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A while back, I saw a write up on improving the stock HVAC box.  Essentially, it consisted of adding a wedge shaped plenum between the fan and the box, to expose more of the evaporator core to the air flow, along with some other improvements.  Trouble is, I can't remember where I read it; here, in the poca newsletter, or elsewhere.  Can anyone point me in the right direction?  TIA, Rodney

Last edited by ufo-low
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You are looking for the article written by former POCA President Gerry Romack, member of the Great Lakes Pantera chapter-

I looked into this a year or so ago. Gerry used a 3-speed aftermarket blower assembly that I had trouble finding at a reasonable price. The only source I found, by matching photographs, was from Australia and it was stupid expensive. There are many universal blower assemblies that look much like the one Gerry used but the space available is very limited and I’m not sure an alternate unit could be used as a substitute.

for some reason I am unable to post a link to the article, but if you do a Google search for Great Lakes Pantera club you will get to their homepage, search on the left-hand side for technical articles


Great - thanks for the tip.  I found a similar blower assembly on e-bay from an outfit called Mobile Climate Controls - think I paid under $100 for it.  Nothing really wrong with the original except it is about 5 pieces and hard to arrange properly in anything but the stock box.  The MCC unit is all one assembly so much easier to work with.

Just on improvements - and this may be an extremely dumb question - if you replaced the compressor with a R 134a compatible rotary , could you still run the system on R 12 A  refrigerant and not replace the expansion valve in the air box ???

The R 134a compatible rotary has a higher rated pressure but the rest of the system would remain exactly the same - unchanged and in fact the system pressures , with R 12 a in it would be unchanged ??

I am now waiting for the slings and arrows of experience  to arrive ...!!!

The question would be why do think this is of benefit?

The R134a compressor has a higher rated pressure rating because an R134a system operates at a higher pressure, the reason why you have to change the expansion valve (orifice size). You are going to over pressure the system or have a lot less R12 in it and reduced cooling. Why not just get a rotary compressor rated for R12?

I tried but could only buy the get the 134a rotary compressor and reasoned that if I wanted to upgrade the compressor in future the increased Max pressure rating would be still good for 134a refrigerant upgrade . 

Also just trying to get out of pulling the expansion valve ! Also have a bottle of R12a that I would like to reuse for the recharge .

I would have thought the refrigerant type itself , volume of refrigerant in the system combined with the expansion valve orifice effectively sets the maximum circulation pressure of the system and if the compressor is rated for a higher maximum pressure all well and good. The system should stabilize  at the pressure drop set by the TX valve and the refrigerant vapor pressure  and fill . If the compressor was pushing more R 12 a refrigerant around  it would just be a bit colder in the cab .

It appears the seals and lubricant in the compressor  would still be compatible with the R12a as this is less aggressive than the R134a.

If not sounds like the dash may have to come out again ........!!!

The PAG oil in new compressors is NOT compatible with the mineral oil, you will need to drain and flush the new compressor and existing lines thoroughly and use an ester oil to prevent gumming up the system. The dash does not need to come out to switch the expansion valve it is accessible from the passenger foot well.


When  I was dealing with my AC system two years ago, I got a 134 compressor from Sanden and was told just to flush/change the oil to run R12.  NO difference to compressors......   I think I also bought the larger compressor.....7 series?  It's something like 2 cubic inches larger in capacity or some number like that....... forget the exact spec.....which changed.

Also, replace the blower fan with a commonly available 3 speed motor....wire up only two of the speeds....per taste/needs. No need to get too complicated. Use relays or fan controller kit...... to preserve fan switch.

If you may need to get new hose ends to attach to Sanden properly.  Also, if you cannot get charge ports on the compressor, you will need them on the hoses somewhere............   There are 90 degree crimp fittings that have the threaded ports on them to help out.....   The stock Ford "closeable" fittings will no longer work....sell them to a Mustang fanatic!


Thanks Steve.

Great information and encouraging .

I brought the SD7H15 Sanden which is quite probably the slightly larger unit you purchased. Was going to flush it with the r12 mineral oil and reuse R12. I did buy the new three speed fan unit from Halls but when I went to put the dash in it was simply easier to drop the old fan unit back in . The wiring threw me because I did not get it was a three speed not a two speed. Those crazy Mexicans ! Also the cable vent controls looked like they needed some work to fit them .  Another future rainy weekend job I think !

The hose ends are slightly short to the compressor ( boy -what fun it was getting them back  through the side channel ) and the fit under the dash is something else , as 6997 is a factory RHD.

The hoses and pedals are in a long term ,permanent and intimate relationship.

The charge ports will have to be installed on the hoses. so that will be a good way to close the gap to the compressor .

Both the original York compressor , fittings and all associated hardware are FUBAR big time ! ( 30 years in a slightly moist box can do that to you...!) . Even a mustang guy wouldn't want them unless he has a boat.

The rear fan unit looks OK , new dryer unit is ready to go . Getting closer !

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