760 2.3 ACC query

This question is aimed at the 760 2.3 4cyl cars (1990 vintage ) that have
ACC ( its the aircon that keeps at a steady temp once you have set it) and
turbo

If you have one of these does it do the following

In ANY configuration a/c on or off, heater vents in any position
do the vents shut ie no air comes through when the turbo needle gets to half
way

Once i lift off the accelearotor then everyting is back to normal, but as
soon as some oomph is needed.... no blow

The situation is similar to the old Ford vacuum wiper system.
I have looked at(but only looked!!) at the air reservoir on the passenger
side, but cannot see anything weird.
The two one way valves that are in the tubing leading from the inlet
manifold to the tubes that dissappear ino the bulkhead seem to operate on
lung suck pressure, but could it breakdown under the vacuum of the engine?
Any theories out there?
It has even got the VOC and a few franchised garages flummexed

Thanks
Ron

 

I'm not particularly familiar with the setup used in the 760, but there's
two things that should prevent this, one is a checkvalve, though I don't
know where it's located for sure but on a 240 it's right off the intake
manifold and the other is the electric vacuum pump which is under the hood
on the inner fender. If this pump is running then you may have a vacuum leak
somewhere preventing it from pulling a vacuum when there's no engine vacuum.

 

James

Thanks for the info.
I didnt know there was an electric vacuum pump!!!
another bit of the equation

Ron

 

No 1990 760s ever had ACC.

It's not normal. Read the BrickBoard's FAQ. This subject is covered in
graphic detail.

 

The gasoline 760 didn't have a vacuum pump after 1987, so don't look for
it on yours. The 2 check valves in the vacuum hoses just before they
narrow down to the small plastic hoses that go through the firewall.
The vacuum is leaking back into the engine when the intake manifold
pressure rises, that's what those valves prevent. The system is
designed to default to full heat and defrost when the system loses
vacuum for safety reasons - that's why you lose flow to the dash vents.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Ah, the 760 I've worked on just happened to be an '87, didn't realize the
newer ones didn't have the pump. I could swear I saw it in an '89 at a
junkyard once but perhaps not.

 

Surely the 760 Turbos had an electric vacuum pump until the last ones. They
had the B230FT engine. They may not have made them for the States but I was
sure that they did. I didn't think that the PRVs had one as they didn't come
equipped with a turbo (except aftermarket modded ones).

Cheers, Peter.

 

All 760 Turbos in the US from '85-on had the B230FT engine. Volvo never
produced cars with a turbocharged V6.

 

No, (over here anyway) only the ACC cars (-87) had the pump. ECC cars
didn't need as much vacuum supply, so the check valve and vacuum
reservoir was adequate. (except when the check valves fail)

As an aside for those that don't know, the ACC (automatic climate
control) system was a little bit on the Rube Goldberg side, with a
complicated electro-mechanical vacuum controller. ECC (electronic
climate control) was also automatic, but they had to change the name to
show it was different (and much better). ECC moved vacuum control to a
bank of solenoids controlled by electronics.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

If you read like an Englishman you would have had no need to reply to my
post.

Cheers, Peter.