Automotive Air Conditioning Information Forum

I have a 1977 Ford F250 with a Cummins Diesel swap. It is a factory AC truck. When I did the swap, I flushed out the factory evaporator several times, bought a new Sanden SD7H15 compressor, expansion valve, and largest parallel flow condenser I could fit in the front of the truck. I also put a new fan in and foam on the damper doors. It's got the stock mechanical fan on the engine. The system was vacuumed down and charged. The AC blows cold-ish, 50* or so on a hot day. I've had a few 1997 F250s that would freeze you out of the cab in the middle of a warm 95* summer day in Florida.

What can I do to get it to blow colder? Any recommendations?

Thanks,
Tobin

I have a few questions to begin the discussion. Did you charge it by weight or pressure? What oil did you put in it and how much? What pressures are you currently seeing at ~1,800 RPM?

We charged it by pressure if I remember correctly.

I believe the compressor came pre-charged with oil, but I did buy Sanden SP-15/PAG oil for it, so if we had to use oil that is what we used.

I will have to check the pressures and get back with that info.

My sources don't list the refrigerant/oil specs for your original R-12 truck. Is there an A/C decal someplace? It's usually located on the radiator support or underside of the hood. If so, please post what it says.

Another question. I noticed that you didn't mention the dryer. Did you change that out as well with one having R-134a-compatible desiccant?

The only thing factory is the evaporator, which was thoroughly flushed out multiple times with commercial solvent and pressurized flush system.

I don't have the factory oil specs, as it was R12 so I didn't look into that.

Yes, brand new universal R-134a drier was placed in the system.

Here is a quick run down of what was used:
Evaporator - Original 1977 Ford F-Series (or original looking) that was flushed and cleaned out
Condenser - Universal parallel flow, I need to look for the size but something like this https://nostalgicac.com/14-x-18-superfl ... enser.html
Compressor - Sanden S6H15 brand new (Sanden, not knock off)
Expansion Valve - Brand new universal (connects directly to high/low side of evaporator)
Drier - Universal https://nostalgicac.com/driers-valves/b ... r-943.html
Lines - Custom made rubber lines by local shop
Refrigerant - R134a (charged by pressure IIRC)
Oil - PAG oil

What suggestions has your parts supplier mentioned. As to not go over things already discussed?

Tim wrote:What suggestions has your parts supplier mentioned. As to not go over things already discussed?

I haven't talked to anyone about it except on this forum.

It's relatively cold here so I am waiting for it to warm up some to get some pressures and temperatures.

It does put off a lot of condensation. I sometimes wonder if the evaporator freezes up.

I do need a fan shroud, but that shouldn't make a difference at highway speed.

Verify the compressor RPM.

With the diesel engine's narrow operating range, swapping engines & compressors can lead to a mismatch. A compressor that is too small or spinning too slowly will give poor cooling.

The OEM compressor for your truck was a 210 cc/rev York type compressor. If you install a 148 cc/rev compressor, and underdrive it - you get poor cooling.

bohica2xo wrote:Verify the compressor RPM.

With the diesel engine's narrow operating range, swapping engines & compressors can lead to a mismatch. A compressor that is too small or spinning too slowly will give poor cooling.

The OEM compressor for your truck was a 210 cc/rev York type compressor. If you install a 148 cc/rev compressor, and underdrive it - you get poor cooling.

The Sanden SD7H15 is what came on the Cummins for a 1997 Ram pickup but definitely could be undersized for the Ford Evaporator. I will get a tach on this thing and see if I can get RPM or measure and figure out the pulley ratio. I did some looking and I think the mounting style is somewhat universal so should I be looking at a larger compressor? What would a compressor with too much displacement do to the system?