1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Ed,
Sorry about that last post!
I'm pretty sure that you CAN have a good vacuum reading at idle, like your 18" Hg, and STILL have a vacuum leak.
My guess is that the idle problem lies in a vacuum leak in the HVAC system, since your idle gets steady AFTER you put on the a/c. I don't think it's an electrical issue related to the a/c, but rather a vacuum issue that is a/c related. Let me explain...
When you put on the a/c in SAABs (you know this already), you:
1) turn on the a/c compressor circuit (via electrical push button) and
2) turn on the fan/open air distribution vents via the big knob--usually to the small < > arrows, the dash vent position.
The knob for #2 is controlled by a combination vacuum AND electrical switch.
I bet your HVAC system's vacuum reservoir (white ribbed canister on pass. side fenderwell under the hood) is either leaking or a hose to it is age-cracked and split apart (happened on my Mom's '90 900 the other day).
Check the vacuum hose which runs from the engine's intake manifold nipple to the vacuum reservoir (it goes up underneath the rear edge of the hood, along the hood weatherstrip at the firewall and over to canister). This reservoir, as you may already know, provides a reserve of vacuum to operate the air distribution (vent) flapper door motors inside the cabin as well as vacuum to operate the fresh air/recirculate door over top of the air condition plumbing (evaporator, I think it's called).
Sometimes these reservoirs crack with age/heat. You also may have a vacuum hose slipped off under the dash (eeeek!) or a leaky vacuum motor in there, or at the recirc flapper door. One of my vent flapper doors (I wish I knew which one) leaks and causes the whole system to leak, making my 900 quickly use up the vacuum reserve from the canister. Result? On long uphills, the air gradually starts coming out the defrost vents and not out the dash vents (with knob set to < > position)!
So, first check all the vacuum hoses you can see under the hood, whether HVAC related or not (like AIC, etc). If THAT doesn't find you a leak to fix, then get a handheld vacuum pump w/guage and pull a vacuum on the vacuum hose going to the recirculation door's vac motor, for starters. No leak there? It may very well be a cabin air distribution door motor, requiring speaker grill and/or dash removal to track down the culprit.
I hope this helps!
Micah in NC
'84 900S, 237K mi.
posted by 216.77.233...
, Fri, 13 Jun 2003 10:46:47
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