[DeTomaso] A/C condensor fan test results

Sun May 5 21:50:10 EDT 2013

When I redid my AC system, I replaced the stock birdcage fan with a 3-way
motor. I estimate that the mid setting of the new fan was probably more
powerful than the high of the stock one, but the perception of airflow is
not scientific by any means. I would question if you could really tell if
the unit was iced over or not. Can you pull your front vents out and see
into your evaporator for evidence of ice?  That might be a better indicator.

Rob DuMoulin
904.476.8744
rob at dumoulins.net
www.kbsi.co
http://www.linkedin.com/pub/rob-dumoulin/0/1b6/58

On Sun, May 5, 2013 at 9:01 AM, Tom Shinrock <tmshinro at aol.com> wrote:

>
>  Scott,
>
> Thanks for your comments.   I don't think my evaporator is icing up
> because I never saw a reduction in air flow from the fan (which is what I
> assume you are referring to when you say "blower").  I find it hard to
> believe that the evaporator could ice up in the near 100 degree heat and
> ultra low humidity conditions in Phoenix.  I could only wish my system got
> that cold.  I will, however, do as you suggested the next time it stops
> working to see happens.  Just curious what is the solution to the
> evaporator icing up...dial in some heat from the heater?
>
> Thanks,
>
> Tom
>
>
>
>
>
>
>
> -----Original Message-----
> From: Scott Bell <scott at saccrestorations.net>
> To: 'Tom Shinrock' <tmshinro at aol.com>; detomaso <detomaso at poca.com>
> Sent: Sat, May 4, 2013 10:02 pm
> Subject: RE: [DeTomaso] A/C condensor fan test results
>
>
> Tom,
>
> Something else to consider... If the AC works for some period of time and
> then
> stops working, the problem could be the evaporator
> icing over. This is VERY common. To test, next time the AC stops working
> while
> driving, turn the AC compressor off with the
> thermostat knob. Leave if off for 5 minutes or so. During this time the
> blower
> should still be running. Then turn the AC compressor
> back on and see if the AC is again blowing cold. Also, when the evaporator
> is
> icing over, it is common to have a reduction in blower
> pressure. As the evaporator defrosts, the blower air pressure will
> increase.
>
> Also, the switch you added cuts the compressor off when the pressure gets
> too
> high or too low, as opposed to, too hot as you stated.
> If the compressor is turning off do to this switch, something is indeed not
> right. As you guessed, not enough air flow through the
> condenser on a hot day will cause the pressure to go to high and shutoff
> the
> compressor. This condition causes hoses to blow off on
> systems without a pressure switch.
>
> Scott
>
> -----Original Message-----
> From: detomaso-bounces at poca.com [mailto:detomaso-bounces at poca.com] On
> Behalf Of
> Tom Shinrock
> Sent: Saturday, May 04, 2013 7:38 PM
> To: detomaso at poca.com
> Subject: [DeTomaso] A/C condensor fan test results
>
> Those I met at the fun rally probably got bored/annoyed with my stories of
> my
> air conditioner not being effective on my drive from
> Iowa to Phoenix (believe me....I heard about it from Dena on the drive
> back).  I
> had the system filled will R-12 before I left Iowa.
> I put in a new rotary compressor and drier last summer along with a high
> temp
> cut off switch. Before that I never tried to get my
> A/C working.  I was pleased to find a number of people that claimed to have
> effective A/C with rear mounted condensers so I have
> hope that I can get mine to work.
>
>
> Gil Mares and Les Gray went out of their way to look at my system and put
> me in
> touch with some A/C experts in Phoenix.  To shorten
> a long story, when Les looked at the system we found that the A/C worked
> in the
> parking lot blowing 60 degree air with ambient temps
> around 100 in the car.   He didn't see any bubbles in the drier site
> glass.  He
> also noted that I had original hoses.  I called the
> experts that Gil had referred me to and gave them the results of the
> parking lot
> test.  Their opinion was that no bubbles indicated
> that the system was fully charged and the fact that  the A/C worked in the
> parking lot but not on the highway suggested that the
> condenser was not being taking enough heat out of the system which was
> probably
> due to a underpowered fan and/or an ineffective
> condenser.
>
>
> On the way home I would periodically turn on the air and find that it
> would blow
> cool air for a very short time and then stop
> working.  On my last day of driving I ran the A/C in the late morning
> before it
> got crazy hot and found that the air actually worked
> for about an hour and a half before it quit working.  During that stretch I
> heard a sound I've rarely heard; the A/C relay clicking
> on and off.  This experience pushed me further to the conclusion that my
> condenser wasn't pulling enough heat out of the system and
> when it got hot enough my cut off switch was shutting down the compressor.
>
>
> I replaced my stock condenser fan with a new fangled one last summer
> thinking it
> would be better.  Since then I've read many
> opinions that the stock fan moved more air.  John Buckman described to me
> how he
> tested various aftermarket fans using increasing
> amounts of cardboard at the condenser grill to determine which fan
> provided the
> most suction to hold the cardboard in place.  He
> said he did not conduct that test for the stock fan however.
>
>
> Feeling that my A/C would be more effective if I could move more air
> through the
> condenser, I decided to perform the cardboard test
> to see how my aftermarket fan compared to the stock fan.  Here's what I
> found:
>
>
>
> With my aftermarket fan installed I cut a piece of cardboard the size of
> the
> grill opening and turned the fan on via a battery
> charger and saw that the fan sucked the cardboard and held it to the
> grill.   I
> then taped more and more cardboard to this first
> piece of cardboard until the fan could no longer provide enough suction to
> hold
> the mass of cardboard against the grill.
>
>
> I then removed the aftermarket fan and re-installed my stock fan (by the
> way
> both fans had dense foam stuffed into the sides of the
> fan shroud to seal the gap between the shroud and car body to prevent the
> fan
> from sucking any air from inside the engine
> compartment).  I found the stock fan could easily hold the mass of
> cardboard I
> ended up with when testing the aftermarket fan.  I
> then proceeded to add more and more cardboard until the stock fan could not
> provide enough suction to hold the mass of cardboard to
> the grill.  Both tests were performed with the tub out.
>
>
> I don't have a scale small enough to weigh the different amounts of
> cardboard to
> quantify the difference in weight but I did
> calculate the equivalent area of card board that each fan could hold.  The
> aftermarket fan held 677 square inches of cardboard and
> the stock fan held 782 square inches (15.5% more).  So obviously I was not
> getting as much condenser cooling with the aftermarket
> fan.
>
>
> I then proceeded to test the A/C with the tub in.  I put a temperature
> probe in
> the dash vent which indicated 70 degrees ambient.  I
> turned the A/C on saw that the vent air temperature was an indicated 25
> degrees.
> I won't really know how good it performs until we
> get some hot weather around here.
>
>
>
> I heard a lot of people talk about parallel flow condensers.  I know I
> don't
> have a stock condenser but I don't really know what
> kind came with the car.   When I was switching condenser fans, I took a
> closer
> look at it and I'm wondering if it is a parallel flow
> design.   I took some pictures of it to see if someone can tell me what I
> have.
> http://poca.com/index.php/gallery/?g2_itemId=40199
>
>
> Any and all comments are welcome.
>
>
> Tom
> #5186
>
>
>
>
>
>
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