'73 A/C system questions
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Laughing Gas
Joined: Jan 2004
Posts: 913
Likes: 2
From: Pensacola, FL
'73 A/C system questions
got a couple of questions about my '73's a/c.
first, my blower switch doesnt have an off selection, it has low, then 2 dots that represent med-lo, med-hi, and high....is this normal?
second, how do you turn the system on, because i dont see anything that looks like it cycles the compressor on or off, or sets the temp limit at which it comes on automatically.
sorry for the freshman questions, never had ac in a vehicle this old before, and would like to get it working.
thanks.
first, my blower switch doesnt have an off selection, it has low, then 2 dots that represent med-lo, med-hi, and high....is this normal?
second, how do you turn the system on, because i dont see anything that looks like it cycles the compressor on or off, or sets the temp limit at which it comes on automatically.
sorry for the freshman questions, never had ac in a vehicle this old before, and would like to get it working.
thanks.
Tuned
Joined: Aug 2003
Posts: 346
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From: Eastern Virginia
These 70's trucks with A/C had no "off" position for the blower. The blower automatically comes on when the bottom selector swithch is moved to any position. It is a 4 speed fan. The top selector is just a blend lever. Move it to the left toward "cool" and the door to the heater core is shut off. Move it toward "warm" and the blend door opens to the heater core. A/C trucks also have a heater control valve. When the top temperature selector is all the way to the left at "cool" the coolant flow to the heater core is shut off. Move it about an inch toward the right toward "warm" and coolant begins to circulate through the heater core. The A/C compressor comes on with the bottom selctor in the A/C position. If you have an owners manual it goes into a lot more detail on the "climate control" system. By the way, nothing in this system is automatic like the newer vehicles. Surprisingly the A/C system and heater in my '75 F150 work quite well and efficiently for a near 30 year old vehicle. However my non-A/C '74 F100 leaves MUCH to be desired.
Postmaster
Joined: Feb 2003
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When the lower lever is at "off" as you have it in the picture the blower will shut off. I can't read the 2 middle words. It looks like a factory AC panel since it says "air conditioning" on it but your panel is different than my 76. Probably the best thing to do is start the truck then select different settings on the panel then open the hood and watch the compressor. The lower level controls where the air comes out as well as functions like AC and heat. 'Vent' should blow out the dash registers, 'heat' blows on the floor, 'Def' blows at the windshield.
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Laughing Gas
Joined: Jan 2004
Posts: 913
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From: Pensacola, FL
well, 2 and a half months later, i finally got time to start messing with it, and here is what i found.
if i take the lead from the compressor to the battery, the clutch engages, so i know that much works.
i found a weird little thing that is close to the condenser, and cant identify it, also it has a plug on it, but is not hooked up. i think i found the wires that go to it, and the compressor, but when i hook it up, and go through the selections on the dash, nothing happens.
i still cant figure out which control on the dash actually turns on the compressor. i know off is off, but cant figure it out from there.
any help would be greatly appreciated. i posted pics in the gallery of the new little piece that i found, so if you can identify it that would be great.
thanks
if i take the lead from the compressor to the battery, the clutch engages, so i know that much works.
i found a weird little thing that is close to the condenser, and cant identify it, also it has a plug on it, but is not hooked up. i think i found the wires that go to it, and the compressor, but when i hook it up, and go through the selections on the dash, nothing happens.
i still cant figure out which control on the dash actually turns on the compressor. i know off is off, but cant figure it out from there.
any help would be greatly appreciated. i posted pics in the gallery of the new little piece that i found, so if you can identify it that would be great.
thanks
Fleet Mechanic
Joined: Sep 2003
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From: savannah,ga
just saw thisthread
the switch on the far right is the ac control
the switch on the right is heater and defrost only
my 76 e-150has the same set up
ac is totally separate from the factory system
the fan and clutch are controled by the right hand switch with its own electrical
system. fan is under the dash
the switch on the far right is the ac control
the switch on the right is heater and defrost only
my 76 e-150has the same set up
ac is totally separate from the factory system
the fan and clutch are controled by the right hand switch with its own electrical
system. fan is under the dash
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Laughing Gas
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Joined: May 2001
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From: Rhode Island
I dont know how it works for the older trucks, but my dad was having problems with his a/c in his 94 ranger. His compressor would not turn on until he had his system completely full of r-134. Is your system charged? completely? just a thought.
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Laughing Gas
Joined: Jan 2004
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From: Pensacola, FL
well, i am not really sure, i know that problem though, had it on my '96 windstar, it is a pressure switch. the main thing i need to know is how the system is actuated on and off, because i have an a/c and max a/c switch in the van, but nothing like that in the truck.
Tuned
Joined: Aug 2003
Posts: 346
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From: Eastern Virginia
Hmmm....That's a bit different than my '75 F150. On my '75 it says "Off, Vent, A/C, Panel, Floor, Defrost" with 2 down arrows between the latter 3 for mixing. My best guess would be trying "panel". But on my '75 "Panel" just lets air, warm or cool, blow from the dash vents only. I use panel in the winter to get some heat up high quick. I don't think you have a low pressure cut-out switch. The only switch my '75 has besides the dash switch is the evaporator cut-out in the evaporator. This senses the evaporator freezing and cuts out the compressor. It shouldn't prevent the compressor from engaging regardless of the pressure unless it's busted. When that old York compressor kicks in, you'll know it.
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Laughing Gas
Joined: Jan 2004
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From: Pensacola, FL
maybe it is a mis label on the control panel. not sure, gonna try to get a chance to run down the wires in a couple of weeks and see where everything leads back to.
71LTD390, i have what i think is a switch in front of the radiator support that i suspect is for the evap. cut out. could you take a look at my gallery and let me know.
thanks,
jamie
71LTD390, i have what i think is a switch in front of the radiator support that i suspect is for the evap. cut out. could you take a look at my gallery and let me know.
thanks,
jamie
Tuned
Joined: Aug 2003
Posts: 346
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From: Eastern Virginia
The evaporator cut out switch is in the evaporator under the dash. I don't exactly know what that is in the picture. My best guess is a plug for an engine block heater or something. Trace the wires and see what you come up with.
Senior User
Joined: Jul 2004
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From: Corpus Christi,Tx.
First time post... hope it helps.
I have the owners manual from my '73 F100 (covers 100 - 350).
The A/C compressor should run if the selector is in the panel or the dot between the panel and floor position only.
The compressor in mine engages (no cool air ... yet) unfortunatly my engine is in pieces so I can't confirm what the owner manual states.
Mine has the little thing in front of the radiator support... if you unplug it the compressor won't run ! Shoot, I was halfway expecting the thing to light up when the compressor is on. mine has a red circle in the center of it.
Tony
I have the owners manual from my '73 F100 (covers 100 - 350).
The A/C compressor should run if the selector is in the panel or the dot between the panel and floor position only.
The compressor in mine engages (no cool air ... yet) unfortunatly my engine is in pieces so I can't confirm what the owner manual states.
Mine has the little thing in front of the radiator support... if you unplug it the compressor won't run ! Shoot, I was halfway expecting the thing to light up when the compressor is on. mine has a red circle in the center of it.
Tony