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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

Reply to
Ron
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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.

Reply to
James Sweet

James

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

Ron

Reply to
Ron

No 1990 760s ever had ACC.

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

-- alex

Reply to
Alex Zepeda

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.

Reply to
Mike F

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.

Reply to
James Sweet

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.

Reply to
Peter K L Milnes

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

Reply to
James Sweet

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.

Reply to
Mike F

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

Cheers, Peter.

Reply to
Peter K L Milnes

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