Has anyone ever encountered a situation where the A/C
suddenly works only from the Left vents and hot air
blows from the Right vents. Is there a separate swtich
or flap that controls each side. This is realy peculiar.
Thanks for any replies.

--
-Cool Volvo- 1982 240 4 Spd OD w/ 231K, 1989 240 5 Spd w/ 220K. Used to own 1966 122, 1968 144, 1970 145, 1972 144, 1980 245

Another approach -

Cold air destined for the right side outlets doesn't get there.

Set up for a/c cold, floor vents opened, center and outside dash vents closed.
That way all the air should blow out the front and rear floor vents.

Feel around to see what temp air comes out which vent.

Reason: The outlets from a turbine (right = mirror of left) are only two. One supplies ALL the dash vents, center, defroster, feet, outside. The rear floor vent air comes from a totally separate turbine outlet.

So, if that rear floor vent has cold air, the problem is in the ductwork. A much cheaper fix, but a PITA, BTDT.

Hopefully that's the case, although danged if I can figure how that could happen. Check on all the vacuum motors and hoses.

Tip: If two ducts that are supposed to fit together won't, 1) try a lot, 2) DO NOT use duct tape. 3) Use a power screwdriver phillips 1/2 inch sheet metal screw (similar to the ones holding in the glove box) and only one will be needed.

Good Luck,

Bob

:>)

I've recently had the whole underdash heater/AC assembly apart, including all the ducts, for a blower motor and heater core replacement.

ALL air passes through the AC evap. then through the heater core. This is why you need a heater valve that shuts fully OFF to get decent AC. Air is all commingled downstream of the heater core in a plenum then it divides and is picked up by the left and right blower impellers and sent to the left or right duct systems.

I would bet on a failed vacuum dashpot or the vacuum line feeding it, so that you are actually getting no airflow out of that side - which in warm weather will feel like hot air compared to the side that's blowing cool.

My 940 has the famed 700/900 "vent weirdness" in which the dash vents shut down during acceleration. It feels like the AC has failed - until you reach down and feel the cold air now being blown at your feet.
--
Bob (son's 81-244GL B21F/M46, dtr's 83-244DL B23F/M46, 94-944 B230FD; grocery-getter Dodge minivan, hobbycar 77 MGB, and a few old motorcycles)

Bob,

I do understand the process of how the air passes through the A/C Evap
and then the heater core down to the vents. I'm sure that the heater
valve is shut off properly otherwise -> no cold air. Again, the really
peculiar thing is that all four vents are getting airflow, but only the left two are cold. There must be a flap, possibly vacuum-activated that either
allows some heated air in, or shuts off the cool air from the Evap.
Are there any good FAQ's on the A/C systems on this forum?
--
-Cool Volvo- 1982 240 4 Spd OD w/ 227K, 1989 240 5 Spd w/ 214K. Used to own 1966 122, 1968 144, 1970 145, 1972 144, 1980 245

Let's see.....if ALL the air that comes out the vents comes through BOTH the a/c evaporater and the heater core, and you are getting equal air volume from right and left vents, there must be something to make the difference.

First, if the air on the right seems heated, not just ambient temp warm, the heater is not fully shut off. There is an easy fix for that.

The air in the plenum is not separated by side, but it seems to me that the draw of air from the turbines would somehow make the air behave as if it was divided by sides. If that's true, then maybe somehow the evaporater is becoming frozen, but just mostly one side.

I don't know enough about a/c systems to know just what does happen when an evaporater freezes, or why (mebbe low freon?), but maybe another brickster with more knowledge will chime in.

Good Luck,

Bob

:>)

The flow on the right two vents is definitely just ambient temp.
But, could it be that Cool + Hot = Ambient.
Is there a possibility that the Heat Temp Control is only
partially working on the left side?
--
-Cool Volvo- 1982 240 4 Spd OD w/ 231K, 1989 240 5 Spd w/ 220K. Used to own 1966 122, 1968 144, 1970 145, 1972 144, 1980 245

Hey, I'm with the Bobs. Here's a photo that might explain a heater's preference for the right side. Feel that inlet hose and make sure it isn't warm. You're right. Warm + cold = something in between.

I'm vaguely familiar with seeing an evaporator icing up from one side, but not one on my car. I looked at an evap I pulled from a '90 to see if it is piped in such a fashion to ice up on the right side first, but it looks to me like the tubes are woven such to even it up all across.

So, here's what I would do if my passenger complained: Check the heater hose for warmth - that is so quickly over with and behind you. Then, with the phenomenon in progress, use a mirror through the recirc flap to view the evap fins for icing. That will be warm work, because it is best done from the passenger's (warm) side of your car.

bob is right your heater is on

It still makes no sense why one side would be cool and the
other warm. The heat temp control should either pump heat
or not pump heat.

I remember once leaving the heat on by mistake while turning the A/C on,
and it was not cooling on any of the vents.
--
-Cool Volvo- 1982 240 4 Spd OD w/ 227K, 1989 240 5 Spd w/ 214K. Used to own 1966 122, 1968 144, 1970 145, 1972 144, 1980 245

When my '90 is low on freon, it does that, charge it up...cold both sides.I still havn't figured that one out yet, possibly one side of the evaporator doesn't get cold?????
--
-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '82 Mercedes 300SD for sale

That's absolutely unbelievable!
When my other car was low on Freon, it would
only work intermittenly, but both sides worked.
I did notice bubbles in the dryer window,
which usually means the Freon is OK.
--
-Cool Volvo- 1982 240 4 Spd OD w/ 231K, 1989 240 5 Spd w/ 220K. Used to own 1966 122, 1968 144, 1970 145, 1972 144, 1980 245