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I’m installing factory original air conditioner/heater in 1979 Ford F250 that did not originally come with air conditioning. I obtained used components: evap/heater core box at firewall, plenum/mixing box, ductwork, vents, and controls. I’ll be using a Sanden rotary compressor instead of the original York piston compressor. I’m using R-134a compatible condenser. I’m replacing evaporator, heater core, and blower. My questions are about the 8-port vacuum switch, the controls, and the vacuum motors.
1. What is the difference between these two 8-port vacuum switch valves; 1-contact versus 2-contact? What is the function of the 2 contacts? How can both be for the 78-79 Bronco as listed on Dennis Carpenter?
- D8TZ-19B888-A Vacuum Switch Valve - 1 Contact - 1978-79 Ford Truck, 1978-79 Ford Bronco
- D5TZ-19B888-A Vacuum Switch Valve - 2 contact - 1973-77 Ford Truck, 1978-79 Ford Bronco
2. I have the later version ac/heater controls (without the cursive “Air Conditioning” text). Does it matter which vacuum switch I use (1-contact or 2-contacts)?
3. Are there differences in the mixing boxes and the vacuum motors? Do some of the early vs later boxes use vacuum motors with different number of vacuum lines to the vacuum motors (one versus two)?
Last edited by kpierson777; Aug 6, 2025 at 09:54 PM.
Reason: Correction
Side note: test the blower motor to be spinning in the correct direction. I hear that some times the 2 wires (orange/white?) can be backwards on repop motors and if you go color to color it MIGHT spin backwards. And once it is all in that is NOT the time to find that fact out.
I just dug out my spare switches tonight. And I have all the vacume line stuff you asked about. So like the 3 and or 8 port stuff. I will try and contact (call you) you tomorrow afternoon. Here are some diagrams and info for ya. Too bad this link is dead. http://www.rowand.net/Shop/Cars/1979FordF100/AC.htm AWESOME info place with lots of a/c pics.
