Automotive Air Conditioning Information Forum (Archives)

TexasEd on Wed September 28, 2011 12:54 PM

Year: 1969
Make: Ford
Model: Mustang
Engine Size: 302
Refrigerant Type: R12
Country of Origin: United States

I have a 1969 Mustang that was not a factory A/C car.
It had a dealer installed "Mark IV Custom" unit installed when new. This was a very cold A/C system that worked very well until age caught up with it. This is a family car that I just got from my brother. The A/C has not worked for a while and I don't know what if anything is wrong except that it is disconnected.

Here are some pictures:
Compressor and Dryer


Control Unit says "Mark IV Custom" under the glare at the bottom. The knob controlled temperature setting and the switch on the right controlled fan speed. The wire off the back seems to be tied into the thermostat. The knob has 2 terminal connections behind it for compressor on/off based on thermostat. The switch has 4 terminal connections behind it apparently for 3 fan speeds.



Evaporator housing with molded in vents. Control unit housing can be seen on the left with wires hanging out of it. There is a single eyeball vent on the drivers side at the same height. The entire housing can come out as a single piece.


All parts seem to be present including the Compressor, Evaporator, Dryer, Blower and Condenser. I don't know what works yet. The hoses and seals are probably all shot.

What can you tell me about it?
Is there a wiring diagram available for the control unit?
What are recommendations for restoring it to working condition?
What would an R134 conversion entail?

Thanks.

Edited: Wed September 28, 2011 at 12:57 PM by TexasEd

bohica2xo on Wed September 28, 2011 10:03 PM

The wiring should be color coded, and if it was working just re-connect it the way it was...

Getting it running again would require a new dryer and a leak check - if you keep it R12.

If you decide to go 134a, there is a bit more to do. The system will need to be flushed, the oil changed on the compressor & the condensor will need to be upgraded.

When you say that the A/C is "disconnected" do you mean electrically, or is there a hose off someplace? And why exactly was it disconnected? Noise? Poor cooling?

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

TexasEd on Thu September 29, 2011 12:36 AM

The wires are color coded but not the terminals in the back of the switches. There are also two gray and two redish-orange wires in the bunch.

I can't get a good answer on why it is electrically disconnected but it could be a lot of reasons. I need to trouble shoot the system.

Edited: Thu September 29, 2011 at 6:30 PM by TexasEd

ice-n-tropics on Sun October 02, 2011 6:47 PM

Ed
A good starting point for the lack of clutch power and/or blower function is the A/C on-off and lever action blower speed switch in the right side of the bezel.
If the blower switch incorporates the resistors, it must have air flow across the resistors to prevent overheating. If the bezel is unfastened and moved away during operation then the blower switch overheat and will fail. One failure mode is lack of power to the clutch via the rotary thermostat on the left.
Old IV Guy
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

bohica2xo on Sun October 02, 2011 8:03 PM

Tex:

Do you have a wiring diagram for this mk IV ? Sounds like he has a disconnected snakes nest. Only diagrams I have are OEM, with the TXV buried under the passenger hood hinge...


TexasEd:
Have you checked the system for pressure yet? If it still has positive pressure that is a good thing.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

ice-n-tropics on Mon October 03, 2011 10:32 AM

Brad,
My Mark IV service manual doesn't have the wiring diagram for this A/C.
Mark IV made crispy critters out of several air flow dependent resistor blower speed apps. before converting to multi speed motor windings. The photo shows what looks like resistors behind the right corner of the rectangular louver (which I designed for the Mark IV Monitor dual louver under dash evap.).
Typically the blower switch incorporated the on/off power to the thermostat/clutch circuit.
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

mk378 on Mon October 03, 2011 1:56 PM

Find the blower motor and see how many wires it has. A one or two wire motor will be a resistor type system (one live wire and possibly one ground, or internally grounded). Motors with 3 wires are multi-speed. Each wire goes to a terminal on the switch, and one at a time is powered depending on the speed selected. There may also be a ground wire or the motor could be internally grounded.

If you have the switch test it with an ohmmeter to see which terminals are connected at each position. There's going to be a live wire, a compressor wire that is connected to the live wire in all positions except off (this feeds the thermostat, and then on to the compressor), and 3 motor wires for the multispeed motor, one at a time being connected to the live wire. If it's a resistor system there'd be resistor coils on the back of the switch and only one motor wire.

TexasEd on Mon February 20, 2012 2:35 PM

Thanks for the replies. I had not worked on this in a while.

- I don't think there is pressure in the system

mk378, Thanks for the advice on checking the blower motor. I'll look at that. I'll take a picture of the back of the controls if that helps.



Thanks,
Ed