High speed fan relay, wiring update
I have been working on updating the wiring on a-body AC system. Tried to use quality parts that are reasonably priced and available.
Mopar push button vacuum switches come in a few types. What I used for the wiring update was the later / re-pop style. This five button switch has three lugs off to one side and two lugs in the center.
The earlier push button switch has two lugs off to one side and two in the center. My update wiring will not work with this style. Because one of the lugs power turns on and off with the depression of the ac buttons.
Also I have found that the wafer boards on the inside of the vacuum push button can fail and cause ether the vacuum part or the electrical switch part to not operate properly.
Updating your original wiring is well worth the money spent. Old wiring can cause your car to burn up.
These are my bench test readings:
12V+ in
Low speed Heat & AC 4.5 amp draw
Med speed Heat & Defrost 5.5 amp draw
Med speed AC 6.8 amp draw
High speed Heat & Defrost 6.2 amp draw
High speed AC 7.2 amp draw
A-body AC blower motor wiring update info.
Re-use the original vacuum switch and fan speed switch. Check that they are in good condition, look for loose rivet corrections.
Adding two relays, like the diagram, will remove the electrical load when the blower motor in high speed.
This set up keeps the original five blower speeds.
New / available blower motor resistor.
Parts:
Hella Relays
4 pin part # 965400001
5 pin part # 933332661
Blower motor resistor # RU 96
Blower motor resistor connector BWD # PT 5692
Ford standard box terminals available @ Mouser part # 571-1438238-9
Wire info:
18 ga wire good for 3 amps
16 ga wire good for 6 amps
14ga wire good for 15 amps
12 ga wire good for 20 amps
I have been working on updating the wiring on a-body AC system. Tried to use quality parts that are reasonably priced and available.
Mopar push button vacuum switches come in a few types. What I used for the wiring update was the later / re-pop style. This five button switch has three lugs off to one side and two lugs in the center.
The earlier push button switch has two lugs off to one side and two in the center. My update wiring will not work with this style. Because one of the lugs power turns on and off with the depression of the ac buttons.
Also I have found that the wafer boards on the inside of the vacuum push button can fail and cause ether the vacuum part or the electrical switch part to not operate properly.
Updating your original wiring is well worth the money spent. Old wiring can cause your car to burn up.
These are my bench test readings:
12V+ in
Low speed Heat & AC 4.5 amp draw
Med speed Heat & Defrost 5.5 amp draw
Med speed AC 6.8 amp draw
High speed Heat & Defrost 6.2 amp draw
High speed AC 7.2 amp draw
A-body AC blower motor wiring update info.
Re-use the original vacuum switch and fan speed switch. Check that they are in good condition, look for loose rivet corrections.
Adding two relays, like the diagram, will remove the electrical load when the blower motor in high speed.
This set up keeps the original five blower speeds.
New / available blower motor resistor.
Parts:
Hella Relays
4 pin part # 965400001
5 pin part # 933332661
Blower motor resistor # RU 96
Blower motor resistor connector BWD # PT 5692
Ford standard box terminals available @ Mouser part # 571-1438238-9
Wire info:
18 ga wire good for 3 amps
16 ga wire good for 6 amps
14ga wire good for 15 amps
12 ga wire good for 20 amps