AC Box Seal
- Thread starter ES1
- Start date
This is actually a common area for water leaks.
After owning many G bodies, there are somethings I learned to take into consideration.
The box is sealed to the firewall with a soft foam seal and then GM sealed over it with seam sealer that would get petrified and crack. On some of the cars I have had, this would allow water to run down the windshield, under the lower molding and into this crack. Water would sit there and rot/rust out the opening in the firewall and then the passenger side floor pan. My 78 Malibu was like this.
On a lot of the 1980 and newer A/G bodies equipt with computer controls for the engines, there is a approx 2" diameter hole bored into the lower portion of the heater/ac box for the wiring harness to run through. The position GM had the wires on some cars would allow water to enter the passenger compartment and rust out the floors. Here is what happens. When it rains, water will overflow the channel at the base of the windshield. It runs over the edge and down on to this harness. On some cars, the tape doesnt run all the way up to the rubber firewall grommet. Water leaks in between the wires and into the cars. Ask me how I know this?
The last source for leaks is internally on the box. I have observed several cars with leaks coming from the corner of the box that hangs over the passenger side floor. You will find that GM didnt install sealant on them and on others, they used dum-dum or butyl tape to seal it.
Keep in mind that you can over flow the box if your evaporator drain becomes blocked with leaves or other debris. I suggest removing the inner fender well and lifting the rubber flap at the bottom of the box and cleaning it out thoroughly.
While the fender well is out is also a good time to check out the seal/seam sealer around the box. Make sure you check the top really well as this is where the firewall will rot and if it is rotted, you will have to pull the dash and the box out of the car.
After owning many G bodies, there are somethings I learned to take into consideration.
The box is sealed to the firewall with a soft foam seal and then GM sealed over it with seam sealer that would get petrified and crack. On some of the cars I have had, this would allow water to run down the windshield, under the lower molding and into this crack. Water would sit there and rot/rust out the opening in the firewall and then the passenger side floor pan. My 78 Malibu was like this.
On a lot of the 1980 and newer A/G bodies equipt with computer controls for the engines, there is a approx 2" diameter hole bored into the lower portion of the heater/ac box for the wiring harness to run through. The position GM had the wires on some cars would allow water to enter the passenger compartment and rust out the floors. Here is what happens. When it rains, water will overflow the channel at the base of the windshield. It runs over the edge and down on to this harness. On some cars, the tape doesnt run all the way up to the rubber firewall grommet. Water leaks in between the wires and into the cars. Ask me how I know this?
The last source for leaks is internally on the box. I have observed several cars with leaks coming from the corner of the box that hangs over the passenger side floor. You will find that GM didnt install sealant on them and on others, they used dum-dum or butyl tape to seal it.
Keep in mind that you can over flow the box if your evaporator drain becomes blocked with leaves or other debris. I suggest removing the inner fender well and lifting the rubber flap at the bottom of the box and cleaning it out thoroughly.
While the fender well is out is also a good time to check out the seal/seam sealer around the box. Make sure you check the top really well as this is where the firewall will rot and if it is rotted, you will have to pull the dash and the box out of the car.
- Joined
- May 28, 2001
To get it sealed properly, the top of the box should be removed, the petrified sealer cleaned off, the condensate drain cleaned, and the lid resealed. Pay close attention to the area where the lid seals to the firewall.
A day's job.
A day's job.
