Condensation from heat vents

[MRP78]

I took an 87 GN for a ride yesterday. It was cool outside in the low to mid 40s. Once it reached normal temperature (I believe this car has a 160 t-stat) I turned on the heat and it looked like it was blowing dust out of the vents so I turned the fan on high, but it kept doing it. It looked like mist from a humidifier. The air was not warm and didn't smell like antifreeze but did fog and steam up the windshield. I turned it to defrost but it didn't seem to help or make it worse and no steam appeared from the defrost vents. Where should I start? It looks like it has the original heater control valve but it's very corroded on the outside.

 

[Rich Gio]

Heater core. Bypass the core with length of hose and try it again.

 

[salvageV6]

If there is anti-freeze in the radiator it should smell a bit like that.

Otherwise check the heater box itself for a leak from the outside or perhaps the inside too.

Even if I had to open up the plenum box I'd have a new heater core on hand just in case......

 

[MRP78]

Would a bad heater control valve cause the same problem or how could I tell if its the heater core or control valve or both?

 

[Rich Gio]

I don't think the control valve would cause that. All it does is control the amount of water you have flowing thru the heater core.

 

[MRP78]

Where do I get a replacement core? I can't seem to find a vendor that has them or online elsewhere. GM 52479872 or AC Delco 15-60026. I read the ones from a local auto parts store are wrong and don't fit right.

 

[Rich Gio]

http://www.gbodyparts.com/product_info.php?products_id=523&osCsid=2e2488e8b6c81dfcf417b5ba53f43798