[W126 Coupe] AC Problem Part 3

[Dick Spellman]

Hi Tom:

So you were able to get good AC performance on a 70 degree day and at all speeds and the blower and upper vents are confirmed as working properly.  Have you confirmed that the air make-up door (fresh air/recirc door) just above the blower motor and behind the passenger dash glove box is working properly?  That is with AC on the door is open only 20% or with the AC set to MAX the door is filly closed.  Closed being up against the engine firewall not down against the cabin wall.  Pull the glove box and observe it's operation to confirm it's working.  If you have access to a MightyVac (MV), pull the vac lead along side the ACC controls (look for the nicely colored vacuum distribution manifold) attach the MV and pump it up to see if it holds a vacuum.

The only other possibility would be the performance of the refrigerant when the outside air is hot and the 'engine coolant' is running hotter than it was today your 70 degree day.  Which begs the question was the coolant temp in the same range as you reported when it was 95 degrees?  I am going to bet it was fine which means all of your work was fine up till this failure.

When you go to adjust the belt tension on the Nippo compressor what are you adjusting?  Just pulling up on the idler pulley, right?  And then you snug the pulley hold down bolt which is a 17 or 19mm and when you check this later it's still torqued and the belt seems properly tensioned when first done?  Just how slack does it get?  Do you hear the belt squealing when the ac clutch engages?  Does the squeal go away?  No squeal at all and the belt is therefore suffiently tensioned to do the job.

Tom, I think the first step is to check and see if the vacuum elements (there are two) on the fresh air/recirc door have failed to cause your most recent problems.  If one is gone, replace both element rubber diaphrams.  George Murphy sells the kits, they work just fine.  If you find this to be the problem, call me and I'll provide the email and phone info.  Not handy just now.

Dick
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