‘72 Cutlass Air Conditioning Issues
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Joined: Nov 2016
Posts: 53
From: Davidson NC
‘72 Cutlass Air Conditioning Issues
Greetings Olds Fans, I need some expert advice on air conditioning. Yesterday we took a nice 200 mile round trip ride up to the blue ridge mountains. The first 30 or so miles the AC was blowing nice cold air, then for reasons unknown to me it the AC became less cold but still a little cool and the 4 speed blower fan switch seemed to stop working, even when I put it on vent. I continued our trip with it on VENT and after a while noticed the vent air felt pretty cold so i cut the AC back on and it was cold air again. On the return home trip similar occurrences of blowing cold AC and then not so cold. I could tell the compressor was running when idling by the drop in rpm on the tach. I also discovered that the blower fan switch seemed to not increase air flow on 2 did did increase on 3 and 4. I think something may be wrong with the blower fan circuit and would like to know if anyone can tell me how to trouble shoot this problem. Until yesterday the AC was working perfectly. Here in sunny NC with 90 degree days this old guy needs his AC cold. Thanks in advance for advice on troubleshooting this problem.
Oldsdruid
Joined: Dec 2007
Posts: 10,629
From: Southside Vajenya
My first thought is that the evaporator core is freezing up and cutting airflow thru it. If it does this again, switch to VENT, turn the blower to HIGH, and see if airflow picks up as the core thaws out.
This can happen on a very humid day, especially if the rubber peehole drain on bottom of the evaporator housing is plugged- and after nearly 50 years it probably is. Next time car is on a lift, fumble with that drain flap and see what kind of debris comes out. It will pop out if you need more access.
Sometimes if a system is either over or under charged they'll do this, or if the expansion valve is off adjustment.
Play around with your blower speeds to see if all work. If not, unplug the resistor and clean the terminals on both resistor and plug. A wire brush, fine sandpaper or contact cleaner in a spray can clean corrosion and grunge. Then some light grease on the terminals to prevent it.
This can happen on a very humid day, especially if the rubber peehole drain on bottom of the evaporator housing is plugged- and after nearly 50 years it probably is. Next time car is on a lift, fumble with that drain flap and see what kind of debris comes out. It will pop out if you need more access.
Sometimes if a system is either over or under charged they'll do this, or if the expansion valve is off adjustment.
Play around with your blower speeds to see if all work. If not, unplug the resistor and clean the terminals on both resistor and plug. A wire brush, fine sandpaper or contact cleaner in a spray can clean corrosion and grunge. Then some light grease on the terminals to prevent it.
Thread Starter
Registered User
Joined: Nov 2016
Posts: 53
From: Davidson NC
My first thought is that the evaporator core is freezing up and cutting airflow thru it. If it does this again, switch to VENT, turn the blower to HIGH, and see if airflow picks up as the core thaws out.
This can happen on a very humid day, especially if the rubber peehole drain on bottom of the evaporator housing is plugged- and after nearly 50 years it probably is. Next time car is on a lift, fumble with that drain flap and see what kind of debris comes out. It will pop out if you need more access.
Sometimes if a system is either over or under charged they'll do this, or if the expansion valve is off adjustment.
Play around with your blower speeds to see if all work. If not, unplug the resistor and clean the terminals on both resistor and plug. A wire brush, fine sandpaper or contact cleaner in a spray can clean corrosion and grunge. Then some light grease on the terminals to prevent it.
This can happen on a very humid day, especially if the rubber peehole drain on bottom of the evaporator housing is plugged- and after nearly 50 years it probably is. Next time car is on a lift, fumble with that drain flap and see what kind of debris comes out. It will pop out if you need more access.
Sometimes if a system is either over or under charged they'll do this, or if the expansion valve is off adjustment.
Play around with your blower speeds to see if all work. If not, unplug the resistor and clean the terminals on both resistor and plug. A wire brush, fine sandpaper or contact cleaner in a spray can clean corrosion and grunge. Then some light grease on the terminals to prevent it.
Thread Starter
Registered User
Joined: Nov 2016
Posts: 53
From: Davidson NC
Thread Starter
Registered User
Joined: Nov 2016
Posts: 53
From: Davidson NC
Rocketraider, I hope I’ve found the problem. I found the terminals on the fan switch resistor to be somewhat corroded. I cleaned with Corrison Block and a wire brush and so far the AC is working great. I’ve only driven it short trips since then but so far so good. I also checked the condensate drain hole and it was clear. I redid the heater core last year and had all that apart. I do need to get a new condensate drain hose. Classic Olds in Clemmons NC has them. Thanks for your advice. I appreciate you pointing me in that direction!
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