Spa not heating on low pump setting

[ac_bc]

Hi, hoping to get some help with troubleshooting this issue. I have an issue with my spa/hot tub not heating properly.

It appears to be heating properly when high pump mode is engaged - reaches and actually exceeds set temp (and will keep going up if you don't stop it). However on no pump or low pump mode, it never reaches the set heat (right now I'm trying to set it at 95-97F as we have young kids, but it will only reach 92-94F). It's quite cold right now so on those modes it loses heat fairly quickly if we're using it, or slowly if covered/not in use, but it doesn't drop below ~92F, indicating it seems to be getting some heat. The heater element tube is indeed warm and the heating LED does come on correctly when set temp has not been reached (requesting heating). No error codes present.

I have done a number of things to troubleshoot. It's a Gecko S-Class type spa, made in about 2003. I replaced the heating element as the old one shorted recently, about 2 months ago. Everything was working fine once it was replaced until recently. New element is generating heat at times obviously so I don't suspect an issue with it. Voltage is ~240V across terminals. I investigated the pressure switch pretty thoroughly - pulled off leads and tested with multimeter, reading ~1 ohm, but getting proper continuity (buzzing on tester) for both low and high pump modes. Jumping/shorting the pressure switch leads did not fix the problem (tried this for an hour or so and it did not appear to be heating as it normally should on low pump mode). I am thinking of replacing pressure switch as it is obviously very old and never replaced as far as I know, and could maybe be momentarily cutting out during low pump mode.

Temperature gauge seems OK as it appears to read correct temperature, and I verified water temp with an digital thermometer and they read the same. No error codes to indicate a flow issue - I thoroughly checked filter area for obstructions and filter is clean. Possible obstructions somewhere within the system?

Appears to be no flow issues - pumps still pump out solid water pressure through jets, and can feel water flow in both low and high pump modes.

Thoughts on what to try next?

[CanadianSpaTech]

1st remove the filters until the issue is fixed. Remove the from the equation. New used just cleaned or otherwise. Remove them.

Do you have a multi meter and knowledge of its use?

Do you get 3 little dots on the topside display?

If it will heat in high speed but not low to me that indicates a flow issue. The pressure switch needs the extra flow to work. It might need to be replaced or adjusted. If it works after adjustment I would replace it next chance I get. Dirty filters are the cause of most flow errors. Anytime you have any issue with your spa always remove the filters and rest the breaker and see if it works. 

 

Gecko S-Class Tech Manual Here: https://issuu.com/geckomkt/docs/sc_cf_ce_as_service_manual_en

 

When you installed the new heater element did you look down the heater tube after it was installed and ensure that the element was not touching the side wall of the heater tube? If it is touching it will hot spot against the tube and have a short life.

Link to Gekco TV. Other helpful testing videos there:

 

 

[Cusser]

15 hours ago, CanadianSpaTech said:

If it will heat in high speed but not low to me that indicates a flow issue. The pressure switch needs the extra flow to work. It might need to be replaced or adjusted. If it works after adjustment I would replace it next chance I get. Dirty filters are the cause of most flow errors. Anytime you have any issue with your spa always remove the filters and rest the breaker and see if it works.

 

 

I was also thinking pressure switch-related issue as stated above.  Sorry, could not make the video NOT show.

[ac_bc]

Hi, thanks for the advice and replies. We used the tub last night, getting it to temp by running the pump on high. It was at ~97F. I left it overnight set to 96F (and pumps, etc on auto) but it has dropped to 91F. The filter is quite old so I have removed it for now and will see if it that works to get it to heat on normal mode.

Yes I have a multimeter and am familiar with how to use it, electronics, etc.

I will do some further testing on the pressure switch. I have set it so very little PSI is required to close it, and in my previous testing/jumping it didn't appear to be the cause, but I will further test it's open and closed resistance. Closed resistance did seem a little high (~1.7 ohm) but my multimeter is a bit out of calibration I think (reading 0.8-0.9 ohm when leads are shorted).

Curiously, I did test the heater element with the leads disconnected yesterday, and I am getting an OL / open circuit reading on the multimeter. This is strange as I expected the normal ~9-14 ohm reading. I confirmed my multimeter is fine by testing a 10-ohm resistor I had on hand, which tested perfectly (10.2-10.3 ohm). I am getting 249V when it is connected and calling for heat. I don't understand how I'm not getting a resistance reading when I know the heater element is at least working partially (still heating when pump is on high).

I think my next step after filterless testing will be to disconnect the heater element, check for air/obstructions and see if heater element is touching pipe wall like suggested.

Thanks!

[RDspaguy]

The pump running on high speed will heat the water some. If you have no continuity on the heater it is bad. 

[Barry Buenvenida]

I had no voltage to my heater when spa was on low speed but when I set the spa to a higher temp and the spa kicked on to high speed the heater received voltage....indicating a bad circut board??.

.heater is good...motor is good ..no codes.

[CanadianSpaTech]

@Barry Buenvenidaplease start your own post. Post a photo of your circuit board and the schematic on the inside cover if there is one.