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#705075 - 07/19/09 11:58 PM Replacing AC Evaporator and Heater core  
Joined: Feb 2000
Posts: 3,934
Dalt10 Offline
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Dalt10  Offline
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Posts: 3,934
Orlando,FL


This job is not as hard as it looks. I think most people can change the evaporater and heater core. It's mostly unbolt the top of the AC box, pull the cores out and put new ones in. My AC has been disconnected (no freon). So if you are changing your AC core and you still have freon in the system then you need to go and have the freon taken out. It would be a little easier if you have the hood off but sometimes they are a pain to get lined up right after taking it off. I used a 7mm, 10mm and 1/4" sockets for just about everything. There might be different sizes but that is what is on mine.


First thing to do is turn the key on just to move your wipers. I moved them up and out of the way. Unbolt the black trim piece at the bottom of you windsheild. And unbolt the windshield washers. Slide the black trim up just enough to get it out of the way.
Next thing is to unplug the 4 electrical connections on the AC box. Unbolt the plastic screen and pull it off the top of the AC box. Next is just unbolt all of the bolts you see on top of the ac box and the bolts that go into the firewall.

There are 2 bolts inside the box where the air comes in. Look down in the box where you took the screen out and you will see them. After all the bolts were out a used a razor knife to cut along the top of the box. Mine was sealed to the firewall. Before you can get the top of the AC box off you need to take the 2 brackets off on the firewall that hold the black trim. I think those bolts were 11 mm.

I took a scewdriver and pryed the box open easy so I didn't break anything. After it's loose just wiggle it around until it comes off. Here is the top of the box off the car.

The AC core just lifts up and out. Since I had the AC box top off I figured I might as well put a new heater core in. Unbolt the ground on the heater core and take the 2 hoses off. Then the heater core just lifts right out. You could spill a little antifreeze or water, so be carewful. There was a bracket on top of mine where the ground went and it held the core in place. It slips on the core itself. Look how it goes on so you can put it back on the new one. I should have got a pic of the bracket but didn't think about it. Make sure you take the foam piece of the old core and put in on the new one ( it goes around the metal pipes where they come out of the box). Before you put the cores back in clean out the box. Vacuum or clean it out by hand. Make sure the hole in the bottom of box is clear so the water (condensation) has a place to go.

Just set the new heater core in, bolt the ground and bracket together and hook the 2 hoses back on. The new AC core should come with sealing strips. If they did put them on (look at your old core). Then set it down in the AC box. Make sure you put the foam around the pipes the same way they came out.

I put some sealer around the top edge of the box before I put the cover back on. Set the cover down in place and start bolting it back together. I had a little bit of the sealer ooze out after I tightened down the cover. I just got a rag and wiped it clean. The rest of the way is just putting everything else back together (plug in wiring harness, washer squirters, black windshield trim etc).

I have to wait until I get the rest of my parts to get the AC going (compressor, drier, condensor etc). I figured this was the hard part. Make sure you start your car, warm it up to tempature and check the heater. If you lost some antifreeze fill it back up. If you are getting the AC going bolt everything else back together (lines, drier etc) and get the freon put back in. There are filters going in the line to the AC core. So if you are getting the freon put back in you need to change it.

Am sure some people can add to this and I might remeber something else. If there are any suggestions please do so.


"Make the rules up as you go"
US Army 1977- 1981
101st Airborne 31st Field Artillary FT Campbell, KY
1/1 Cav 280th ORD Schwabach, Germany
#836002 - 11/10/10 09:09 PM Re: Replacing AC Evaporator and Heater core [Re: Dalt10]  
Joined: Jan 2002
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1984_Z65 Offline
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1984_Z65  Offline
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Joined: Jan 2002
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Wahiawa, Hawai'i
Something to add:

When removing the top plate, there are little metal clips that hold the rubber gasket to the perimeter bolt holes. (The ones at the top that bolt it to the firewall.)

to keep from tearing the gasket, you can push the clip out through the bolt hole by pushing it towards the firewall as you pull the top cover away.


'84 SS 103K, '85 SS (Frame off)
'15 Silverado HD (Daily Driver)
'96 BBB Impala SS (85K garage queen)
'12 H-D FLTRXSE (36K parked)
'70 Pontiac Grand Prix Model J 400/TH400 survivor (103K)
#836745 - 11/15/10 03:20 AM Re: Replacing AC Evaporator and Heater core [Re: 1984_Z65]  
Joined: Nov 2010
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AreEyeSee Offline
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AreEyeSee  Offline
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Joined: Nov 2010
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Daytona Beach, FL
I've pulled out every bolt/screw possible trying to get the heater/AC box out and its not budging. Any suggestions or hints?


#837127 - 11/17/10 07:03 AM Re: Replacing AC Evaporator and Heater core [Re: AreEyeSee]  
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1984_Z65 Offline
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1984_Z65  Offline
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Wahiawa, Hawai'i
Originally Posted By: AreEyeSee
I've pulled out every bolt/screw possible trying to get the heater/AC box out and its not budging. Any suggestions or hints?



It wont come out like that.... pull the hood, and the right fender, remove the brace under the dash and ALL the surrounding hardware and it should come loose.

The side closest to the door moves out first, then the rest will slide out towards you. A large ortion is centered in the car and not straight in.

Removing the whole box versus just doing the evap and heater cores is a huge difference.


'84 SS 103K, '85 SS (Frame off)
'15 Silverado HD (Daily Driver)
'96 BBB Impala SS (85K garage queen)
'12 H-D FLTRXSE (36K parked)
'70 Pontiac Grand Prix Model J 400/TH400 survivor (103K)
#837385 - 11/18/10 04:57 PM Re: Replacing AC Evaporator and Heater core [Re: 1984_Z65]  
Joined: Dec 1999
Posts: 12,364
PB86SS/87LS Online beer
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PB86SS/87LS  Online Beer
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Joined: Dec 1999
Posts: 12,364
New Berlin, WI
FWIW when I removed the entire box on my SS I didn't remove the hood or fender. There is a connection or two behind the dash so to remove it properly, you will have to remove the dash.


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#837722 - 11/20/10 05:20 AM Re: Replacing AC Evaporator and Heater core [Re: PB86SS/87LS]  
Joined: Jan 2002
Posts: 762
1984_Z65 Offline
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1984_Z65  Offline
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Member

Joined: Jan 2002
Posts: 762
Wahiawa, Hawai'i
Originally Posted By: PB86SS/87LS
FWIW when I removed the entire box on my SS I didn't remove the hood or fender. There is a connection or two behind the dash so to remove it properly, you will have to remove the dash.


Come to think of it... When I replaced the Non-AC unit in my El Camino I didnt pull the fender either... just all cars after that I had the sheetmetal off the nose as it makes it easier to do....

You will have the AC controls, including the heater cable that has to come off, the vacuum hose connection, but I'm not entirely sure the dash has to come out either....

I dont have any spare g-bodies at the house to dismantle for the fun of it either.... frown


'84 SS 103K, '85 SS (Frame off)
'15 Silverado HD (Daily Driver)
'96 BBB Impala SS (85K garage queen)
'12 H-D FLTRXSE (36K parked)
'70 Pontiac Grand Prix Model J 400/TH400 survivor (103K)

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