Hi all, thought I'd share my recent foray into ACC repair:

Yesterday I replaced all the vacuum actuators (pods) for the climate control system in my sister's 1987 300D. Of the 6 total, only two are accessible without removing the dash - the pod for the floor vent flaps (pull the pushbutton unit to access this one), and the one for the defroster flaps (behind the glove box.) The other four - 1 center vent, 1 diverter, and 2 recirc - require pulling the dash. That means yanking the instrument cluster, steering wheel, p/b unit, glovebox, both lower trim panels, and then the whole dashboard. And then you need to pull off the top of the heater box to do the center vent & diverter pod, which is also a pain. This car (with 155kmi) had 4 bad pods: center vent, diverter, recirc (small lift), and defrost (small lift). Needless to say the system was NOT functioning as intended, although the ONLY symptom was a lack of air from the center vents with the A/C on. W124's are sneaky that way.

So, I've said it before and I'll say it again: If you own a W124, particularly one that's older or with high miles, you should check the operation of the pods to make sure your ACC is working as designed! It's easy to test. Pull the glovebox and the 7-port manifold is right there on the left side, attached to the heater box. Remove one hose at a time and connect a MityVac. Each hose should hold vacuum. If not, the rubber diaphragm for that pod is torn. You can identify the function from the ACC service manual, if you want to know what's not working (assuming it's not obvious). The pods from Rusty (or FastLane, etc) are ~$15-20 each for the single chamber ones (center vent, floor, and diverter), and $25-30 each for the dual chamber (both recirc and defrost). I've heard that George Murphy sells a diaphragm kit to repair the pods but I don't know details or pricing, or how hard it is to repair them.

It took me 2 hours to remove the dash, 1.5 hours to replace the 5 upper pods (I left the footwell pod alone), and 2 hours to reinstall the dash. Total was 5.5 hours. If you do this, I HIGHLY recommend replacing ALL the pods that require dash removal!!! This is NOT a job you want to repeat a few months down the road when the next old one fails. Change 'em all and then you don't need to worry about it for the next 10 years or 200kmi. The two exceptions are the ones that don't require dash removal; the defrost & footwell pods. These can be done at any time in 30-60 minutes.

Tips for installing: Leave the flat metal bars attached for the recirc pods. Undo the connector tabs at the pod and reconnect to the new pod. Most of the pods have a lock tab that must be pressed before they will rotate out (I learned that the hard way last time - don't ask.) The diverter pod is held in by 3 round metal press clips, so you need to break out the old one and save the mounting clips for the new pod. The center vent pod is the trickiest. Although the manuals says you need to pull the heater core (YUCK!) it is not necessary. Remove the white pin in the top door. Remove the door by flexing it out of it's hinges. Remove the flat metal rod from the pod. Pull the hose and twist the pod out, it will *just* wiggle out from under the mounting bracket. Oh yeah - just before you reinstall the dash, do the MityVac test one last time on all 7 hoses! Otherwise, if you forgot to connect a hose you need to repeat the 4 hour dash R&R job! (Oh, joy!)


For the record, of the three 1987 300D's I've tested, this is what I found:
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Car 1 (155kmi) - bad center vent, diverter, recirc, and defrost
Car 2 (229kmi) - bad center vent, recirc, and footwell
Car 3 (238kmi) - bad diverter, recirc, and defrost


And a couple more 124's I've tested since the original post:
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Car 4 (86 300E, 200kmi) - bad center vent, diverter, recirc, and footwell
Car 5 (87 300E, 110kmi) - bad center vent, recirc, and defrost



Part number list:
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124-800-00-75 = Defroster pod (dual chamber)
124-800-02-75 = Center vent pod (single chamber, twist-on)
124-800-03-75 = Diverter pod (single chamber, small, attaches w/3 clips)
124-800-04-75 = Recirculation / fresh air pod 1 (dual chamber)
124-800-11-75 = Recirculation / fresh air pod 2 (dual chamber)

124-800-01-75 = Footwell pod (round, small, to VIN A289309, 1986 to early 1987, two required)
124-800-09-75 = Footwell pod (rectangle, from VIN A289310, late 87 through 95, one required)


NOTE: Of the pods above, only the -02-75 (center vent) can be properly "rebuilt" using the diaphragm kits from Performance Analysis. The dual-chamber pods can only have the 'small lift' portion rebuilt properly. The diaphragm kits for the dual-chamber 'large lift' will restrict movement and should NOT be used... replace the recirc+defrost pods with new pods only! There are no rebuild diaphragms available of any kind (good OR bad) for the small round pods (diverter and early footwell), nor for the rectangle pods (late footwell).

Photos are at this URL:
http://www.w124performance.com/images/W124_dash/


Do yourself a favor - grab your MityVac, pull the glovebox, and check them out! Summer's coming up fast and a fully working ACC is a beautiful thing.





Best regards,

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