67 Eldorado ACC/Climate Control (Trouble Shooting Question)

[Antoni Deighton]

I've been trying to troubleshoot the climate control on my '67 Eldorado. I had the freon system fully charged. The car had the usual blower motor works in FOG and ICE modes, but would not come on in AUTO modes. I took the power servo apart and cleaned and polished the rotary valve before reinstalling. After that the blower motor no longer came on in FOG/ICE modes (although that makes no sense to me since those modes apparently bypass the power servo completely. When I push on the underside of the master vacuum switch (as per Lynn Nicholls' tech article http://www.stampie.com/tech/Climate1.html) the blower motor comes on at varying speeds in all modes, so I know the blower motor works, the power servo works, and the blower relay works. Lynn Nicholls also describes how to check the AC/Heater vacuum motor, but as far as I can tell that seems to be working.

So here's my question: Any thoughts why the master vacuum switch may have been working before I took the power servo out and is no longer working?

[Dave Shepherd]

How about the rotary vacuum valve in the power servo?

[Carl Glass]

I have the same demon that prevents the blower from running except in Defog and Deice.  But I havent invested ANY time in diagnosing my car.  Just reading all that I can on here.

Carl

[Antoni Deighton]

@Dave -- yes I've pulled thenpower servo and removed any warpage from the rotary valve. In fact I went ahead and rebuilt the entire power servo to make sure everything functioned properly: a good thing too, since I found the second time I had reinstalled the lower half of the rotary valve incorrectly!

@Carl -- it sounds like you have a problem with the power servo. On the defog and ice settings the power servo is bypassed and the blower comes on right away. There's a good post on Gerald Loidl's site http://www.eldorado-seville.com about how to fix it.

The problem I'm having is that the power servo works properly turning on the blower on low/high in auto, etc but only but only if I activate the master vacuum switch manually. The funny thing is that it seemed to be working fine in FOG and ICE modes before I rebuilt the power servo, but now it wont turn itself on in any of the modes!

I fear that it's something I've done but I'm not quite sure how they are related.

["Cadillac Kid" Greg Surfas 15364]

Antonie,
You might want to check ALL you vacuum lines for bad connectiions or hose leaks.
Greg Surfas

[Glen]

Greg is right; the master switch is pulled in with vacuum.  If the vacuum in the system is low then the master switch won’t work. 

Another thought; how did you polish the rotary valve?  If you used a compound of some kind you may have plugged one of the passages. 

[Antoni Deighton]

@Glen - Good thought. I didn't use a polishing compound, but I did wet sand it with 600 grit, then 1500 grit sandpaper, and I lubricated it thoroughly with WD-40. I pulled the power servo again, and took another look at the rotary valve. I think the WD-40 might have been plugging the lines.

This afternoon I continued polishing with 1500 grit, and cleaned it (compressed air, and a light film of WD-40 this time). Now the blower works fine and comes on in vent, fog and ice modes. And it will come on for about 20-30 seconds in Auto mode.

It's much better than it was last week, but I'm wondering if perhaps I should polish it some more with compound this time for a glassy finish. (The 1500 grit leaves a lightly brushed finish.)

Anyway, it's nice to know that the main parts of the system seem to be working and that it's getting narrowed down to a specific solution!

Thanks for all of your inputs...keep the thoughts coming!

A.

[cadillactim]

Antoni

WD-40 won't last, as vacuum will draw it out of the valve.  Once you refinish the surfaces you must use a proper lubricant for the repair to last long term.  Otherwise, the metal-to-metal surfaces will scratch and gouge one another, and you will end up with a vacuum leak again.  Also, what did you sand the valve halves on?  Are you sure you removed all warpage and pitting from each half?  Earlier you had emailed about my troubleshooting manual, but I never heard back.  Properly reconditioning these valves is covered in the manaul.  Tim

[Antoni Deighton]

Tim,

Thanks for the recommendation about WD-40. I got your email...I'll be contacting you about it a bit later (just figuring out about the faceplate!)

I'm not 100% sure I removed all of the warpage, but there was no pitting. I guess I lucked out!

Thanks,

Antoni

[Glen]

We are assuming that when you resurfaced the valve halves you used a very flat surface like plate glass as a backing for the sandpaper.  If not you may have a curvature to the valve faces and they will not mate up right and cause a vacuum leak.