Failure Code 597, temp only 75 C

[Acond]

Hello

Astra J 2010 1.6 has servivce light on. Can be reseted by Menu button but comes back after 10 minutes. Code reader gives code 597 - related obviously to thermostat. Engine temp does not come higher than 75C, normally about 90C.  Both upper and lower cooler hoses are warm but not hot. Heater and ac works normally (blowing warm air). Runs smoothly all seems to be OK. Please help whether this is typical failure and where to start to fix it. Does this engine have electrical controlled/heated thermostat? Sticking. Please help

[Rusty2009]

I would say possibly thermostat but what code reader are you using as 597 could be anything and isn't even a proper code.

[Acond]

OP-Com
Code is P0597, think a proper one, stat heater circuit malfunction
https://www.autocodes.com/p0597.html

[Rusty2009]

https://workshop-manuals.com/vauxhall/as...597-p0599/

[Acond]

Thanks for good link with instructions how to test. Forgot to inform that in the meantime I measured the resistance of the heater unit in top of stat cover and found it is about 18 Ohms when Service Light is not illuminating (engine cold). When I drive the engine warm and Service Light start to illuminate resistance climbed higher than 4 Mega Ohms - practically open circuit. This made me think that need to change the thermostat assembly. Already ordered the part. Hope this was right decision. I repeated the test several times. When engine cold no light and low resistance, after ten minutes when engine getting warm light illuminates and high resistance. When engine hot and I put the ignition on the service light starts to illuminate within e.g. 10 seconds, when engine cold I did not wait more than 1 minute but the light did not come on. This 18 ohms correlates pretty well with this link below. Really hope I made a right diagnosis. Can be of course control module K20 problem with this code or any wire/connector failure but let's see. I report my findings after having changed the thermostat ass.


https://www.youtube.com/watch?reload=9&v=mk020n9-SPk

[Acond]

Hello

New stat + housing installed. Service light not illuminating anymore, hope this was the case this time. difficult to bleed before I found the cap in top of radiator. Found that also fan (cooler) stopped to run in full speed now, perhaps something to do with this.