The Shop Truck

[K85 Octane]

On my ‘68 w/5.3 it stayed at the factory temperature without a problem. Wasn’t happy about 210 but that’s what factory was. I ran a Spectre replacement rad and Windstar fans. Looked clean and worked great, AC, idle, or hot freeway.

For the AC, I don’t know what unit you used but if it’s under dash aftermarket, have you set the coil temperature screw in the unit? (I don’t know what it’s called. I had to adjust it some to get the compressor happy and vent degrees to come down)

 

[r3dd0g]

Good call on sealing the airflow into the radiator. The filler panels look nice. I would add some filler foam or rubber sheets to make sure all the air coming into the grill has to go through the radiator. If the still doesn't do the trick, you might need some hood vents like on your Duramax.

Something may have already been purchased.

Need a filler for dad's Ranchero gonna look and see.

Where did you have the sensing bulb for the thermal expansion valve

In the last picture I posted you can see the thermal expansion valve and the coil (not bulb) clipped to the top of the return line coming out of the firewall. That's where the Old Air instructions said to put it. The issue is when I wrap it with the insulation and rev the engine, the low side pressure drops into the low 20's (at 85F ambient) and the high side goes up into the 300s until it trips the overpressure switch and shuts the compressor off, then it just cycles the compressor on and off real quick and stalls the truck if I'm idling. I got the A/C working fairly good (55F out the vents) by pulling 10oz of refrigerant out and removing the insulation from the expansion valve coil. Now the low side sits in the 25-30psi range (should be around 45) and the high side cycles with the fan. The trinary switch will kick the fans on at 245psi which causes pressure to drop down to 185psi where they kick back off and the cycle repeats.
The only issue I have now is that when the engine compartment heat soaks after driving, it takes quite a while of driving (no stopping) before the A/C gets down into the low 60s and never gets down to 55 like it will when everything is cooled down. Hood vents may help with this as well.

On my ‘68 w/5.3 it stayed at the factory temperature without a problem. Wasn’t happy about 210 but that’s what factory was. I ran a Spectre replacement rad and Windstar fans. Looked clean and worked great, AC, idle, or hot freeway.

For the AC, I don’t know what unit you used but if it’s under dash aftermarket, have you set the coil temperature screw in the unit? (I don’t know what it’s called. I had to adjust it some to get the compressor happy and vent degrees to come down)

My truck stays in the 210-220 range when I'm on the freeway at 70-80. The fans shouldn't be running while on the freeway, but they are so something isn't right. Stop and go/idle/45mph it will stay closer to the 200F temp where the fans kick on.

I'm not sure what the coil temperature screw you're talking about is.

 

[Wes Harden]

Sounds to me like the evaporator is freezing.
Still a little fuzzy on capillary tub placement.
Old Air wants it on the engine side of the firewall?
Place the tube higher than the valve on the out let(suction) side, with a loop that is above the highest part of evaporator.
Maybe some foil tape to insulate till the bugs are worked out.

 

[r3dd0g]

Sounds to me like the evaporator is freezing.
Still a little fuzzy on capillary tub placement.
Old Air wants it on the engine side of the firewall?
Place the tube higher than the valve on the out let(suction) side, with a loop that is above the highest part of evaporator.
Maybe some foil tape to insulate till the bugs are worked out.

You should be able to see it better in that picture, although the coil is insulated in this picture. Yes it's on the engine side of the firewall. The suction side of the evaporator is the top tube where the coil from the capillary tube is clipped, the expansion valve is below the suction tube connected to the other side of the evaporator.
Why does the capillary tube need to loop above the evaporator? That's a completely sealed system separate from the evaporator.

 

[Wes Harden]

Maybe an old wives tale, especially since modern tev incorporate the capillary integral.

 

[imiceman44]

You should be able to see it better in that picture, although the coil is insulated in this picture. Yes it's on the engine side of the firewall. The suction side of the evaporator is the top tube where the coil from the capillary tube is clipped, the expansion valve is below the suction tube connected to the other side of the evaporator.
Why does the capillary tube need to loop above the evaporator? That's a completely sealed system separate from the evaporator.

The loop creates a static pump effect.
They do the same with solar heat.
At least that is how I understood it

 

[r3dd0g]

That makes sense, but it would be such a small pressure differential that I can't imagine it would make a difference.

 

[K85 Octane]

You have the black goop around the line right?
It’s a screw on the side of the box, evaporator I think. It adjusts the temperature the thing is allowed to get to and by adjusting, it also changes how long the pump runs.

Could it also be getting warm because your air intake temps? I see a filter sitting right on the TB…behind the radiator. Dunno. Just spitballing.

 

[Chevy305]

Did you purge the system before filling? It's possible you may have moisture in it.

 

[r3dd0g]

You have the black goop around the line right?
It’s a screw on the side of the box, evaporator I think. It adjusts the temperature the thing is allowed to get to and by adjusting, it also changes how long the pump runs.

