Halstead Ace High - No heating or hot water

[jaguar49]

Hello,

I have replaced the pcb but no luck.

One of the thermistors at the front has a reading of approx 15 ohms
The thermistor at the back is 0.00 ohms is this a short or is it supposed to be like that ?

Thanks for your help

 

[ianmcd]

obviously if open circuit it is faulty

 

[jaguar49]

Should both thermistors read the same ie approx 15 ohms as one reads 0.00 ie a short

 

[Harry Bloomfield]

The most commonly used thermistors have a resistance of 1K or 10K at 20C, but there are many other values. You check them when not connected to anything else.

 

[Harry Bloomfield]

Should both thermistors read the same ie approx 15 ohms as one reads 0.00 ie a short

No - there are no thermistors which would show zero resistance. Are you sure they are thermistors?

 

[ianmcd]

post a pic of what you are testing

 

[ianmcd]

The most commonly used thermistors have a resistance of 1K or 10K at 20C, but there are many other values. You check them when not connected to anything else.

Harry little bit of useless info for you, if a thermistor staes it is a 12 K for instance , it should measure that at 35 degrees C, as that is body temp so you can hold it in your hand to measure it, no one ever does unless it is a dry pocket one , unless you know what temp the NTC is in the resistance means nothing, but if open circuit obviously faulty

 

[jaguar49]

Could someone kindly point me to a link to " How to drain a halstead ace high boiler " please ?

 

[ianmcd]

The thermistor for the HW and the CH are the same, so just plug the old one that wasnt faulty onto the harness and leave it dangling in mid air, low voltage you wont get a shock, see if the boiler now fires, if it does then it is indeed that thermistor that is faulty

 

[Harry Bloomfield]

Harry little bit of useless info for you, if a thermistor staes it is a 12 K for instance , it should measure that at 35 degrees C, as that is body temp so you can hold it in your hand to measure it, no one ever does unless it is a dry pocket one , unless you know what temp the NTC is in the resistance means nothing, but if open circuit obviously faulty

Yes Ian, I am well aware of that, but thermistor specifications are shown at 20C, room temperature.

The OP said '15 ohms as one reads 0.00 ie a short' - a very low resistance for a thermistor - the opposite of an open circuit.

 

[Gasguru]

They are both bizarre readings...failed thermistors normally go high resistance or open circuit...did the OP measure with the wiring connector disconnected?

 

[jaguar49]

Yes the measurement was across the 2 pins of the thermistor with the plug disconnected.
In order to change it I have to drain the boiler but cannot see where the drain is ??

 

[ianmcd]

just try as I suggested in #9

 

[kidgreen61]

Halstead = skip