SPF Air Conditioning

[Dave Hood]

Over the 13 years I've owned my SPF MKI, it's been a constant challenge to keep my AC running well. I've installed Rick Muck's air sealing kit and relay upgrade and have had the AC checked and serviced about every two years. I live in the Charlotte area and it's a challenge to drive the car without functioning AC for at least six months of the year. I'm just curious if anyone has an SPF car where the AC has worked consistently for a number of years. Or, has anyone replaced the SPF AC system with another solution?

 

[Mike Christian]

I can't speak directly about the SPF AC system just yet, but I recently created a custom system for an older 911 I have. In doing so, I used:

two newer more efficient condensers
a newer more efficient evaporator,
an electric compressor with ECU management,
better flowing fans
more cockpit vents

All of this allowed me to house the system in the front half of the car and reduce hose lengths and reduce total system weight.

The 911 is a targa with lots of glass and a black interior. It is based in SoCal, so there is plenty of heat soaking. This system delivers temps in the 30s after a few minutes.

I recently did cooling system work on my GT40 and had the seats and bulkhead panels out. While running the engine and looking for leaks, the amount of heat coming through the bulkhead was much much more than I expected.

My initial reaction to your question is to consider:

first minimizing the heat coming in from the engine area by insulating the bulkhead as best you can. Also, will a glass back window help? I have one and will be installing it soon.

see if there is a way to measure the heat coming through the tunnel area, and insulate it if possible.

consider adding more system vents.

I am not familiar with the evaporator location and setup (yet), but I would look to see if it can be better insulated and if the fan needs to be (or can be) improved.

If those don't make much of an improvement, then I think you would start looking at the major components for consideration.

Just a thought...

 

[Jim Craik]

I just spent a few hours with Lance down at Hillbank, he showed me around his SPF GT40… told me a secret, if you block off the heater hose in the nose you’ll gain more cooling. We are in CA so heat is never required. Apparently the heat valve doesn’t always close all the way and the heater core shares the space with the ac core…

I had noted the ac loosing cooling towards the end of a long drive. Anyway I blocked it off and I’m testing it right now. I blocked mine off but it would be easy to install a valve for those in cold weather.

 

[Dave Hood]

I can't speak directly about the SPF AC system just yet, but I recently created a custom system for an older 911 I have. In doing so, I used:

two newer more efficient condensers
a newer more efficient evaporator,
an electric compressor with ECU management,
better flowing fans
more cockpit vents

All of this allowed me to house the system in the front half of the car and reduce hose lengths and reduce total system weight.

The 911 is a targa with lots of glass and a black interior. It is based in SoCal, so there is plenty of heat soaking. This system delivers temps in the 30s after a few minutes.

I recently did cooling system work on my GT40 and had the seats and bulkhead panels out. While running the engine and looking for leaks, the amount of heat coming through the bulkhead was much much more than I expected.

My initial reaction to your question is to consider:

first minimizing the heat coming in from the engine area by insulating the bulkhead as best you can. Also, will a glass back window help? I have one and will be installing it soon.

see if there is a way to measure the heat coming through the tunnel area, and insulate it if possible.

consider adding more system vents.

I am not familiar with the evaporator location and setup (yet), but I would look to see if it can be better insulated and if the fan needs to be (or can be) improved.

If those don't make much of an improvement, then I think you would start looking at the major components for consideration.

Just a thought...

Thanks, Mike. My main concern is the temperature of the air coming out of the AC vents. Fully charged, the system is blowing air around 58 degrees. That's almost 10 degrees warmer than a modern AC system should be producing when the outside air temp is around 90 degrees. Even with a well functioning system, a GT40 in the Southeastern states during the Summer is a challenge.

 

[Dave Hood]

I just spent a few hours with Lance down at Hillbank, he showed me around his SPF GT40… told me a secret, if you block off the heater hose in the nose you’ll gain more cooling. We are in CA so heat is never required. Apparently the heat valve doesn’t always close all the way and the heater core shares the space with the ac core…

I had noted the ac loosing cooling towards the end of a long drive. Anyway I blocked it off and I’m testing it right now.

Thanks, Jim. I blocked off my heater hose several years ago. I'm sure that helped a bit.

 

[DaveM]

Thanks, Mike. My main concern is the temperature of the air coming out of the AC vents. Fully charged, the system is blowing air around 58 degrees. That's almost 10 degrees warmer than a modern AC system should be producing when the outside air temp is around 90 degrees. Even with a well functioning system, a GT40 in the Southeastern states during the Summer is a challenge.

Something not right there Dave. I get vent temperatures in the mid 40's with ambient 90 degrees. Are you sure no leaks? In 17 years of ownership I've replaced the evaporator twice due to pinhole leaks from corrosion. I'm not sure if corrosion is due to evaporator box being very contained or just internal due to acids in the refrigerant. I would be very interested to know of an alternative evaporator.

