Control Pad Driving Me Crazy

[IBinit4fun]

Haven't been around lately, but this forum helped me pick my tub in 2004. Need help again. Abbreviated for character count limit.
Have 2003 Marquis Euphoria. Balboa MTS2KU Control. 220 Volts. 2 motors. No recirc pump. I replaced locked up motor- one that pumps H2O through heater, then half the jets. Bought AO Smith motor from local reputable electric shop. They sized motor based on old motor, resealed, mounted pump on motor. Same HP, 2 spd, amps, frame. I installed motor/pump in tub, but motor wouldn't start in low speed, just hummed. Got OHH (overheat) & Dr (no flow) error because motor didn't start on low speed when heat was called for. H2O was still cold. Returned motor. Faulty starter capacitor switch. They fixed, I reinstalled. Spa heated to set temp & ran perfect 1 day before problems below started. I assume new motor is not related, but not sure. Both motors still running fine on both speeds.
After a day of normal running, noticed the control pad heater light was lit with no pump running. But I got no errors & the H2O was at set temp (per bulb thermometer). Other than heater light staying on, tub worked fine. However, main ctrl pad button that turns on pumps quit working. Had to use aux pad to start pumps. Thought maybe a short in the main ctrl pad was causing pump button not to work & heater light to stay on. They're next to each other on pad. Turned off power, then back on. Heard relay click & heater light came on dim. Heard another click & heater light flickered for a while. Then heater light came on bright. Did this for a few days, but tub otherwise worked fine. It would heat to whatever temp I set. All other buttons on the ctrl pad worked & speeds & timers worked fine. Cleaning cycle, temp checking cycle, etc. all worked as they should. After a while, heater light came on bright & has stayed on bright ever since.
After a day of this, removed cover from control box. Relays were 2 hi-temp, 1 heater, 2 low pump, 2 hi pump, & 1 game. Don't know what game relay is. 2 hi-temp relays were closed when power on, open when power to tub was off. All pump relays properly opened & closed as the 2 motors came on & off. The heater relay was open when the H2O temp reached the setting on the ctrl pad & closed when the H2O temp fell below the setting on the ctrl pad. The relay also closed when I increased the ctrl pad temp setting higher than the H2O temp & opened when I lowered the ctrl pad temp setting lower than the H2O temp. The low speed pump relay would close & pump for heater tube would run on low speed when heater relay closed. When H2O reached the set temp, heater & low pump relays would open & pump shut off. This all seemed normal, except that heater light was staying on all the time & main ctrl pad pump button would not work. I then put my volt meter between incoming neutral white wire & one leg on heater element right where it goes into heater tube. It read 120 volts. I did same for other heater element leg & it also read 120 volts. However, both legs read 120 volts all the time, regardless of whether heater relay is open or closed. If there is a contactor, I didn't see it. I thought maybe if there was a short in the ctrl pad, it might somehow be leaking back & causing voltage to show at heater element legs. So I turned off tub & unplugged cable that goes to ctrl pad. I powered tub & checked voltage at heater element legs again. Both read 120 volts, but heater relay was open. I turned off power, reconnected ctrl pad, re-powered, & raised temp setting on ctrl pad above H2O temp. I checked voltage before & after raising setting & both times read 120 volts on each leg. Bottom line is that heater element was receiving 120 volts on each leg, regardless of H2O temp, ctrl pad settings, or heater relay position.
With 120 volts on each leg & no pump running, I wondered why I would not be getting an OHH or Dr error. I reasoned that the chip logic must be to issue an error only if the heater relay is closed & no circulation was taking place. I further reasoned that if I left as is, it may cause an actual overheat with no error message. I thought I'd test my theory by starting the pumps on low speed & see if the H2O temp would keep getting hotter, since there was 120 volts on each leg of heater all the time.
I turned pumps on low speed at aux pad. After about two minutes, tub went crazy. Both pumps shut off after about two minutes, came back on high speed, shut back off, kept cycling on & off, ctrl pad display flashed on & off, finally went out & stayed out, all buttons on main ctrl pad stopped working. Turned power off to tub. Turned power back on. After normal 4 minute prime delay, low speed motor that pumps H2O through heater tube came on low like it is in heat cycle. Nothing on main ctrl pad or aux pad worked, except heater light was still on bright. I am guessing the aux pad is wired to main ctrl pad, because only one ctrl pad cable plugs into control box. Heater light was still on bright, but heater relay was open. I shut off tub. My thoughts are a bad ctrl pad sending crazy signals. But if true, what I don't understand is why there was 120 volts to each leg of heater element when I had the ctrl pad unplugged & heater relay was open. I thought about buying ctrl pad, but fear that if problem is main board, it might fry new ctrl pad. I am very close to calling repairman, but thought I'd put it out here before giving up. All help is appreciated.

[Chas]

I sure don't consider calling a repair man "giving up."

I would also check your wiring carefully.

HTH

 

[IBinit4fun]

Thanks for the feeedback. I didn't change any wiring, but did confirm that all is correct and tight. Let me reduce my original post to an easier and short question. Is it normal for there to be 120 volts on each leg of a 220 heater coil when the heater relay is open? If someone can explain why, then I would assume my control pad has shorted out and is sending erratic messages to the control box. Thanks.

[Dr. Spa™ Ret.]

If you're measuring the voltage from one leg to ground (a COMPLETELY wrong way to test 220v), then it could be normal. If the heater coil is only cutting power to one leg of power going to the heater, electricity would simple be traveling down the still hot leg, through the heater element, and is readable on the side you "think" should be dead.

[IBinit4fun]

Thanks, Dr Spa. I am checking voltage by putting one probe on the white neutral wire and the other probe on one leg of the heater element. I repeat the procedure for the other leg. If I were to check from heater to ground, it would trip the GFCI. Both legs read 110 volts all the time, regardless if heater relay is open or closed. I just don't know if this is normal. It doesn't seem to me that there should be any voltage on either leg of the heater when the heat relay is open. I would think that would cause the tub to overheat, but it doesn't. Maybe I am still measuring it wrong. My late dad was an electrician and I remember that he checked 220 volts by putting one probe on one leg and the other probe on the other. When I tried that, it tripped the GFCI. I'll surf the internet to see how I shold be checking. Thanks again. Any other advice?

[IBinit4fun]

Thanks for the help. I talked to an electrician yesterday and got my question answered. I thought I'd share here in case it might help someone else down the road. My question in reference to a 220 volt tub was if there should be 120 volts on each leg of the heating element when the heater relay is open. The answer is yes. The reason is that a 220 circuit has no return (neutral) wire, but rather there is 110 volts applied to each leg of the heater element. Grossly oversimplified and avoiding a discussion of alternating current sin waves and 180 degrees out of phase, this means that both 110 volt leads are required to complete the 220 circuit and have amps flow. The heater relay makes or breaks the connection to one of the two 110 volt inputs, thus making or breaking the 220 circuit. When I checked voltage with the heater relay open, I completed a 110 volt circuit with my volt meter by touching one lead to the incoming white neutral wire and the other to one leg of the heater element. With the heater relay open, the heater element was just acting like a wire, so it didn't matter which leg I touched with the meter, I'd still get the 110 volt reading from the non-heater relay 110 volt input. I'm now convinced that my probelm is the topside heater control panel and will order one today. I'll post if that fixed the problem.