1979 Mark V Collector’s Series AC Question & Follow Up….

Hello Bill –
I have a 1979 Lincoln Mark V Collector Series and my A/C seems to come in and out during acceleration? Sometimes it seems like the air is blowing, sometimes it’s not blowing and the air is warm or hot coming in through the vents? Any info you have on a problem like this? It seems really weird that it seems connected to the acceleration? The a/c works great when the car is just idling, no loss of power at all?!!!
Thanks
Ron K.
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Hello Ron –
You are correct. The problem is showing up for you on acceleration because the system is designed to default to heat and full defrost in the event of vacuum loss. Acceleration under load reduces vacuum. When you have a small vacuum leak or a check valve failure etc. the system will drift towards heat until the engine vacuum stabilizes again when you release the pedal. We have addressed this issue several times on the blog and you should be able to navigate to these earlier replies. They all explain that having a vacuum diagram on hand is the best way to diagnose the problem. If you need such a diagram or referral to the previous posts please contact our office. Good luck on an easy repair.
Sincerely,
Bill
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Bill –
Thank you for your insight into this problem and pointing me in the right direction. I will need to get 1 of those vacuum diagrams and start the process of elimination. I’m glad I found you and look forward to learning about this wonderful piece of “art” and passing it on to my sons, so they too, can help preserve a piece of America’s automobile history.
Thanks Again,
Ron
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Hi Ron –
Thank you for your courteous reply. What you have thanked us for is exactly what the Lincoln Land blog is all about. We want to help provide our customers with an insight into their sometimes difficult Lincoln issues and point them in the right direction to the correct diagnosis and repair. I always emphasize that the proper literature and some understanding on any given problem are two of the most important tools in any automotive workshop. With that and the information that we post many Lincoln owners can learn to uncover and repair some of the issues that develop in vehicles over the years.
Sincerely,
Bill