Notifications

Clear all

Ecodan U4 error code

spacebiscuit · 2024-06-12T22:44:14Z

Hi all, I have an 11 year old Mitsubishi Ecodan that is showing a U4 error code on the control panel. I’ve looked up the error code: Open or close circuit Ecodan thermistors (TH3, TH32, TH33, TH6, TH7, TH8) – open or close circuit or disconnected from main board. Does this require a straight swap out of the main power baord? Thanks in advance.

Page 2 / 2 Prev

Air Source Heat Pumps (ASHPs)

Last Post by spacebiscuit 1 year ago

18 Posts

4 Users

4 Reactions

3,503 Views

RSS

spacebiscuit

(@spacebiscuit)

Eminent Member Member

Joined: 1 year ago

Posts: 11

Topic starter 17/06/2024 1:42 pm

I've cleaned that solder joint up and resoldered it, looks good now. But today no matter what I've tried the machine will not spin up. I've tried wiggling the wires connectors, thermistors on the pipes but nothing! I'm all out of ideas.

ReplyQuote

spacebiscuit

(@spacebiscuit)

Eminent Member Member

Joined: 1 year ago

Posts: 11

Topic starter 18/06/2024 10:17 am

I discovered that there are some dip switches (SW2) that can be set on the unit's controller board which will indicate the exact thermistor at fault. In my case it was the water inlet thermistor that was showing a wrong resistance which I missed when I was testing each thermistor for general operation not actual readings.

Part ordered and hopefully that will be it fixed!

👍

ReplyQuote

Gary

(@gary)

Prominent Member Member

Joined: 3 years ago

Posts: 350

18/06/2024 11:58 am

@spacebiscuit could you detail what switches you changed maybe useful for someone else in the future thanks

ReplyQuote

spacebiscuit

(@spacebiscuit)

Eminent Member Member

Joined: 1 year ago

Posts: 11

Topic starter 18/06/2024 1:25 pm

On SW2 switches 1, 4 and 6 need to be on - this will then return a number corresponding to a thermistor. Although in my case it returned '3' which could be one of two. So I then had to try 3,4,5 on which gives the temperature of the inlet - mine was read '102' which is not achievable and so indicates a bad resistance reading and therefore TH32 being the faulty thermistor - I hope!

See pages 74 and 76 here:

RENEWABLEENERGYHUB.CO.UK "https://www.renewableenergyhub.co.uk/uploads/products/1628/product_brochures/Ecodan_ATW_PUHZ-HW140VHA2-BS-PUHZ-HW140YHA2-BS_Service.pdf"

This post was modified 1 year ago by spacebiscuit

👍

ReplyQuote

Derek M

(@derek-m)

Illustrious Member Member

Joined: 5 years ago

Posts: 4427

18/06/2024 2:06 pm

@spacebiscuit

Page 55 shows the resistance range for TH32, which could be measured if you have a suitable multimeter. You could also test the circuit board by connecting a suitable resistor in place of the thermistor.

ReplyQuote

spacebiscuit

(@spacebiscuit)

Eminent Member Member

Joined: 1 year ago

Posts: 11