I recently decided to do something about the very poor performance of my=20
dash air system. After reviewing a plethora of GMC-Net messages and a=20
number of web sites I decided that the real problem is not cooling capacity=
=20
but lack of airflow on the evaporator side of the system. My solution was=20
to add a couple of additional air ducts to the passenger compartment, one=20
on the drivers side (in the floor just above and to the left of the brake=20
peddle) and the other on the passenger side (just below the glove box).
Someone had suggested using industrial vacuum cleaner blast gates and 3"=20
hose to install fresh air vents. I thought that would also work well for my=
=20
air conditioner upgrade. I ordered the hose (DF100), 2 blast gates (DF121)=
=20
and 4 clamps (DF117) from Trendlines (woodworking tool supply company,=20
800-767-9999).
The blast gates are a 2 piece aluminum affair with a moveable steel plate=20
that acts as a cutoff valve. I unscrewed the two halves of each blast gate=
=20
and discarded the steel plates. I cut off the excess aluminum so that all I=
=20
had left was 4 square flanges. Each flange has four mounting holes and a 3"=
=20
hose port.
I removed the coolant tank and the washer fluid tank from the front of the=
=20
HVAC box. I remounted the coolant tank to the fire wall on the far right=20
(above the engine battery). I am planning on replacing the washer tank with=
=20
a smaller one and mount it to the far left fire wall. I may replace it with=
=20
a 12v solenoid valve connected to the house water system. I rarely use the=
=20
windshield washer so I have not decided yet.
I used a 2 7/8" hole saw with an extension to make 2 holes in the front of=
=20
the HVAC box and two holes in the floor. I used the flanges (made from the=
=20
blast gates) as templates to drill mounting holes for each flange. After=20
attaching all four flanges I cut, routed, and clamped two pieces of 3"=20
hose to connect the flanges on the HVAC box to the flanges in the floor.
I needed a way to control the quantity and direction of airflow so I looked=
=20
at various grills and vents. I decided to use a plastic "eyeball" style air=
=20
vent typically used in aircraft. I found one (part number 13-03800) sold by=
=20
Aircraft Spruce and Specialty (800-831-2949). This vent will allow you to=20
adjust the airflow and direction for each air outlet. I mounted the air=20
vents with Velcro so they can easily be removed if I need full airflow (in=
=20
the event of a roof air failure).
I also moved the power source for the HVAC blower's high speed circuit=20
breaker from the battery circuit to the alternator circuit (center post of=
=20
the battery isolator). This reduces the load on the battery isolator and=20
gives the blower motor an extra 1.5 volts or so. Some of the increased=20
voltage is from bypassing the diode drop in the battery isolator and some=20
is from bypassing voltage drops in the wiring harness.
This upgrade directs cool air from the cool side of the evaporator coil=20
directly to the passenger compartment. IT WORKS EXCEPTIONALLY WELL
I=20
don't need to run the roof air until the outside temps reach the upper=20
80's. I don't need to run the dash air blower on high until the outside=20
temp gets above the mid 80's. Before this upgrade I was running the roof=20
air anytime the outside temps got above the lower 70's.
This upgrade was cheap, reasonably easy to install and should save quite a=
=20
bit of this $2+/gal gas we have been seeing here in Michigan this summer.=20
It will also reduce the wear and tear on my new Genrac and give me a way to=
=20
get home in a reasonably comfortable manor if the roof air fails again.
The only downside I see to this upgrade is that it only works for the A/C.=
=20
During the heating season I will have to close off my new vents and suffer=
=20
with the original poor heating system. Fortunately I do most of my travel=20
during the warmer months so it should not be a problem.
Dave
Ann Arbor, MI.
73 Sequoia (26'/455/HEI/TBI/160=B0/3.42/Q55G)
dash air system. After reviewing a plethora of GMC-Net messages and a=20
number of web sites I decided that the real problem is not cooling capacity=
=20
but lack of airflow on the evaporator side of the system. My solution was=20
to add a couple of additional air ducts to the passenger compartment, one=20
on the drivers side (in the floor just above and to the left of the brake=20
peddle) and the other on the passenger side (just below the glove box).
Someone had suggested using industrial vacuum cleaner blast gates and 3"=20
hose to install fresh air vents. I thought that would also work well for my=
=20
air conditioner upgrade. I ordered the hose (DF100), 2 blast gates (DF121)=
=20
and 4 clamps (DF117) from Trendlines (woodworking tool supply company,=20
800-767-9999).
The blast gates are a 2 piece aluminum affair with a moveable steel plate=20
that acts as a cutoff valve. I unscrewed the two halves of each blast gate=
=20
and discarded the steel plates. I cut off the excess aluminum so that all I=
=20
had left was 4 square flanges. Each flange has four mounting holes and a 3"=
=20
hose port.
I removed the coolant tank and the washer fluid tank from the front of the=
=20
HVAC box. I remounted the coolant tank to the fire wall on the far right=20
(above the engine battery). I am planning on replacing the washer tank with=
=20
a smaller one and mount it to the far left fire wall. I may replace it with=
=20
a 12v solenoid valve connected to the house water system. I rarely use the=
=20
windshield washer so I have not decided yet.
I used a 2 7/8" hole saw with an extension to make 2 holes in the front of=
=20
the HVAC box and two holes in the floor. I used the flanges (made from the=
=20
blast gates) as templates to drill mounting holes for each flange. After=20
attaching all four flanges I cut, routed, and clamped two pieces of 3"=20
hose to connect the flanges on the HVAC box to the flanges in the floor.
I needed a way to control the quantity and direction of airflow so I looked=
=20
at various grills and vents. I decided to use a plastic "eyeball" style air=
=20
vent typically used in aircraft. I found one (part number 13-03800) sold by=
=20
Aircraft Spruce and Specialty (800-831-2949). This vent will allow you to=20
adjust the airflow and direction for each air outlet. I mounted the air=20
vents with Velcro so they can easily be removed if I need full airflow (in=
=20
the event of a roof air failure).
I also moved the power source for the HVAC blower's high speed circuit=20
breaker from the battery circuit to the alternator circuit (center post of=
=20
the battery isolator). This reduces the load on the battery isolator and=20
gives the blower motor an extra 1.5 volts or so. Some of the increased=20
voltage is from bypassing the diode drop in the battery isolator and some=20
is from bypassing voltage drops in the wiring harness.
This upgrade directs cool air from the cool side of the evaporator coil=20
directly to the passenger compartment. IT WORKS EXCEPTIONALLY WELL
I=20don't need to run the roof air until the outside temps reach the upper=20
80's. I don't need to run the dash air blower on high until the outside=20
temp gets above the mid 80's. Before this upgrade I was running the roof=20
air anytime the outside temps got above the lower 70's.
This upgrade was cheap, reasonably easy to install and should save quite a=
=20
bit of this $2+/gal gas we have been seeing here in Michigan this summer.=20
It will also reduce the wear and tear on my new Genrac and give me a way to=
=20
get home in a reasonably comfortable manor if the roof air fails again.
The only downside I see to this upgrade is that it only works for the A/C.=
=20
During the heating season I will have to close off my new vents and suffer=
=20
with the original poor heating system. Fortunately I do most of my travel=20
during the warmer months so it should not be a problem.
Dave
Ann Arbor, MI.
73 Sequoia (26'/455/HEI/TBI/160=B0/3.42/Q55G)
