Hi all - I've asked this question in my build thread, but I'm thinking I might get more eyeballs in a separate post...

I'm in the process of refurbishing my '83 Rx7 GSL. I'm tackling replacing the heater core at the moment. I've recently pulled the dash out of the car to get to the heater box:


I have a donor heater box (with a good core) so I know that there are two nuts attaching the top of the box to the body of the car. There is also a third nut which attaches to the firewall very close to where the heater lines pass through it. It appears this third attachment point is behind the air conditioner evaporator box (to the right of the heater box). I have tried, but there appears to be no way to actually reach this third nut without removing the evaporator box. Is this the case? Do I have to crack the A/C system in order to get to the nut and free the heater box?

My A/C (original R12 setup) actually seemed to be working - at least it was blowing cool air. I would hate to have to crack it open if I don't have to...
Any pointers greatly appreciated. (even if it's just confirmation that the e-coil has to come out)

As an aside... When the heater core went out on me (sometime in the early '90s) I recall trying to get to it at the time and eventually giving up. Since that time I've always had this vision of the Rx7 assembly line starting with an empty hook with the first person on the line hanging the heater box on the hook, then everything from that point forward just bolted to the box. Basically the whole car built around that stupid heater box. From what I'm finding now, I'm beginning to think I wasn't very far off...

 

If it were me, I'd evacuate it and switch to the latest and greatest refrigerant. If you do it now, it may save time down the road.

To your original problem, if I remember correctly, three seemed overkill. You might be able to slide a hacksaw blade behind there.

 

You may be able to loosen the evaporator case and carefully nudge it out of the way enough for fastener access. The hardlines are soft aluminum and are flexible to an extent.
If it has R12 and is working, I say leave it alone if at all possible.

 

Hey peejay, your suggestion *almost* worked...
With the e-coil box fasteners removed it would move a little and I was (just barely) able to get a socket on the offending nut. I got the nut off and then realized that the heater box still isn't going to come out because the two tubes that extend through the firewall need to come forward about 3 inches before they get all the way to this side of the firewall...
So close, but no cigar. I need another inch or two of clearance.
I think the only option at this point is to bite the bullet and crack open the A/C system so I can unhook and remove the e-coil. I so wanted to avoid that hassle, but the heater core needs to be replaced (and the vent flaps in the heater box need to be refurbished)... sigh...

Ckforker -- if I have to touch the AC system I'm seriously considering putting it back in service with R-152a (as described elsewhere in the forums)

 

Hey, you live in Marlyand -- what do the temps reach there -- 85?? Two days per year?? Cowboy up and go without AC

 

There's lots of humidity! I'd definitely want A/C. How much fun can you have cruising around if you're hot and sweaty?

 

Yeah, and while we may only get two days at 85, we get several dozen that are in the 90's...