Cruiseair Thermistor

[JLR]

The AC in the VIP stateroom works fine but the thermistor is not working properly. It thinks it is down to 64 degrees when the temp is really 68 degrees etc. Therefore, it shuts down the compressor prematurely. When I had the AC fellow on the boat to check it out, he said it was likely the thermistor which, as I understand it, is the little temperature probe connected by two wires to the compressor. He also said that he could not get them anymore and that I would need to upgrade to a newer style which required a more significant job re to rewire. Does anyone know where I can can get the ("old style") temperature probe? As I recall it is just a simple two wire connection that I can cut and splice for the replacement. Thanks.

 

[Reefgeorge]

The AC in the VIP stateroom works fine but the thermistor is not working properly. It thinks it is down to 64 degrees when the temp is really 68 degrees etc. Therefore, it shuts down the compressor prematurely. When I had the AC fellow on the boat to check it out, he said it was likely the thermistor which, as I understand it, is the little temperature probe connected by two wires to the compressor. He also said that he could not get them anymore and that I would need to upgrade to a newer style which required a more significant job re to rewire. Does anyone know where I can can get the ("old style") temperature probe? As I recall it is just a simple two wire connection that I can cut and splice for the replacement. Thanks.

1) if the probe is connected to the condenser unit with a phone jack, check the connector for corrosion.

2) There may be a programming step that you can perform at the indoor controller to calibrate the temperature reading of the probe.

3) If 1/2 don't work, can you supply a picture of the probe and the model of the AC unit?

 

[JLR]

Will give it a shot this weekend. I do not think it is connected by a telephone type connector. But, I'll check and see.

 

[Reefgeorge]

By way of example, the Cruisair SMXII control calibrates the temperature sensor by hitting:

Off

Set/Up together

Use up/down keys to adjust temp display reading

 

[Milacron]

The AC in the VIP stateroom works fine but the thermistor is not working properly. It thinks it is down to 64 degrees when the temp is really 68 degrees etc. Therefore, it shuts down the compressor prematurely. When I had the AC fellow on the boat to check it out, he said it was likely the thermistor which, as I understand it, is the little temperature probe connected by two wires to the compressor. He also said that he could not get them anymore and that I would need to upgrade to a newer style which required a more significant job re to rewire. Does anyone know where I can can get the ("old style") temperature probe? As I recall it is just a simple two wire connection that I can cut and splice for the replacement. Thanks.

The only thing connected to the compressor is the voltage to run it and an overheat sensor. Maybe you mean the condenser, which the compressor is part of.

But assuming you have typical SMX digital control thermostat, the temp sensor is monitored by the thermostat, not the condenser. So do you mean the tiny temp sensor capillary tube bulb is the culprit ? If so, is it located at the incoming air filter as it should be ? And make sure that bulb didn't get painted or is touching metal on the condenser. If the temp bulb is in the right place I would tend to suspect the SMX programming as George mentioned or something gone wrong in the SMX thermostat itself.

 

[JLR]

Thanks. I'll check the bulb and make sure it is in the right place. I would have been looking in the return vent not the incoming vent. Very helpful.

 

[Milacron]

Correction of typo on my part...assuming the usual split system ....temp bulb not touching air handler (or cooling unit, as Cruisair calls it) rather than condenser

 

[JLR]

Checked yesterday. It is a little red bulb like thing with two wires leading to it. It is not touching anything metal nor has it been painted.

 

[Milacron]

Checked yesterday. It is a little red bulb like thing with two wires leading to it. It is not touching anything metal nor has it been painted.

yeah, that's it. So what exactly is your thermostat control...SMX I, II, or one of the old style with turn knobs ? I suppose the little bulb could go bad...hard to believe Cruisair can't supply these any more...I'd call them direct to see...their Richmond, VA location has been more helpful to me than the FL location.

 

[Reefgeorge]

yeah, that's it. So what exactly is your thermostat control...SMX I, II, or one of the old style with turn knobs ? I suppose the little bulb could go bad...hard to believe Cruisair can't supply these any more...I'd call them direct to see...their Richmond, VA location has been more helpful to me than the FL location.

What Milacron said.

In order to help you find a fix, we need to know as many part numbers as possible (controller, evaporator, condensing unit). Also, can you supply a picture of the temp probe/thermistor and your controller (wall unit with knobs or buttons)? Depending on how much this temp accuracy problem is bothering you, it can be solved. If you cannot calibrate the reading as suggested above then there are 3 choices. 1) Determine the probe part number and find it on the internet. I have put things in an eBay search that have been discontinued for a decade and found one for sale a year later. 2) Remember that a cabin temp of 78F is a setting of 74F and live with it. 3) Characterize the temp probe (temp vs resistance) and splice in a replacement generic thermistor with the same characteristics.

When your guy suggested an "upgrade", what was he referring to?

 

[JLR]

Thanks all for the help. I have the newer style SMX displays. It is digital and not the three knob style. As between the two newer displays, in the VIP I have the older style, I think. It seems to me that with a simple two wire splice, I should be able to swap it out. I'll call Richmond once I can get more precise information.

 

[Milacron]

Thanks all for the help. I have the newer style SMX displays. It is digital and not the three knob style. As between the two newer displays, in the VIP I have the older style, I think. It seems to me that with a simple two wire splice, I should be able to swap it out. I'll call Richmond once I can get more precise information.

Call 954-973-2477....which is Florida number but ask to be transferred to Richmond and ask for service. I have a name but reluctant to post it on the web for fear he might get inundated with calls but you could pm me for name if necessary.

As I suspected they do have the thermister bulb, part is TSEP-X...with X being wire length. But you can order TSEP-5 (least expensive one) and simply splice in into existing wires.

Having said all that, he says when those go bad usually there is more range between numbers than you describe, so the SMX programming or SMX board itself is more suspect from your description.

 

[JLR]

Thank you.

 

[JLR]

Spoke to Richmond. They suggest the following in the following order. First., move the sensor. Second, if that doesn't work, check for corrosion on the splices near the sensor. Third, if both of the above do not work, buy a new sensor and splice it in. I will report back when I have an answer. Thanks.