Bosshog454
Junior Member
- Joined
- Jun 23, 2019
- Posts
- 6
- Reaction score
- 23
- Location
- Arkansas
- First Name
- Branson
- Truck Year
- 1991
- Truck Model
- Suburban v2500
- Engine Size
- 350
Like most people I was not satisfied with the performance of my 1991 Suburban V2500 AC Performance. Most threads that I could find suggested replacing the compressor with a Sanden style unit, before spending the time and money I decided to look for improvements in the factory setup. I did this based on my experience with home HVAC unit and how frequently the underperformance is not because of the unit but rather the insulation of the home or duct work etc.
The good news: I was able to fix my AC for extremely cheap without buying any new components (although you will need a valve and some foam pipe isulation)
Tools / Equipment needed:
Step 1: install a valve on the inlet to the heater core, even if you aren't blowing air across the heater core that heat in your dash still gets crazy hot and contributes the heat in the cab. This made a noticeable difference in the AC temp but did not make it tolerable.
Step 2: separate the inlet and outlet lines to the rear ac. The inlet line comes out of the compressor and runs through the condensor in front of the grill. In the engine bay this line was around 140 degrees, this line then heads to the rear of the truck and into the rear ac unit. There is then an outlet line running out of the rear ac unit and back to the front of the truck and into the compressor. The problem is this, the hot inlet line from the compressor and the cool outlet line from the rear ac unit are strapped together for the entire length of the truck. The hot inlet line heats up the cool outlet line and by the time the outlet line reaches the front of the truck and runs back into the compressor it has gone from 100 degrees to about 138 degrees. So instead of putting cool refrigerant into the compressor and getting a temp increase from that point, you put hot refrigterant into it and get a temp increase from that hotter point. Here are the numbers according to my temp gun
Outlet line - as it spends more time strapped to that hot inlet line it slowly heats up
* rear of truck - 102 degrees
* under pass door - 108
* under fender corner - 118
* right before it meets the outlet line from the front unit - 138 degrees
I separated the two lines for the entire length of the truck and wrapped foam pipe insulation around the outlet line from the rear ac unit all the way back up to the engine bay so that it would not get heated up by the hot inlet line. I then secured both lines with separate brackets and screws. Now the outlet line is 108 degrees at the engine bay instead of 138. Step 1 and Step 2 made it to where my old suburban would keep me cool driving down the highway on a 100 degree arkansas day, the only problem now is when I'm going slow in town. So I moved on to step 3
Step 3: auxililiary fan on front condensor. I bought a 30 dollar 12v fan on amazon and installed it in front of the condensor on the radiator, I wired it to a 12v relay and then to the battery. I wired the relay to the AC compressor wires so that it turns the fan on whenever the ac compressor is engaged. With this addition my suburban is cool no matter what, if I'm parked completely still it starts to be less effective but in stop and go traffic I have zero problems and we just had one of the hottest weeks in Arkansas that I can remember. Every day was 100+ degrees with a heat index of like 114 at times. My temp gun said the concrete was about 125 degrees.
I know the Sanden compressor route is probably the most effective but I wanted to share this with anybody who is looking for a cheap and easy fix. If there is any reason that this setup is unsafe please let me know because this is my daily driver lol. My temp readings could of course be off a little bit because of the style gun I use but the undeniable fact is this, my suburban ac has been so bad that I didn't even use it during these hot months for the last several years, I just rowed my windows down. Now my AC is nice even during the hottest possible times.
The good news: I was able to fix my AC for extremely cheap without buying any new components (although you will need a valve and some foam pipe isulation)
Tools / Equipment needed:
Step 1: install a valve on the inlet to the heater core, even if you aren't blowing air across the heater core that heat in your dash still gets crazy hot and contributes the heat in the cab. This made a noticeable difference in the AC temp but did not make it tolerable.
Step 2: separate the inlet and outlet lines to the rear ac. The inlet line comes out of the compressor and runs through the condensor in front of the grill. In the engine bay this line was around 140 degrees, this line then heads to the rear of the truck and into the rear ac unit. There is then an outlet line running out of the rear ac unit and back to the front of the truck and into the compressor. The problem is this, the hot inlet line from the compressor and the cool outlet line from the rear ac unit are strapped together for the entire length of the truck. The hot inlet line heats up the cool outlet line and by the time the outlet line reaches the front of the truck and runs back into the compressor it has gone from 100 degrees to about 138 degrees. So instead of putting cool refrigerant into the compressor and getting a temp increase from that point, you put hot refrigterant into it and get a temp increase from that hotter point. Here are the numbers according to my temp gun
Outlet line - as it spends more time strapped to that hot inlet line it slowly heats up
* rear of truck - 102 degrees
* under pass door - 108
* under fender corner - 118
* right before it meets the outlet line from the front unit - 138 degrees
I separated the two lines for the entire length of the truck and wrapped foam pipe insulation around the outlet line from the rear ac unit all the way back up to the engine bay so that it would not get heated up by the hot inlet line. I then secured both lines with separate brackets and screws. Now the outlet line is 108 degrees at the engine bay instead of 138. Step 1 and Step 2 made it to where my old suburban would keep me cool driving down the highway on a 100 degree arkansas day, the only problem now is when I'm going slow in town. So I moved on to step 3
Step 3: auxililiary fan on front condensor. I bought a 30 dollar 12v fan on amazon and installed it in front of the condensor on the radiator, I wired it to a 12v relay and then to the battery. I wired the relay to the AC compressor wires so that it turns the fan on whenever the ac compressor is engaged. With this addition my suburban is cool no matter what, if I'm parked completely still it starts to be less effective but in stop and go traffic I have zero problems and we just had one of the hottest weeks in Arkansas that I can remember. Every day was 100+ degrees with a heat index of like 114 at times. My temp gun said the concrete was about 125 degrees.
I know the Sanden compressor route is probably the most effective but I wanted to share this with anybody who is looking for a cheap and easy fix. If there is any reason that this setup is unsafe please let me know because this is my daily driver lol. My temp readings could of course be off a little bit because of the style gun I use but the undeniable fact is this, my suburban ac has been so bad that I didn't even use it during these hot months for the last several years, I just rowed my windows down. Now my AC is nice even during the hottest possible times.
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