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1996 Seville STS
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Hello, And thank you in advance for any input...

I have hot air from pass side of car BUT warm almost cool air from drivers side at top and bottom. top when set to defrost and bottom when set to Auto/Econ the TEMP and or other setting do not change the fact I get hotter air from pass side VS driver side.

Ok 1991 Deville, new 195 deg themostat, new heater core(flows fine) new 3 way heater tube value(thingie). I have replaced most of the parts that I could that would cause a problem since I was in there already.

Other things I have checked are Vacuum to the box (name?) with mixture door motor in it traced down the lines to the motors ...good. Checked mixture door VS the temp setting it moves with temp changes.

The Heater core is very hot when Mixture control box and cover are removed and air does blow thru core very well.

Something I'm not understanding are that with heatercore access part removed the access door on backside has a part made into it that looks as it could be used to split the output of heater core to top and bottom, when looking into heater/AC unit there is a split lower side goes to drivers side upper to pass side.

I have followed the lower tunnel to the center drop down duck work for heater and the upper to rear of drop down duckwork for heater. If I aplied vacuum to the blue vac line I even had poor heating out drivers dash vent, without feeling anymore temp mixture doors in the drivers side ducking.

I did this wondering if system was split for dual driver/pass cooling heating settings. With the hopes of finding a door closed off since the cooling works fine. but I have no controls for a split system and now no clue where else to look short of Pulling to entire thing out and making it work the way I want it too on the floor and then putting it back in :bonkers:


Jim
91 Deville
 

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I'm having the exact same problem in a newly purchased 94 deville. Anyone out there have any ideas??? Pass side, puts out hot air, drivers side very cold.....

Any help would be great!!!

Thanks in advance!
Ryan
 

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'05 Expedition
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That's a weird one. The only heater air flow box I've ever taken apart was from a '64 Comet, so I may not be much help. If the air is hot on the passenger side, I don't think you have a cooling system problem. Instead you have an air flow problem with one of the diversion valves.

Maybe, like you said, you'll have to pull the box out and inspect it. There is a valve in there that directs air over the hot coils and then it releases it out to the floor. On cars without electric thermostats, this door is manually controlled by a cable connected to that blue/red lever thing.

Maybe that door is not getting completely closed because theres a twig or a leaf impeding its movement. Some of the air from outside gets diverted over the heater core, some does not. This would explain why some of the air is hot, and some is warm.

I think that on Cadillacs there are little motors that control the valves and regulate the temperature of the air entering the cabin. One of these motors may be failing (if there are such things).

Try this: If your control panel allows it, manually divert the "hot" air out of the A/C vents. See if the air is hot on both sides. Also try manually diverting the air out of the windshield defroster. It should be hot on both sides.
 

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I can't manually divert the air out the a/c vents, but on defrost, it does still put out cold air on the drivers side vent under the windsheild, and hot air on the pass. There must be a door stuck somewhere. Anyone know where it is located?

Thanks in advance!!

Ryan
 

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rmoen said:
I can't manually divert the air out the a/c vents, but on defrost, it does still put out cold air on the drivers side vent under the windsheild, and hot air on the pass. There must be a door stuck somewhere. Anyone know where it is located?

Thanks in advance!!

Ryan
im a mechanic working on a 91 deville and i have the same problem. hope we can get the fix found
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02 eldo collectors series, 98 eldo, 97 deville, 96+94 SLS,
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Hey I have a 93 deville, and I am pulling my hair out over here, I have the SAME EXACT problem with mine!! I have been trying to figure this one out for a long time, I have owned 9 Caddy's and this is the only one I have ever seen like this aside from you fella's, if you guys figure anything out please lemme know, I have a 500 mile trip with my wife and 3 month old baby to do in December (military relocation) and can't do it with bad heat, if I find anything I will let you guys know ASAP.


Thanks, Jack
 
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