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how quickly should air start blowing inside?

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signifer's picture
Ashburn, VA
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2006 E350

Hi,

Recently, our 2006 E350 sometimes takes 10-20 minutes before any air will start blowing in the car even though the temp gauge shows the engine is fully warmed up. Without air blowing the car gets humid and stuffy inside.

This seems most likely to happen when the outside temperature is around 60 degrees; if it's lots hotter or colder, the heat or a/c comes on fine. I don't remember it acting this way before.

I took it to the dealer and they looked at the codes, found nothing wrong, and said all was well.

Any ideas what might cause this?

Thanks.

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JBE63's picture
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Re: how quickly should air start blowing inside?

Not sure if I'm understanding correctly, but are you saying air won't blow when you turn up the fan or put it on max cool (or defrost)? Is it because you have it on "auto" mode and the selected temperature is close to the same as the ambient temp? (e.g., your 60 degree versus really hot or cold outside phenomenon.)

If you do have it on auto, try selecting a radically different temp setting. The fan should blow immediately. Or, turn auto off and manually select the fan's settings.

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signifer's picture
Ashburn, VA
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1990 300E
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Re: how quickly should air start blowing inside?

Hi,

Let me try to be clearer.

The problem is that sometimes when I first start the car nearly no air comes from the vents with the system set for 68 or 70 degrees in Auto and the outside temp around 60. If I play with the fan speed buttons, it makes a slight difference but there is still little air coming out even with the fan set on high. On an older car I would have said the vacuum system wasn't opening the vents right or the evaporator had frozen.

I haven't tried playing with the temp setting but if it is hot or cold out the air is quite enthusiastic until the temp inside is about right and then it blows a gentle breeze which is much more than when the car is started with the outside temp around 60 and the inside temp set to about 70.

I have had the same symptoms before and the dealer has replaced the blower control and motor (twice). I'm not sure that's what the problem is but it seems to fix it for about 6 months; it has come back. When I took it to the dealer this time he said he found nothing wrong. I'm guessing there is some failure mode where the control system doesn't control the air flow right but I don't have a clue how this system works.

Thanks for any help.

Best regards,
Richard

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Bela's picture
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Re: how quickly should air start blowing inside?

I would assume that the ventilation system reads the temperature of the air in the vehicle and the air temperature it can deliver, and until it can deliver warm enough air to provide the temp you ask for, it does not blow. In other words, it doesn't deliver cool air when you call for warm. So however long it takes to warm the coolant, it restrains the air flow to warm the passenger compartment. The replacement by the dealer of the controls and blower would be quite a drastic response, unless the controls include a thermostatic sensor that guides the system. However, it does sound like 20 minutes would be excessive for achieving the required temperature for delivery– I would expect more like 5 minutes.

Bela

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Re: how quickly should air start blowing inside?

On my 2004 on a colder day it only takes a few minutes before the car starts putting out warmer air. Sometimes I cannot feel it on my feet but the circular lights showing fan speed show me that the fan is indeed blowing out air.
Michael in Arizona.

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Michael in Arizona (Desert Stars) 1988 560SL in Signal Red, 70,000 miles 2004 E320 4Matic wagon in white, 72,000 miles 2008 S550 in Black, 28,000 miles

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signifer's picture
Ashburn, VA
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Re: how quickly should air start blowing inside?

Thanks for the replies.

It doesn't seem to be linked to coolant temp. When it is cold, it takes the car just a couple of minutes before the blower starts and as the car gets warmer the blower speed picks up; this works fine.

The problem here is that when the temp outside is about 60, it can take 10-15 minutes before the blower starts to move any air; this is well after the temp gauge shows the car is warm and much longer than it takes when the temp outside is cold. When this happens, the car tends to get very humid (from people breathing) and really stuffy because no air is moving.

Today it was 70 outside with the temp set at 70; the blower started to move air immediately at a very low speed.

It's really strange that the blower doesn't seem to like an outside temp of 60. I'm perplexed...

Best regards,
Richard

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David Brittain's picture
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Peter:The situation you've

Peter:

The situation you've got doesn't sound normal to me. I've never had an E-Class but I would think the heating/cooling system would be about the same.

I keep my C-Class on automatic all the time and set at 72. In summer, the AC starts immediately to cool the car down. In the winter, it appears the system will not blow cold air on you. It will start blowing when the engine temp is high enough to give you warm air. However, this happens in a matter of a few minutes, probably under five.

If your system is taking 15-20 minutes to begin giving you heat, something has to be wrong.

Dave

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David Brittain Folsom CA Sacramento Section

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