronic-Temp- ... 1_1_1.html
or better yet:
http://spapartsnet.com/Electronic-Temp- ... 6_1_1.html

If that doesn't help, then you'll need to replace the circuit board.

Pageup, thanks for the quick reply. The hi-limit sensors didn't fix the problem and I'll need to order a cicuit board but I can't figure out which one to get. Is there a # on it somewhere? Can you tell which one I need from the spa model# or from the pictures? Linny

sent you an email.

The # on that chip is 400R2A. I don't know if you recieved my e-mail reply or not. Maybe you have'nt had a chance to get to it. I'll post it here just in case. Thanks, Linny