SLC250d Heater Problems

[houghtonc79]

Don't know if anyone can help but have recently started having issues with the heater in my SLC. It has single zone air conditioning not climate. The problem started with the passenger side blowing only luke warm air when on full heat and got worse til only cold air comes out. Initially the drivers side was fine but the issue has developed and now the drivers side is only luke warm. Any ideas what this might be as dealer hasn't been much help. Any idea of costs to fix and what parts might be faulty?

 

[Ted]

Sounds like it might be the thermostat.
What temperature does the engine run at?

 

[Jigglyjohnson]

Sure u have hot coolant going into the car ? Split the system into 2 half's
First run to temp and make sure all water pipes are hot the trace back to the bulkhead where they enter the cabin and see if they are hot there if so you need to check the heater pipes inside the car towards the heater matrix to see if hot or not if you have one going in hot and the one coming out is cold that suggests a blockage in the matrix. If you dont have hot pipes at the bulkhead you need to see if you have an online pump sometimes fitted to help aid the circulation of the coolant if you have test it to see if it is working. Failing that are you sure the ac panel is working correctly and making the blend flaps in the heater unit give you hot air ?

 

[houghtonc79]

Sounds like it might be the thermostat.
What temperature does the engine run at?

The engine is running at normal temp around 90 degrees

 

[houghtonc79]

Sure u have hot coolant going into the car ? Split the system into 2 half's
First run to temp and make sure all water pipes are hot the trace back to the bulkhead where they enter the cabin and see if they are hot there if so you need to check the heater pipes inside the car towards the heater matrix to see if hot or not if you have one going in hot and the one coming out is cold that suggests a blockage in the matrix. If you dont have hot pipes at the bulkhead you need to see if you have an online pump sometimes fitted to help aid the circulation of the coolant if you have test it to see if it is working. Failing that are you sure the ac panel is working correctly and making the blend flaps in the heater unit give you hot air ?

Thanks, I'm only average tech ability but it was the fact the problem started slightly on the passenger side then got worse then moved onto the drivers side too. I now get slightly warm air on the drivers side but nowhere near as hot as it should be. I'm tempted to think your suggestion about the blending is the most likely but don't know why it's sort of been a contagious problem!!