 

[Dave Hood]

Something not right there Dave. I get vent temperatures in the mid 40's with ambient 90 degrees. Are you sure no leaks? In 17 years of ownership I've replaced the evaporator twice due to pinhole leaks from corrosion. I'm not sure if corrosion is due to evaporator box being very contained or just internal due to acids in the refrigerant. I would be very interested to know of an alternative evaporator.

Thanks, Dave. I had my mechanic put dye into the system yesterday and we'll look for leaks. That's next on my list.

 

[DaveM]

Thanks, Dave. I had my mechanic put dye into the system yesterday and we'll look for leaks. That's next on my list.

Dye may not detect pinhole leaks in the evaporator since it's buried in the box. I had best luck with a halogen gas sniffer.

 

[Dave Hood]

Dye may not detect pinhole leaks in the evaporator since it's buried in the box. I had best luck with a halogen gas sniffer.

Thanks, Dave. I appreciate that input.

 

[Mike Christian]

I am certainly no expert, but after checking proper charge and if you find no leaks, I would just check hose temps between major components to try to narrow down where the issue might be.

The line from compressor to condenser should be hot. From there through the dryer to the expansion valve it should be warm. Leaving the expansion valve into the evaporator it should be real cold and leaving the evaporator to the compressor it should be cool. This should be relatively easy to check.

Then my interest would switch to the Evaporator area. Anything blocking good airflow through it prevents it operating as it should. Check that condensation is draining out and not freezing, and that the evaporator box is well sealed (consider insulating it).

This all assumes that the system is properly designed to begin with. I have had my SPF for some 18 years, but, honestly, I couldn't tell you if it ever performed well given that I never use it.

After getting the car running again, I am adding AC to my list as a system to check out as 18 years is too long without being serviced. Thanks for the reminder and please post your progress...I could be following in your footsteps!

 

[Dave Hood]

I am certainly no expert, but after checking proper charge and if you find no leaks, I would just check hose temps between major components to try to narrow down where the issue might be.

The line from compressor to condenser should be hot. From there through the dryer to the expansion valve it should be warm. Leaving the expansion valve into the evaporator it should be real cold and leaving the evaporator to the compressor it should be cool. This should be relatively easy to check.

Then my interest would switch to the Evaporator area. Anything blocking good airflow through it prevents it operating as it should. Check that condensation is draining out and not freezing, and that the evaporator box is well sealed (consider insulating it).

This all assumes that the system is properly designed to begin with. I have had my SPF for some 18 years, but, honestly, I couldn't tell you if it ever performed well given that I never use it.

After getting the car running again, I am adding AC to my list as a system to check out as 18 years is too long without being serviced. Thanks for the reminder and please post your progress...I could be following in your footsteps!

Thanks, Mike. Great suggestions.

 

[Rick Muck- Mark IV]

A positive "on/off" valve for the heater line is a good move, keeping any warm/hot water out of the heater-A/C box is a benefit.

Ensure your flex tubes under the dash are not crushed or restricted; some early GTs had them damaged often.

Opening the intake vents on either side of the front nose will help with mixing ambient air with the hot air coming off the radiator. The openings are intended to feed the brake ducts, but the nose fiberglass is not cut open, so no air moves into the nose. You can reach in and trace the shape with a pencil, remover the front clip and cut the openings. You can finish the openings with some self-adhesive vinyl door edge molding material. This will add more ambient air to reduce the temperature in the nose reducing the workload on the A/C and reducing the heat of any air intrusion.

Just as important is preventing ambient/hot air intrusion into the cockpit. The A/C will be much more effective if it doesn't have to work as hard against the entire Earth's atmosphere! Some sealing improvements are here: https://www.gt40s.com/threads/spf-gt-water-air-sealing-the-diy-thread.29631/

 

[Ian Anderson]

How humid are you driving in?
The under dash units have been known to freeze / ice up
Once this happens no airflow through the unit so no cooling.

Ian

 

[Dave Hood]

How humid are you driving in?
The under dash units have been known to freeze / ice up
Once this happens no airflow through the unit so no cooling.

Ian

Charlotte is very humid, which works against any AC system for sure.

 

[Dave Hinze]

I bought SPF MK2 P2125 (circa 2008) about 2 yrs ago and live in Chandler, AZ where it gets quite hot. I believe my car has had the suggested improvements done by the previous owners. For what it’s worth, I had a sticky expansion valve that was short cycling the compressor on/off every few minutes which was affecting the air temperature. After that was replaced, it improved. Even though the air temp coming out or the vents is adequate, I find the blower fan to be underpowered in the SPF. I also have a CAV MK1 and the AC cools much better and the fan blows harder.

 

[Tim Terry]

Hello, Dave. Can you provide a reference to the expansion valve? Thanks!