Greetings from Florida,

I am new to these forums and I am here to learn how best to improve the Automotive HVAC system in my Hummer H1. I am learning and I am not afraid to do research and become educated, but I have very little experience with HVAC in general.

H1's produced up until 1997.5 had an electro servo motor flap operating system. In 1998, a newer system was installed that was vacuum controlled.
The early system performs very poorly in hot climates. It is very common for pre-1997.5 H1's to be upgraded to the 1998-2004 cooling system, at a cost of $3,000 USD and 3 days worth of labour. This involves substantial cost and down time for the vehicle and a lot of cutting and modifying of vehicle components to alter the electro servo motor system to the vacuum system.

I have a limited edition truck and I want colder A/C, but I do not want to deal with "hacking up" a limited edition truck to install the upgraded HVAC system.

So far, I have done the following:

1. Bypassed heater core (No more heater or hot water mixing)
2. Charged system fully (R134A) and added Ice32
3. Added extra cold air ducts and hoodscoop in front of vehicle to increase air flow (Factory OEM upgrades)
4. Had truck taken to several different Automotive HVAC technicians that I did due-diligence on, that are experienced.

I noticed that the HVAC temperature was always "comfortable" when it was raining outside, or when I was driving durning evening hours with no sun...but during the heat of the day, it does not cool worth a darn.

One of the techs looked at the condenser and poured water over the condenser while reading the R134A gauges. There was a significant drop in temperature on the R134A gauges. He has recommended a new condenser with parallel flow coils and adding a cooling fan on top of the condenser, because a fan is not installed on H1's condensers from the factory, but an aftermarket SPAL unit is available.

I also looked at the dryer and noted that on the later Hummer H1's, the increased the size of the filter/dryer assembly. I did some research and found a filter/dryer that will fit in the stock mounting location, that will give me double the internal volume compared to the factory OEM filter/dryer. I have read that increasing the internal volume of the filter/dryer will give the freon more room to expand, therefore, making the air cooler.

A friend of mine is a retired Airconditioning man of 40 years experience and former automobile technician. On his Ford Retractable with Factory A/C, he retrofitted the aftermarket system from R134A to R12. He is a die-hard R12 fan and says that the vent temperatures were 8-10 degrees cooler with R12 versus the R134A. He offered to convert my H1 in an EPA certified facility.

So here are the questions:

1. Based on the test of pouring water over condenser and seeing significant drops in temperatures, a new, high efficiency condenser should help, along with a "pusher" fan mounted on top, correct?
2. By using a larger filter/dryer with double the internal volume of the factory filter/dryer, do you expect that this will help with achieving lower A/C temps?
3. Cost no object on refrigerant- Should I flush the system for 10 hours and attempt a R134A to R12 conversion??? I know I need to remove the compressor and drain the oil and make sure that the system has been flushed very well due to oil compatability. I looked at the new parallel flow condenser and the filter/dryer and *both* are rated for R12 and R134A.
4. Can I get cooler temperatures with George Goble's refrigerants- ie. CoolTop/Autofrost/R406?

Thanks for your time. I am learning here. I would love to have ice cold A/C!

For those that are interested, here is an overview of the H1 Cooling System:

Here are the upgraded cooling system components- Parallel Flow Condenser with SPAL Condenser Cooling Fan, and larger filter/dryer. This is an OEM kit that the dealer sells:

Open to any and all ideas/suggestions. Thanks again.