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Mitsibushi Ecodan U4 error code: thermistor values

 
Air Source Heat Pumps (ASHPs)
Last Post by hughes674 2 years ago
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 hughes674
(@hughes674)
New Member Member
Joined: 2 years ago
Posts: 4
Topic starter 28/07/2024 10:06 am   [#1637]

Hi All

Have had the pleasure of a trouble free air source heat pump for 8 years.

Came on today with a U4 error code and tripped the RCCB. The manual states that the error refers to one of the thermistors in the outdoor unit (TH32,TH33,TH6,TH7 or TH8). 

The Heat pump is a Mitsibushi Ecodan PUHZ-W85VHA2R1-BS UK

Would anyone know where I can get the resistance values for the thermistors to check which one is faulty?

Thanks in advance.



   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4763
28/07/2024 10:30 am  

Welcome to the forums @hughes674 – the resistance values you're looking for are available in the ME Engineer app.

ME Engineer App

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 hughes674
(@hughes674)
New Member Member
Joined: 2 years ago
Posts: 4
Topic starter 28/07/2024 12:20 pm  

@editor Hi

Thank you. Appreciated.

Bad news checked all the thermistors apart from TH8 as cant get to it and they all are within range.

Got a feeling its gonna be expensive.



   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4763
28/07/2024 12:22 pm  

And here's a suggestion from Mitsubishi's Technical Trainer. This video shows how to use the Main Remote Controller to look at thermistor readings, which can help narrow down which thermistor needs testing.


New to heat pumps? Take the Heat Pump Fundamentals course and use INTRO50 at checkout for 50% off.
Rewritten and updated for 2027
📘 From Zero to Heat Pump Hero
🛠️ Bodge Buster
🎧 Prefer to listen? Heat Pumps Explained


   
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 hughes674
(@hughes674)
New Member Member
Joined: 2 years ago
Posts: 4
Topic starter 28/07/2024 12:51 pm  

@editor Thank you.

All the thermistor temperature readings look right but not displaying anything for TH8.

Is there a way of the controller telling me which thermistor is faulty? 



   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4763
28/07/2024 9:42 pm  

@hughes674 so the technical trainer has informed me that if have melcloud installed you can call the technical help desk and they will be able to access the system remotely and provide further guidance. If not, it’s a case of getting an engineer out unfortunately.


New to heat pumps? Take the Heat Pump Fundamentals course and use INTRO50 at checkout for 50% off.
Rewritten and updated for 2027
📘 From Zero to Heat Pump Hero
🛠️ Bodge Buster
🎧 Prefer to listen? Heat Pumps Explained


   
ReplyQuote
 hughes674
(@hughes674)
New Member Member
Joined: 2 years ago
Posts: 4
Topic starter 28/09/2024 11:38 am  

Hi All

Mitsubishi Ecodan PUHZ-W85VHA2R1-BS UK

Following on from a U4 fault on my heat pump I have now finally received the TH8 thermistor from Mitsubishi.

Issue I have is the power board needs removing to replace it but cannot get the power board off. released the rubber clips but the board is still firmly attached somehow. 

Has anyone had any experience removing these? 



   
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