A/C vents

ATOMICDR

MEMBER
1998 MERCEDES BENZ C230
2.3L
4 CYL
2WD
AUTOMATIC
150,000 MILES

Recently the A/C stopped blowing as strong through the two middle dash vents and started coming out of the defrost vents up on top of the dash. What do I do to fix it? It still works fine out of the vents on either end of the dash.

Monday, August 10th, 2020 AT 10:07 PM

6 Replies

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi,

The air flow directions is controlled with engine vacuum. You may have a small leak. Do me a favor. When driving, pay attention when climbing a steep hill if the problem gets worse.

I attached a pic below (it's confusing) and circled the vacuum actuator that may have a leak. These things are under the dash. See if when the car is at an idle if there is a hissing sound coming from around that area or anywhere under the dash.

Let me know.
Joe

Image (Click to make bigger)

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Monday, August 10th, 2020 AT 10:49 PM

ATOMICDR

MEMBER
41 POSTS

I will check that in the morning, however I cannot make heads or tails out of that diagram. I'm not sure which end is up/down left/right in that picture. I'll start it up and listen real carefully for the vacuum leak and hope it's not near impossible to reach.
I'll let you know what I find. Thanks for the heads-up.

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Monday, August 10th, 2020 AT 11:38 PM

ATOMICDR

MEMBER
41 POSTS

Well guys, I gave it shot. Listening for any possible vacuum leak sounds in, around, under the dash. Fan on low, mid, high. A/C on, off. Engine on, off. I couldn't get a read on anything sounds or otherwise. My hearing may be getting about as bad as my eyes now. Any other method I might use to locate the leak?

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Tuesday, August 11th, 2020 AT 7:26 PM

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

No problem. The leak could actually be under the hood and causing the pressure to lower to the HVAC. Here is a link that explains how to check for a leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know if you find anything.

Joe

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Tuesday, August 11th, 2020 AT 11:55 PM

ATOMICDR

MEMBER
41 POSTS

Hey guys,

Sorry I haven't been on this page for a couple of weeks. Been busy. Anyway, with regard to my car with the A/C issue. It's extremely hot here in the southwest and my A/C is at best providing me with 80%, what with the two middle vents being redirected to the defrost vents. Whew! I tried to find any vacuum leaks but I haven't been very successful, but I did find this; when I attempted to redirect the flow of air via the different settings on the dash by pushing the button. The little arrows would point to the different possible vents properly, but the air never redirected to anything except where it was already coming out. I suppose I'm lucky that it didn't decide to alternate to the heater vents and then get stuck there. I'd be even worse off. Is it possible my problem lies within that unit in the dash? Or?