Heating issue

[94_SDV]

First issue with my new toy, I've got a 94 Sedan DeVille (4.9) and the climate control works, but the heat only dribbles out, even though the fan is going full blast. Even when I set the fan to "hi", and you can hear it working, the heat doesn't blow very hard and never reaches the interior temp I set it for. The coolant is full and gets to normal temperature quickly. Anyone have any thoughts?

[Ranger]

Look for cracks or holes in the plastic HVAC housing on the firewall.

[94_SDV]

And what does the HVAC housing look like? Sorry, newbie without service manual here, first Cadillac

[Ranger]

It's a big plastic housing bolted to the firewall. The blower motor is mounted on it.

[94_SDV]

Thank you, Ranger. Would it be a problem with whatever is in the plastic housing, or should I concentrate on the plastic housing itself? If it is cracked housing, how do I fix it?

[Ranger]

Most likely you'll find a hole in the housing. It gets brittle and starts breaking apart, thus most of the air from the blower motor is escaping under the hood, leaving low air flow to the cabin. Unfortunately, I think the only way to replace it is to drop the motor. There have been discussions in the past with some innovative ways to repair it, like self stick drywall mesh tape and then slather it with silicone. The problem is, the rest of is is very brittle as well. First thing to do is check and see if that is your problem.

[94_SDV]

Thanks very much for your advice, Ranger. I will check it tomorrow morning.

[4.9 Guy]

The heater core could also be clogged. I had that problem last winter, and it was a pain in the ass.

[Ranger]

A clogged heater core would restrict coolant flow and affect temperature, but would not affect air flow.

[94_SDV]

Okay, the plastic housing separated from itself right on the top and when I put my hand over the hole, all I could feel was air! I siliconed it so when it dries I'll test it out. Thank you, Ranger!

[94_SDV]

I tested the climate control this morning and the air pressure is beeter, but no where near where it should be. It's also not as hot as it should be, so perhaps a new heater core is required. I'll have to check and see if there are more cracks in the HVAC housing. Does anyone know how to "force" the air to come out of the front vents, rather than the floor and/or windshield?

[Ranger]

There well may be more cracks. Check it closely.

You cannot change the air flow. Heat comes from the floor and cooling comes from the dash vents, period. The Devilles did not get a mode button till 2000.

[94_SDV]

Nothing like "no choice" to help you make up your mind. I'm glad I asked or I would have spent a lot of time trying to figure it out. I will check for more cracks, I'm guessing there are some more. Thanks, Ranger. Much appreciated.