85 300D AC center vents

[funola]

I have completely rebuilt the AC in my 85 300D 3 years ago with a reman heavy R4 and charged it with R12. It's been working great. However, I noticed recently the 2 center vents are not blowing as hard as the 2 side vents. I am getting cold air at the foot well that is blowing harder than the center vents. Should I be getting cold air at the foot well or did some ducting come off?

I have read that weak center vents is due to a leaky vacuum pod that is not controlling the flap properly. Does mine sound like a bad vacuum pod?

[BWhitmore]

Are you asking about the temperature of the air or the volume of air coming from the center vents? If you have no air coming from the center vents you probably have a faulty center vent vacuum pod.

[h3ffe]

Yep. Unfortunately it is a dash out job to replace that pod. 10+ hour job.

There is another work around, however.

You can cap off the vacuum to the climate control and move the flaps that direct airflow to defrost, dash, and floor vents to a desired "set it and forget it" position.

For milder climates, a good mix might be 15% open defrost vents, 75% open dash vents, and 10% open footwell vents. You control airflow by opening and closing all the dash vents manually.

I have my W123 sedan set up this way and it works great. Saved removing the dash, but if I were ever in there for another reason (heater core, evaporator, or replacement if my dash cracks) then I would redo all the pods and replumb the system as from factory.

[h3ffe]

You are getting more air to the footwell because:

1. The center vent pod is failing, allowing the center vent flap to sag. As the tear in the vent pod diaphragm worsens, so will the airflow through the center vents. This pod is located inside of the airbox in the middle of the dashboard.

2. It is next in line in the path of least resistance for the airflow, now that the center vents are not opening as much as they used to. Airflow to the defrost and footwell will increase.



Additionally, you may have more vac pods that are bad, and you are simply unaware of it because they are marginal or the system hasn't exhibited symptoms yet.

[BWhitmore]

If you decide to remove the dash send me your email address and I will be happy to send you a set of written instructions for removing and installing a W123 dash. The job is not complicated at all and can be done with simple hand tools.

[funola]

Originally Posted by dogguy

Based on my experience with the 617.952 - 123.153:
> The side vents always seemed to blow a bit stronger than the center vents.
> "Should I be getting cold air at the foot well or did some ducting come off?"
The only way I know to be certain is to reference the applicable factory service manual diagram(s) and follow the vacuum element lines to their designated functionality based on which button(s) are pushed on the climate control unit. On the other hand, there is this: Are you experiencing any symptoms of vacuum leakage with the rest of the vehicle's functionality?

Not having any vacuum issues I am aware of. Central locking works fine for a few days w/o starting engine. Car shuts down fine. What color are the lines for the vac pods? I can check with a Mity-vac for leaks.

[funola]

Originally Posted by h3ffe

You are getting more air to the footwell because:

1. The center vent pod is failing, allowing the center vent flap to sag. As the tear in the vent pod diaphragm worsens, so will the airflow through the center vents. This pod is located inside of the airbox in the middle of the dashboard.

2. It is next in line in the path of least resistance for the airflow, now that the center vents are not opening as much as they used to. Airflow to the defrost and footwell will increase.



Additionally, you may have more vac pods that are bad, and you are simply unaware of it because they are marginal or the system hasn't exhibited symptoms yet.

Can you post a link to pics of the center vent pod?

[funola]

Originally Posted by h3ffe

You are getting more air to the footwell because:

1. The center vent pod is failing, allowing the center vent flap to sag. As the tear in the vent pod diaphragm worsens, so will the airflow through the center vents. This pod is located inside of the airbox in the middle of the dashboard.

2. It is next in line in the path of least resistance for the airflow, now that the center vents are not opening as much as they used to. Airflow to the defrost and footwell will increase.



Additionally, you may have more vac pods that are bad, and you are simply unaware of it because they are marginal or the system hasn't exhibited symptoms yet.

First photo in this post https://www.benzworld.org/forums/w123-e-ce-d-cd-td/1529793-center-vent-zip-tie-question.html shows a pink/ black vent pod. Is this the center vent pod you're talking about? You said it is "inside of the airbox" but it does not appear to be inside of anything.

Per that post, that vent pod can be accessed by removing the glove box liner.

[BWhitmore]

It takes about 1 hour to remove the dash, about 1/2 hour to replace the center vent pod and about 3-4 hours to replace the dash. I found it easier to replace the center pod (and actually all the vacuum pods) by using the appropriate size die to put threads on the legs of the pod and attach the pod to the holding bracket using nuts. Be sure to install the rubber “O” rings on each leg. The clips that come with the new vacuum pods can be really tough to install and quite often break the plastic leg off when trying to removing the clip; OR you can hold the center vent in the wide open position and using the appropriate sized wooden dowel or bolt to hold the vent open and forget about replacing the vacuum pod. Your center vents will be open all the time. You can adjust the air flow by turning the air vent open or closed.

[BWhitmore]

The center vent vacuum pod is pink & black and is attached to the front of the center flap using a metal bracket.

[funola]

Originally Posted by BWhitmore

It takes about 1 hour to remove the dash, about 1/2 hour to replace the center vent pod and about 3-4 hours to replace the dash. I found it easier to replace the center pod (and actually all the vacuum pods) by using the appropriate size die to put threads on the legs of the pod and attach the pod to the holding bracket using nuts. Be sure to install the rubber “O” rings on each leg. The clips that come with the new vacuum pods can be really tough to install and quite often break the plastic leg off when trying to removing the clip; OR you can hold the center vent in the wide open position and using the appropriate sized wooden dowel or bolt to hold the vent open and forget about replacing the vacuum pod. Your center vents will be open all the time. You can adjust the air flow by turning the air vent open or closed.

I am not looking for a lot of work so taking the dash out is out of the question for now. Can you take a look at this link https://www.benzworld.org/forums/w123-e-ce-d-cd-td/1529793-center-vent-zip-tie-question.html that describes accessing the vent pod by removing the glove box liner?

[BWhitmore]

I have actually replaced the pod by taking out the glove box liner. Believe me from my own experience, you wish you had removed the dash. Removing and installing the dash is not that difficult.

[funola]

Originally Posted by BWhitmore

I have actually replaced the pod by taking out the glove box liner. Believe me from my own experience, you wish you had removed the dash. Removing and installing the dash is not that difficult.

Don't want to replace the pod, only jury rig the flap.

[BWhitmore]

It is possible to rig open the center flap through the glove box opening. Study the picture you have and I would remove the panel below the dash on the passenger side in order to shine some good light under the dash. Good luck.

[funola]

This post has great pics Center AC vent not opening