R171 heaters intermittent

[cps13]

Hi

My wife’s SLK (2012 250) has a weird fault with the heaters. You can turn the car on, and they blow cold even when set to max heat, drive around for 10-15mins and still cold. Turn the engine off, and straight back on and then they blow hot.

Any ideas?

[wild rover]

Engine coolant running at the right temperature?
If not may require a new thermostat.
Heater fan working intermittently.
Best of luck

[trevalvole]

A 2012 250 will be a R172, I think.

[595Heaven]

I’d take a look at the SLK forum www.slkworld.com - loads of tech resources on there

[Dog Star]

Stick duo valve?

[Huzzah]

Dog Star said:

Stick duo valve?

This would be my guess too.

[cps13]

So, after a couple of weeks of tampering… I think it was an issue with a low auxiliary battery. Charged the battery and it is now working fine.

Might be coincidence, but was having a few other strange happenings such as random beeps when turning the ignition on which never happened before. Audio controls on the steering wheel not working. Roof intermittently not working.

Charged the battery and they’ve all gone.

[595Heaven]

Glad it is sorted - mine used to hate a low battery and threw all sorts of errors.

In the end I think the drain was from a dormant Tracker which I removed. It had NiCad batteries inside but suspect they were long dead so it was always drawing some current.