Pina59 Posted July 16, 2021 Report Share Posted July 16, 2021 Just trying to get to the bottom of a recurring HL fault on a Hydroquip CS7500 spa pack. The fault kicks in when there is a power cut or if the tub is restarted when the water is warm. Flushing the tub and refilling seems to resolve the issue which is bizzare. My first port of call was replacing the HL sensor which doesn't seem to have fixed the issue. I've also replaced the topside control which was faulty. My understanding of the system is that the HL sensor is what will initiate the code. Is there any benefit in replacing the temperature probe? Water flow seems good (have tried running without the filter to see if there were issues there), and heater does not feel hot to the touch when the code is getting thrown. My only other thought is that there is a fault with the PCB but I'd like to avoid having to replace this if I can even try and diagnose which relay (I'm suspecting a relay) is faulty. Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted July 16, 2021 Report Share Posted July 16, 2021 5 hours ago, Pina59 said: fault kicks in when there is a power cut If the heater is heating and power is turned off the residual heat in the heater is no longer carried away by the water flow and will overheat the sensor at the heater. Is there another issue? This is normal operation. 1 Quote Link to comment Share on other sites More sharing options...
Pina59 Posted July 16, 2021 Author Report Share Posted July 16, 2021 Thanks, hadn't thought about that. With the CS7500, faults are supposed to clear when the spa pack is restarted. This doesn't seem to be happening so likely a sticking relay? Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted July 16, 2021 Report Share Posted July 16, 2021 If the heater is still hot when you turn it back on you will still get the error. An overheat error can be caused by many things, from dirty filters to faulty circuit boards. Post some pics of the circuit board, wiring diagram, and equipment area so we can see what you have. 1 Quote Link to comment Share on other sites More sharing options...
Pina59 Posted July 19, 2021 Author Report Share Posted July 19, 2021 ItI've left the spa to cool down properly and still getting a HL fault. The relays go a bit nuts when starting up (lots of clicking) which seems odd. Both the HL (new) sensor and older temperature sensor appear to be giving reliable resistivity readings when tested. I've added some photos of the pack and board. Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted July 20, 2021 Report Share Posted July 20, 2021 6 hours ago, Pina59 said: appear to be giving reliable resistivity readings when tested. Be specific. What readings, exactly? On 7/16/2021 at 4:26 PM, RDspaguy said: Post some pics of the circuit board, wiring diagram, and equipment area so we can see what you have. Also the stickers on top of the box. I am not familiar with this pack, but rapid relay clicking is usually a low voltage/control (transformer/board) issue or incoming power issue. Check incoming power, those tape wrapped connections look like a great place to have a voltage drop. Next check the voltage at the light, if you can get it to turn on. I see 3 sensors on that board, one labelled "dry detect". What is the dry detect? If it is a temp probe (thermistor), what are the other 2? Quote Link to comment Share on other sites More sharing options...
Pina59 Posted July 20, 2021 Author Report Share Posted July 20, 2021 I'm getting ~10,000 ohms for the two temperature sensors which is consistent with the measured temperature using an external thermometer (https://spacare.com/SensorResistanceValuesForHydroQuipandGecko.aspx) The dry detect is for the flow sensor. The one adjacent is the thermistor and the 2 cabled one is the HL sensor. When you say check the light, presumably you mean SPA light rather than the heater light? The two tapped connections (arguably not very tidy looking!) are just tape around a cube connector for the cables so there is a solid connection there. It's maybe worth pointing out that I'm in europe so on 240V. As an update, the spa has started again this morning and the HL fault has cleared. It's taken a while to get back to this point (circa 2 weeks) which makes me think there's something intermittent somewhere on the board. 1 Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted July 20, 2021 Report Share Posted July 20, 2021 5 hours ago, Pina59 said: ~10,000 ohms Not nearly precise enough, as I am looking for a difference of hundreds of ohms. There is only so much I can do from here. Get accurate ohm readings to determine if a sensor is bad. Test the pressure switch for proper function (open when pump off, closed when pump on). Check for flow issues from a faulty pump, dirty filter, or other flow restriction. Test heater relay function (turns on and off when it should). Quote Link to comment Share on other sites More sharing options...
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