Heating - fan - aircon behaviour, is this normal?

[bin]

Hi
I'm a lot puzzled about the way my ventilation system is behaving and wonder if this makes sense to anyone.
The car is a 1998/9 C200 W202 20k miles - fan dial on left, direction on the right with Rest and EC button in the middle. Air-con re-gassed by Indy but problem existed before.

I prefer to run with EC off - i.e. the red light in the EC button should be ON.
However, after starting the car the light is OFF for a period of time. This period does not seem to be affected by outside heat, but on the last few cold mornings it has stayed off longer - say about 20 minutes as opposed to around 10 normally. After that the light flickers on, and then the fan comes on - even though it is set to the 0 position.

If I have the window open this happens much sooner. After this it is not possible to switch to fan off - cos the knob is already in the off position!
With the temp dial set at full blue it blows ambient air, just a single notch of blue brings warm air through the side vent and slightly warm through the centre.
Set to White and it is too hot to breathe in no time.

I would like to be able to stop this fan running unless I want it, but am at a bit of a loss as to how to do it - unless it is simply the dial/rheostat has gone funny.
With the EC enabled you get better temp control obviously, but still cannot switch the damn fan off!
Given the reaction to open window I'm thinking some sort of interior temp sensor issue, does this live in the interior light cluster - I think I recall seeing a post about a sensor fan in the boot???

Any thoughts or suggestions very welcome.

bin

 

[jberks]

it sounds like a switch fault to me.
The EC button doubles up as the REST button if memory serves. With the aircon off, the EC light should be on all the time when the engine is on. You say it isn't - this is clue 1.
That light also doubles for the residual heat switch which puts the fan on slowly without any reference to the fan switch - clue 2?.
The temp control isn't supposed to affect it but then again it's not supposed to work at all when the engine is off so with power running to and from places it shouldn't, all bets as to behaviour are off anyway.

So, if i had to guess, Id say there is an intermittent short circuit in the aircon/rest button and the rest circuit is getting power when it shouldn't. What that does in turn to the aircon on-off circuit I have no idea but clearly its behaviour won't be as expected.

I suspect you need a new heater control panel but don't take my word for it.

 

[The Rock]

If you have selected to have the Air Con off, ie EC light ON, turning the fan switch to position 0 or 0.5 will make the EC light go out. If your light is flickering my guess is that either the switch is faulty or the regulator is kaputt. I'd try a regulator from another vehicle first. I believe it's an easy thing to change. My guess is that the switch would be a little more difficult to change.

Rock.

 

[bin]

If you have selected to have the Air Con off, ie EC light ON, turning the fan switch to position 0 or 0.5 will make the EC light go out. If your light is flickering my guess is that either the switch is faulty or the regulator is kaputt. I'd try a regulator from another vehicle first. I believe it's an easy thing to change. My guess is that the switch would be a little more difficult to change.Rock.

Ah! that's interesting - the reverse is actually what happens during phase 1 - the fan is off, the light is off, but shouuld be on. When I turn the fan to 1-5 the red EC light comes on. Turn the fan off and it goes off till phase 2 when it's on all the time.

jberks - thanks for that - you're right, when it is on the fan - though the speed is at 0 - the speed is the same as you get from the Rest button.

Curious - when you lean on the the EC button for 10 seconds the Rest button light flashed twice. After doing that the fan stays OFF a lot longer.......

I have a feeling this is going to need a new switch panel not sure if it's a DIY job or not.

Thanks a lot guys anyway

Bin

 

[The Rock]

SNIP
- the fan is off, the light is off, but shouuld be on.
SNIP

Bin

Bin, I can't work out from your post if you've understood this bit or not, sorry. But just to be sure I'll say it again. "If the fan is in position 0 or 0.5 the EC light will be OFF, regardless of whether you've selected A/C off or not."

Rock

 

[jberks]

I have a feeling this is going to need a new switch panel not sure if it's a DIY job or not.

if it does - I believe its a straight forward job and I've seen new ones come up on ebay.

 

[bin]

Bin, I can't work out from your post if you've understood this bit or not, sorry. But just to be sure I'll say it again. "If the fan is in position 0 or 0.5 the EC light will be OFF, regardless of whether you've selected A/C off or not."Rock

Absolutely Rock, and that was the bit that drew the conclusion that the switch is faulty. To start with the light is off (I originally thought it would be on all the time the EC switch was set to off - your info has cleared that up thanks) - after a while it flickers to on and the fan comes on - even though the dial is at 0 and the aircon is off and the temp set at top blue on thumbwheels.

Regards

bin