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I got my blue Hummer (well, it's my wife's Hummer actually) back from Medved earlier this week with Dale's heater "modification" in place. WOW....the heater now cranks out some SERIOUS heat. They measured it at 150 degrees. My wife can now drive around in comfort at night when the temperature goes down into the single digits here. In fact, on the way home from Medved, my kids were sweating so badly that we had to turn the heat WAY down.

It's not a modified bracket or valve as I thought earlier, but simply a realignment of the diverter door inside the heater box. It's a tin plate with rubber seals around it. Apparently it was not closing all the way which allowed fresh (read cold) air into the system. The heater was doing it's job, but the warm air was cooled by the outside air before it got to the cabin.

I'm looking into the effect on the A/C with this "realignment" but on a recent "warm" day, the A/C seemed to actually blow colder than it ever has. It could be that the realignment of the door also helps the A/C for the same reason. The cool air is warmed up by outside air allowed into the system by the partially open door.

It doesn't seem to affect the defroster however. It seems that I "got lucky" with my green Hummer since I have absolutely NO problem getting the fog off my windshield and side windows on that one, but the blue wagon still has a bit of a problem. It's slightly better, but not as good as our green Hummer.

I'm still looking into it and I'd like to get some photos of exactly how the realignment is done, including before and after photos of the door positions in various modes. I've asked that Dale let us take some photos of the procedure on the next heater box that he opens up. Dave Breggin, get your digital camera ready!

I know that Dale has shown this to AMG and I'd like to hear their response as well.

Kevin S. Beebe

I have taken the liberty of sending you these pictures of the modifications I made on our '96 heater. A lot of the low air volume seems to be caused by pinched hoses in the floor driver vent and around the heater assembly on the right. I hope this may be of some help.

John W. Watkins Jr.

(click on any photo for the larger version)

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