Difference in Heater boxes 1980 to 1981

Dean_Fuller · 04-08-2011, 01:15 PM

Okay now I'm a little confused. ( imagine that) Jim was nice enough to sent me a heater box out of a 1981 US he had. I was just going to reuse the evaporator core and a few small parts off of it but now I am wondering if I just need to use the whole box. The reason I removed the box to begin with is there was a very focused condensation problem on the windshield after use coming from the defrost vents. So much so that water would DRIP off the inside. I BELIEVE the problem was a leaking seal at firewall/beater box. Heater core did not leak. Now here is my problem. I am seeing a difference in the boxes that just don't make sense to me.

Original 1980 box .
1) has NO riveted bracket on the left side for VAC unit that controls the defrost flaps.
2) part 25 has side linkage that connects flap doors top and bottom on the opposite side as shown in dia below.

New 1981 box.
1) part 41 and linkage in pic below was NEVER there. Holes are not present in box although they are located...not punched out. Part 41 controls the shut-off flap.

Does anyone know why there would be this much difference in a 1980 and 1981 box? I'm not sure which to continue with.

MPDano · MPDano's Garage

Can't you just Frankenstein one to the other?

Dean_Fuller · 04-08-2011, 02:09 PM

yes...but which? If its not right getting to it again will be a major pain. Why would one have a shut-off and the other not? Unless the two operate different which I would understand if I could find any info showing that.

Dean_Fuller · 04-08-2011, 02:10 PM

Leo..do you have a pic of the top of your heater box you could post??? Just remove the loose cover. That would help.

Dean_Fuller · 04-08-2011, 02:15 PM

I just looked on my 89 S4 and there is NO shut-off. So I assume it was eliminated at some point. Its VAC controlled so I'm thinking of taking it off the 81 box and capping the vacuum?

MPDano · MPDano's Garage

Sure, when I get home unless someone beats me to it. Oh, which car? 83? My 81 is still in the Painters Shop.

MPDano · MPDano's Garage

Quote:

Originally Posted by Dean_Fuller

Leo..do you have a pic of the top of your heater box you could post??? Just remove the loose cover. That would help.

This is on my 83. FYI, thanks for helping my fix my Fan Blower/Defroster unintentionally

Dean_Fuller · 04-08-2011, 05:50 PM

Thanks...looks like the shut-off flap was eliminated after 1980 model. That is interesting. I think I will leave it off Garrett's. I'll just have to do something about the vacuum.

Landseer · 04-08-2011, 10:04 PM

Dean,
Slight side topic. What do the three legs of tube #5 attach to?

Am hunting for why I get water leaking into the firewall near the gas pedal / tunnel when it rains.

Great pictures. I learn a lot from yours and MP Dano's posts. Thanks.

joejoe1 · 04-09-2011, 06:39 AM

Could the difference be '81 has auto hvac controlled by outside sensor and internal one on dash? I thought early cars were more manually operated (just guessing) Bottom of #5 (drain tube)runs outside underneath car and other 2 connect to bottom box?

Dean_Fuller · 02:55 PM

Quote:

Originally Posted by Landseer

Dean,
Slight side topic. What do the three legs of tube #5 attach to?

Am hunting for why I get water leaking into the firewall near the gas pedal / tunnel when it rains.

Great pictures. I learn a lot from yours and MP Dano's posts. Thanks.

Many thanks...I sometimes think I ask too many questions but I would just waste time if I tried to figure out what others have all ready done themselves. I swear if it weren't for this site and a couple others I don't think I could own this car.

Stick a water hose down inside the driver side of the heater box. That is what I did and it was easy to see where the leak is.

http://forums.rennlist.com/rennforums/928-forum/588476-major-condensation-inside-windshield.html

Notice starting with post #10.

Garrett's leaked right above the excelerator....sounds like yours is exactly the same. The heater box seat to firewall has failed. You will have to remove the box and reseal to fix it properly. I wish it was easier but I fear not. LOTS f work to remove. I did find the the correct sealant. 3M strip caulk. 60 feet for $24.00. Its non asphalt so it stays tacky and will not dry out. years ago I used it to seal windshields. Sealant out of a tube is too liquid for the job and will leak again. This is not a job you want to have to redo 4 years down the road. Take lots of pics as you disassemble....so putting it back will be easier.

The #5 hose is to drain the box if the evaporator ever froze and thawed. I will have to check where the other end connects.

Landseer · 04-09-2011, 09:38 AM

Thanks, please let me know.
But it sounds like you've nailed the source.
I forgot about the other thread (referenced)

So you know, I've got 2 84 cars and the 85 ALL leaking right about there.
Insulation under the pedals was soaked way up-under on two of the cars and had to be cut away.
Looks like you've identified another issue that emerges in the later years of the cars!!

Dean_Fuller · 04-09-2011, 05:24 PM

Actually I was amazed that at the time I was investigating it the only leak problem people were talking about was the blower above the fuse panel. But this EVAP box has the same leak issues and a lot harder to fix than the blower box. If you or I were closer I would help you on it....one at a time right!