A/c Problems

masonjar · Jul 29, 2017

HiYa: My A/C works great for about an hour then will blow the cold air somewhere else. Sounds like some vent opens and directs the cold air outside. The fan switch also gets hot and I need to replace it about ever other year. My car is black so it does get hot during the summer. Help is helpful. Thanks.

Mustang5L5 · Jul 29, 2017

Losing vacuum to the hvac system that controls the vents?

General karthief · Jul 29, 2017

Symptoms are similar but parts are different between years, would help to know what year the car is.
Switches getting hot are encountering resistance at a connection, there is a resistor thing that controls fan speed and vacuum lines that control floor, defrost and dash vents. Check the electrical connections for loose or discoloration and your vacuum lines for split, cracks and broken connections.

masonjar · Jul 29, 2017

All the vacuum hoses are in good condition and I hear no sucking leak. The engine never changes like you might expect with a leak. And why after the engine is hot for so long? Driving down the road enjoying the cold air and then suddenly the air starts to flow elsewhere.

masonjar · Jul 29, 2017

karthief said:
Symptoms are similar but parts are different between years, would help to know what year the car is.
Switches getting hot are encountering resistance at a connection, there is a resistor thing that controls fan speed and vacuum lines that control floor, defrost and dash vents. Check the electrical connections for loose or discoloration and your vacuum lines for split, cracks and broken connections.

masonjar · Jul 29, 2017

1990 Mustang GT HatchBack. it is in my post. And I am checking these things today. I have not found anything except a slightly burned fan switch.

General karthief · Jul 29, 2017

masonjar said:
HiYa: My A/C works great for about an hour then will blow the cold air somewhere else. Sounds like some vent opens and directs the cold air outside. The fan switch also gets hot and I need to replace it about ever other year. My car is black so it does get hot during the summer. Help is helpful. Thanks.

Didn't see the vehicle discription in there but I am on a kindel and don't see the bottom lines.
If you are burning up switches the problem is at the connection or down stream, go to veryuseful.com for wiring diagrams for your stang. Check connections and do resistance testing.
You may need to hook up a vacuum gauge to your hvac lines one at a time and drive it around to see where your losing vacuum.

masonjar · Jul 29, 2017

karthief said:
Didn't see the vehicle discription in there but I am on a kindel and don't see the bottom lines.
If you are burning up switches the problem is at the connection or down stream, go to veryuseful.com for wiring diagrams for your stang. Check connections and do resistance testing.
You may need to hook up a vacuum gauge to your hvac lines one at a time and drive it around to see where your losing vacuum.

All right. I have never heard of veryuseful.com before. I will try it and see. Thanks

jrichker · Jul 30, 2017

The following are diagrams courtesy of Tmoss & Stang&2birds

Vacuum diagram 89-93 Mustangs

Fuse box layout
HVAC vacuum diagram

masonjar · Jul 30, 2017

jrichker said:
The following are diagrams courtesy of Tmoss & Stang&2birds

Vacuum diagram 89-93 Mustangs

Fuse box layout
HVAC vacuum diagram

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring; http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

*********************************
Wow! Thanks for taking the time for this. I have not found the problem yet so I know what I will be doing later today. I hate working under the dash.

masonjar · Aug 10, 2017

Well I did not find the problem on this I got side tracked on a ball joint that had lost it's cotter pin and became lose. But I was wondering if excess condensate in the unit would cause problems such as this. I went on a twenty minute drive and then watched the water drip for hours under the car and it was alot more than I would expect. Also I do have fog that comes out of the vents at times which is just water I suppose. And now I am wondering if the drip hole is clogged. I will check on that soon. Thanks again.

jrichker · Aug 10, 2017

What is the coolant level doing? A leaky heater will cause a drip from the condensate drain line.

masonjar · Aug 10, 2017

I have lost a bit of coolant since I have had this car but I do not think it leaks at the heater coil. There are no leaks inside nor do I smell that odor nor does the windshield get that slimy fog on it. And what leaks out is just clean water.
EDIT: I do have a small oil leak that winds up at the base of the distributor so coolant might leak there also. I do not know.

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