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Update: Enhanced A/C Performance
With The Smart VOV™
by I.M. Cool
Appeared July/October 1999 Cool Profit$ Magazine
© 2001 All Rights Reserved

Two Updates:
1. Question and Answer about the VOV.
2. Update from "Burb" owner

1. In June 1999, the following question was asked about the usage of the Smart VOV. We printed this question and our answer in the July/October 1999 edition of Cool Profit$ Magazine's Write Side Up (Letters To The Editor).

Will the VOV trigger the shutoff switch?

In your Dec. issue of Cool Profits you had an article about “Smart VOV.” I am confused as to how you can say this item is a direct replacement and no modifications are necessary when in your article you said the low side pressure was 20 psi, over I believe, 195. As any one in the field would know your low pressure switch on a CCOT system with R-12 should kick out at about 26-28 lbs (well above the 20 psi indicated in your article). If you could please shine some light on this subject I would be very grateful as I have not yet tried this product…but it sounds good working in Melbourne Florida. I understand the need for a few degree drop at the vent and I am sure that my customers would also be grateful. Thanks, Gary Akers, Master Tech, Pepboys, Melbourne, Florida. GAkers9940@aol.com.

CPM Answer:
I believe you may be referring to our March/April 1999 article titled Enhanced A/C Performance With The Smart VOV™. In that article, pressure readings for the original GMC Suburban R-134a system operating at 1500 RPM were 20-180 psi. For the system after the OE orifice tube was replaced by the VOV, those readings were 20-150 psi. And your concern is that how could the pressure get to 20 psi when the cutoff switch is normally set for 26-28 psi. In researching that I learned that there are two primary reasons for this apparent discrepancy. First, the pressure readings were probably not taken at the same location in the system where the cutoff switch is mounted. There could easily be a pressure difference between the two locations because of hose losses. Secondly, gauges are notorious for “tolerances;” it would not be difficult to get a reading that is 5 psi or more below actual system pressure.
Note also, that the readings are consistent between the OE and the modified system. Both show 20 psi as the lower limit. And the OE was taken before any modifications were done.

Here's an update on the continuing a/c performance of the modified Suburban from the truck's owner. It too appeared in the July/October 1999 edition of Cool Profit$ Magazine's Write Side Up (Letters To The Editor):

'95 Suburban Smart VOV update
Dear Cool Profit$ Magazine and readers,

This is an update on the GMC Suburban from Phoenix that had the Smart VOV installed in its air conditioning system last fall. Early in August we loaded up the (Typical) family in the Suburban and headed out for some shopping in and around the greater Phoenix metro area. Because it was expected to reach about 106°, and we were certain to be in stop-and-go traffic, I purposely tracked how the “Burb's” air conditioning system performed.

I kept the AC on normal cooling for the front, at low fan, and likewise for the back. The kids soon asked if they could control the AC in the back and when I asked why, thinking they wanted to turn the fan speed higher, I was surprised that they were both cold and wanted to turn it down lower, or off. Mrs. Typical then also commented that she was chilly up front. That really surprised me because in the summer she never complains about the cold, only being too warm. So, needless to say, I am convinced that the VOV has substantially improved the cooling capabilities of my Suburban.

In addition, the cool down time from the truck being in a sun-soaked mall parking lot was much faster than ever before. There are no exaggerations here, only the comments shared by my family on this and several other occasions, and my own personal experience. Thankfully, there are no more complaints about this car's AC not working. Karl “Typical,” Phoenix, AZ.

Back to the original article, click here.

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