I'm doing some planning on how to install a 1996 5.8L I pulled out of a E250 in my 1977 F100 that currently has the original 5.0L.

The 5.8L has been rebuilt and carbed. I'm using the serpentine system that came with the 5.8L when I pulled it at the junkyard.

There are several systems I need to retrofit to install the motor (4G alternator, power steering, electric fuel pump) but I'm trying to understand what I need to keep from the 1977 air conditioning system and what I should replace/add with more modern components.

As you will see from my questions I don't know much about air conditioning systems other than what I read from my '77 shop manual and figured out looking at online stuff on the newer systems.

The truck has factory air. The current system has lost its freon. I'm not sure where the leak is and I'm probably not going to try and figure it out at this point. The blower motor is squeaking and I need to open up the evaporator housing to fix that. I'm going to clean it out and clean the heater core and evaporator at the same time. I've found some online guides that will make that a bit easier.

This is what I'm planning to do, and a couple questions I have. Any insights or suggestions would be greatly appreciated.

• I'll be using a '96 sanden compressor and clutch.
• I'm planning on fitting a '96 F150 condenser in place of the stock unit that was designed for an R12 based system.
• I'll have to use the original evaporator to fit in the big firewall A/C-Heater box. I'm going to pull it, clean it, check it for leaks and flush it well. If it has a leak I can get a replacement from LMC ($$) unless I can get it repaired somehow.
• I can see that I'm probably looking at getting a set of custom hoses made.

Now for a few questions.

• Should I use the '77 expansion valve or try and fit one from a '96 truck?
• Does it matter if I use a new '77 receiver drier or do I need to use a receiver drier accumulator from a '96? The '77 unit sits at the condenser and it looks like the '96 one sits at the evaporator outlet. I'm not sure the '77 unit will attach to the '96 condenser without an adapter fitting, and same thing for the '96 unit attaching to the '77 evaporator.
• Do I need to fit an orifice tube in the evaporator high side line? I'm not sure, but I don't think the '77 system has one.
• The '96 system has an inline filter (between the compressor and the condenser?) that the '77 system doesn't have. Would it be a good idea to try and fit one in the system?
• Anything else I should think about?

Thanks for any advice you can give me.

 

That sounds good.

A bit of background first. In the 1960's and well into the 1970's, when you turned on the A/C, the compressor ran continuously. They had the storage and drier function on the high side (a Receiver/Drier). Because the compressor ran continuously, a means had to be provided to modulate the amount of heat transferred, or else the evaporator would freeze up in a low cooling need situation. So they used things like a STV (Suction Throttling Valve) to do that function.

Next, to improve fuel economy, many went to the fixed-orifice systems, that cycle the compressor ON-OFF when the A/C is ON. That type of system has a fixed orifice tube at the inlet (high side) of the evaporator. At the outlet of the evaporator is an Accumulator/Drier. Sticking into the Accumulator/Drier is a Cycling Pressure Switch. This switch has multiple functions:
First, it senses if the pressure is too low in the system (like low on charge, or cold weather below about 32-35 degrees or so), the CPS will be open, preventing the compressor clutch from engaging.
Second, this low pressure opening of the CPS switch is also used to drop out the compressor in a cooling cycle to avoid evap freeze-up. When the switch opens, the compressor clutch drops out, the system warms up until a trigger point some degrees higher than the minimum, then it closes again, starting the compressor. There is a difference between the two pressure (temperature) switch set points to avoid it chattering on-off-on-off.

If I were doing it, I would go with the fixed-orifice system, and acquire parts from a target vehicle to do that. You will need a place to connect an orifice tube. In most Ford systems, the orifice tube itself is inserted into the inlet (high-side) of the evap. However, some GM vehicles have the orifice in a separate tube that is then attached to the evap inlet, and there are repair kits for Fords, etc. that put an orifice into a piece of tubing that is then attached to the evap. Just need to get it as close as possible to the evap inlet, as the pressure drop after the orifice is what starts to absorb heat, and don't want that absorbing much under-hood heat, or else you lose some cooling capacity.

No. It's not a filter, if it is an integral part of the high-side hose assembly, it's a muffler, designed to quiet down the sound of pulses of hot gas from the cylinders of the reciprocating compressor. I've had FFOT (Ford Fixed Orifice Tube) systems from earlier years that did not have a muffler. It's just a little louder "compressor sound" without the muffler.

There are other systems, like TXV (Thermostatic eXpansion Valve) that work well, but they need a means to sense that the evaporator is nearing freezing, done by a capillary tube switch, or by a thermistor sensor connected inside the evap fins. These open a relay that drops out the compressor. To do one of these would require the most work and figuring out and selecting parts by specifications. They use a Receiver/Drier on the high side.

Good to see that you are going to use a R-134a designed condenser, that is a wise move.

Oh, one other thing, for R-134a, need an HPCO (High Pressure Cut Off) plumbed into the high side. This is a pressure switch that is normally closed, opens only if pressure gets up to ~ 430 PSI or so, to drop out the compressor in a fault situation (like very dirty/bent up condenser fins, engine fan failure, orifice tube plugged, extreme over-charge via Can-O-Death wally world "charge kit", etc.)

If you use a 1994 and on hose manifold assembly, it would have a HPCO mounting point to screw the HPCO into, it would have the safety pressure release (vents refrigerant to the atmosphere at >~500 PSI as a fail-safe to avoid something blowing up), and usually has the muffler on it too. These fit a particular compressor, don't know about your Sanden. The hose manifolds mount onto the compressor as a block (low and high ports on compressor), have a suction hose that would connect to the Accumulator/Driers output, have the high side hose that would go off to the condenser. Just need a liquid line from condenser output to orifice tube/evap.

Your setup would need to connect somehow the evap's output to the Accumulator/Drier's input, and keep it close and sturdy, as the A/D has a lot of mass, and it needs to sense evap output pressure (therefore temperature) to properly work the CPS. I think that connection may be the hardest part of the whole setup, just doing it and getting it sturdy. The A/D needs to be mounted vertical, as it has an internal baffle and drip hole that prevents any liquid refrigerant that may make it through the evap, from going on and slugging the compressor (bad).

 

Torky2, thanks very much. That provides a lot of clarity.

If I can find a way to use the '96 A/D and condenser it might make it possible to use stock '96 hose assemblies. I saw that Autozone listed a Orifice tube repair tube to attach at the evaporator inlet that mates to a Ford spring lock that may be usable. It's just over $10 so it won't break the bank to get one and try to fit it to the existing evaporator. I can also see the HCPO, low pressure cutoff switch, and other parts and switches you mentioned available.

I need to get a system diagram to see how they all go together, and I'll probably run out to Pull-a-part and see if I can grab a full hose assembly and associated switches and harnesses to see how I can put something together.

Your explanation was super helpful. Thanks again.

 

Hi,
I'm doing almost the same swap that you did.. I'm putting a '94 E150 5.8w w/carb into my '78 F100 with factory air..
Id love to see pics of your finished system and suggestions. My Compressor is the factory FS10. Im debating on
using the Vintage air manifold block, or get a hose set for a 95 F150 and just splice the old and new hoses.. Id also like to
change out the factory condenser with a newer type..
Thanks!