A/C wiring help
Thread Starter
|
Freshman User
Joined: May 2006
Posts: 44
Likes: 0
A/C wiring help
I have a 1979 F-100 with factory a/c. The a/c compressor has no power when the switch is turned on. It is a single wire and if I run to a positive it will come on. I was told it wont come on if there is no R-12, 134A, is this true? I was also told its a relay thats bad, went to the local parts store got a relay and I cant for the life of me figure out where it goes. Also cant find a good wiring diagram of the heat/ac unit anywhere. When I take the dash apart there is a green/white wire that runs to the one connection on the heat/ac controller that has no power at all. Is that an A/C wire? Does it go to this magical relay? PLEASE help.
Certified Thread Hijacker
Joined: Aug 2001
Posts: 14,441
Likes: 59
The first and best thing to do is to buy or borrow some A/C gauges and see if you have a full charge. Because the compressor WILL NOT turn on if the pressure is too low. No need to keep throwing parts at a problem that doesn't exist.
Josh
Josh
Senior User
Joined: Jul 2011
Posts: 270
Likes: 0
From: North West
Yes it does have a low pressure cut out. But if it's not energizing the compressor at all your system is flat and you will need to put it on a vacuum before you add any refrigerant.
Thread Starter
|
Freshman User
Joined: May 2006
Posts: 44
Likes: 0
Thanks for all the answers. One more problem I have not been able to get any help with. The center double vents in the dash, the duct work is completely gone on the top side. I have contacted several aftermarket companies and classic A/C companies with me getting the same answers "sorry we dont have those and don't know of anyone who does". Is there a possible fix that wont be jerry rigged.
Senior User
Joined: Jul 2011
Posts: 270
Likes: 0
From: North West
Trending Topics
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 784
From: Simi Valley, CA
One more problem I have not been able to get any help with. The center double vents in the dash, the duct work is completely gone on the top side. I have contacted several aftermarket companies and classic A/C companies with me getting the same answers "sorry we dont have those and don't know of anyone who does". Is there a possible fix that wont be jerry rigged.
Or are there two switches within a panel mounted into the dash to the left of the glove box that also contains two registers (Economy dealer A/C)?
People tend to confuse factory installed integral A/C with the two different types of dealer installed A/C, Deluxe and Economy.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Certified Thread Hijacker
Joined: Aug 2001
Posts: 14,441
Likes: 59
Josh
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 784
From: Simi Valley, CA
D3TZ-19B680-B .. Flexible Duct-Center Register to Evaporator / Obsolete
Applications: 1973/79 F100/350 & 1978/79 Bronco.
Sorry, no FoMoCo Dealer or obsolete parts vendor has any. AFAIK, not repro'd.
Cargo Master
Joined: Nov 2009
Posts: 2,364
Likes: 117
From: starship enterprise
my 79 factory air has no low pressure cut out and the ford factory seervice manual that I have SHOWS NO EVIDENCE of a low pressure cut-out from the factory, if the compressor has no power but the fuse panel has power for the ac fuse, it might be a de-ice switch. This is in the evaporator housing and has a capillary tube poked into the fins. Check for power here and see if the "fire" is coming in one side and out the other. if there is no "fire" here then the problem is more than likely in the control unit but the de-ice switches seem to fail before the control panel, they cycle more. Other than these two, the compressor is either on or off, no superheat or high pressure or low pressure that ford specs in their manuals and none that i've ever seen on a truck. you must have a good system to support 35* mine only gets down to about 39* on a 90* day on the highway.
Certified Thread Hijacker
Joined: Aug 2001
Posts: 14,441
Likes: 59
Josh
Thread
Thread Starter
Forum
Replies
Last Post
hoytenticer
1983 - 2012 Ranger & B-Series
5
Aug 6, 2024 12:13 PM
dlackey74
Explorer, Sport Trac, Mountaineer & Aviator
4
Dec 17, 2007 08:46 PM
classic79
1973 - 1979 F-100 & Larger F-Series Trucks
7
Apr 26, 2006 08:03 PM
