I am in the middle of replacing the evaporator on my 740 turbo. As described in the FAQ, putting the lower cover back on the HVAC box is extremely difficult. What the FAQ doesn't talk about is the possiblity of looseing that side of the whole box from the firewall. If I could do this -- I think even 1/2" of wiggle room would make this job MUCH easier.

So - does anyone know how this beast attaches to the firewall? I found one bolt near the evaporator drain, but it didn't seem to help much. Another bracket inside at the top of the box didn't help much either. Right now, it looks like the fresh air intake is holding it fast in place. But before I remove the cowling to look for a bolt under there -- Anyone know right away whether there is a bolt or bracket under the cowling that will free this side (the fan side) of the HVAC system?

Thanks -

AJ

Got it installed! Thanks for all the help. I think the problem was I loosened too many bolts in the beginning. I removed the nut that goes on the stud at the firewall (engine compartment, near the receiver/drier), and I removed the hex bolt that holds the air box (inside, next to the evaporator). What that did was allow the whole thing to drop a little. It was slight, but it was enough to prevent the bottom cover from seating all the way back (it ran into the firewall instead).

So - I think because I loosened these parts, I had to free up the whole HVAC box in order to move it enough to get that bottom cover back on.

Anyway, now that the cowling is off, I can also work on the wiper mechanism, which needs some attention. :)

Looks to me from the diagram in the manual that there are several bolts holding this top half of the plenum unit to the firewall:
-one stud on the left side with the nut inside the engine compartment
-one bolt just above and to the left of the evaporator
-a strap of some kind above the fresh air intake.

You can remove the cowl and the fresh air intake very easily (see the FAQ in the windshield wiper section).

Where was the bottom plenum half difficult to remove when you pulled it down at first? What hung up when you tried to replace it?

I have the Volvo Manual for AC. Which beast are you talking about?
>>does anyone know how this beast attaches to the firewall

If you're talking about the evaporator itself, it fits snugly in the upper housing. The manual mentions applying a thick piece of butyl tape to the rear edge at the top of the evap. Evap will then remain in place more easily in housing during installation. The mechanical connections are the other side of the firewall in the engine compartments to the drier and condenser lines.

What cowl are you thinking of removing? Removing the dash won't help you.

I had problems with the rubber seal on the evaporator binding up and causing interference. Make sure its clear of the housing.

Let me know what year 740 you have and I'll look up the specific procedure and diagram. Also, contact me via email and maybe I could fax a diagram if that would help.

Tom

The "beast" is the whole plastic housing. I removed the bottom cover (fan and all) to r&r the evaporator, but now I can't get the bottom cover back on. When I pull on the top of the housing to get some slack, it doesn't budge. I thought if I could loosen the top housing from the firewall enough to move it around a little, I could put the bottom cover on much easier. My guess is Volvo had this HVAC unit assembled out of the car and installed the whole thing as a unit -- not necessarily meant to be serviced on the car.

The car is an '88 740 GLE turbo wagon w/ manual AC controls. If you have the procedure outlined in your manual or a diagram, that would certainly help. :)

Thanks --

Adam

Mine is an 85 turbo so I don't know if it is much different, but I can tell you it is a pain to do what you want to do. I had to replace my upper and lower plastic evap housing (long story).

Anyhow, on mine there is one nut attached on the engine side of the firewall to a long bolt in the area just above the evaporator drain hole.

There are two more on the other side of the engine where the hoses attach to the heater core.

Third, there is a big screw with hex head as I recall attaching just above the glove box. If you look for the heater control cable, you are in the right general area of that screw.

Last, but not least, are two screws (10mm hex heads) that attach to the fresh air intake from above. To me, those are very hard to get at. You can take the panel off which is the fresh air grill (under the windshield wipers) or you can reach up from below with a wrench, but it is hard to do. I broke mine and it cost hundreds to replace that housing so be careful. You can feel the screws by reaching up the air intake (above the blower) until you feel a metal support bar. The two screws go into the ends of the metal bar from above. In order to remove them from the inside, you can use a socket wrench that makes a 180 degree turn.

I don't know how much you can move the air box without removing all the other duct work, but those are the main attachment points.

I did not try to do that, and it is hard to plug the housing back in. One thing that helps is to reach back with one hand and press the evaporator away from the firwall a bit. The housing catches on the tube on the bottom of the evaporator. I also cut the drain foam plug in two on the bottom and resealed it with RTV. (that gives you a little more room).

One tip, I found that doing this job is much easier if you remove the front passenger seat, then lay some padding down on the floor. I just put my evap back in on Sunday, now if I can figure out how to get the condenser replaced my A/C will work soon.

Good luck,

Randy

Randy, can you take a look at the "evaporator replacement" section of the FAQ and let me know how to improve this? Just email any tips you have.