I have above bmw that I get my intermittently no heating or have to turn temp up to 24 to get a bit of heat , apart from taking to garage any ideas what it can be please or what I can do to diagnose the issue. The engine does not overheat and the temp stays in the middle. Coolant is ok have to top up a small amount between min an max sometimes.

Thanks

This could get complicated....

It could be...

1. Problem with HVAC controller or air-mix flap servo motor (one or two motors depending on variant fitted).

2. Faulty temp sensor on heat exchanger.

3. Fault of electric water valve, or wiring to it etc.

4. Blocked heat exchanger.

With the engine hot and running (coolant above 80deg. C) set the heater to max temp and feel the pipes to the heat exchanger (matrix) and check their temp is at least 65 deg C. If they aren't then you have a flow problem. If they are hot enough but heater output is low then you likely have a problem with HVAC controller and/or mix flaps. Really you'd need a dealer or specialist to accurately diagnose and fix. Be prepared for some serious expenditure! Make sure you check coolant carefully. These 1.5L 3-cyl engines have started to get a reputation for head gasket failure..... Its a fully sealed cooling system and and should not lose any coolant - topping up should very very seldom be required...

Edited by Rerepo on 21/05/2024 at 02:58