Could it also be getting warm because your air intake temps? I see a filter sitting right on the TB…behind the radiator. Dunno. Just spitballing.

No black goop, that's the insulation I said I took off to make it work better. When the pigtail is insulated my low side pressures drop down into the teens. I don't think the problem can be solved by cycling the compressor more so I'm not going to mess with the thermostat, I believe that is just to prevent freezing in the coils which isn't a problem currently. All of the issues I have happen right when you first start the truck and turn on the A/C, no time for things to freeze up.

I know I have the typical "hot air" intake going on, it certainly is adding to the heat problems, but I don't think that's the main source. Once I turbo it, that won't be as big of an issue.

Did you purge the system before filling? It's possible you may have moisture in it.

The system was full and working (not correctly) prior to replacing the expansion valve. After replacing the expansion valve I ran the vacuum pump for 45 minutes to make sure there was no moisture in the system.

 

[JoshHefnerX]

Every time I've had high pressure on the high side it's because the condenser wasn't getting enough airflow past it. Can test by running a hose over it to lower the temps, see what it does. Could be tied to your fan problems.

Edit, just reread one of your posts.. Is the fan not running anytime the a/c is engaged? Thought most vehicles were setup to run fans as the ac was running.

 

[r3dd0g]

Every time I've had high pressure on the high side it's because the condenser wasn't getting enough airflow past it. Can test by running a hose over it to lower the temps, see what it does. Could be tied to your fan problems.

Edit, just reread one of your posts.. Is the fan not running anytime the a/c is engaged? Thought most vehicles were setup to run fans as the ac was running.

The fans are controlled by the Holley Dominator as they are PWM fans. For cooling the condenser I have it programmed to sense an input from the trinary switch I installed on the A/C high pressure line, this has 4 connections. One set is in line with the compressor, if pressure is too low (28psi) or too high (384psi) it disengages the compressor clutch, this +12V signal also goes to the dominator to do a 30% IAC kick. The second set is for controlling the fans, one wire is grounded and the other goes to the Holley, when pressure hit's 227psi these contacts close and the Holley turns the fans on, at 185psi the contacts reset and the Holley will turn off the fans.

The issue I was running into before I pulled out some of the refrigerant was that revving the engine would cause the discharge pressure to spike over the 384psi setpoint and it doesn't reset until it drops to 298psi. However, while looking up the information on my trinary switch to make this post I realized I purchased the R-12 trinary switch. The fan setpoints are the same, but the clutch high pressure setpoints are different, off at 454psi and back on at 369psi. I'm not sure how much this is attributing to my issues, but I'll get the correct one ordered and installed regardless.

With everything set the way it is, the fans kick on when discharge pressure exceeds 227psi. With the fan's running (hood open obviously) the pressure drops back down below 185psi and the fans turn back off and the cycle repeats. The fan's kick on and off every 30 seconds or so and the A/C is kicking out 55F air. The only problems occur when they system gets heat soaked after parking it. I have not managed to get the gauges connected while it was having the heat soak issue and I'm honestly not sure that's possible.

 

[JoshHefnerX]

So you need the fans to turn on immediately on a hot start, to clear out the stagnant heat.

 

[r3dd0g]

The fans will kick on when discharge pressure goes over 227, which should be quick on a hot condenser. They also kick on when coolant temps go over 205F. Initial power is 50% but they ramp up to 100% by 220F.

 

[mrk5]

I don't know how it would work with this year of truck, but in the 73 I put the biggest radiator size they did from the factory. Well at least the modern aluminum and plastic equivalent of what would essentially be a big block radiator with heavy duty cooling. It has the Windstar fans with the Derale PWM controller. If the outside temperature is below 80°, the CTS will not hit 165°. Sometimes it's difficult because it's warm enough to want to run the AC but because the AC kicks the fans on to 60%, the engine will never warm up. I have the grill completely covered for 8 months of the year.

I don't know if they made that kind of radiator for the 67-72 trucks.

 

[r3dd0g]

I have a very large aftermarket radiator, I also have no issues when the outside temps are at 80°F, that's middle of winter temps here . The DeltaPag fans put out 2700CFM each when they go to full speed, the Windstar fans are rated at around 4000cfm total. It sounds like you need a thermostat, no water should be going through your radiator until the thermostat opens up, so fans running should have no effect on cooling.

To be clear, I do not think my truck is running too hot right now. I think it's fine, the blockoff panels I added did lower temps by about 5°F and I don't think an LS really cares about 220°F anyways. My issue is that I plan on adding quite a bit of power and I will be doing some towing as well. I want to optimise the cooling now before it becomes an issue. It's currently 108°F and it's just starting to warm up here. If I want to tow the S-10 up to Payson during the summer, I need better cooling, especially when I add the additional radiator for the intercooler I plan on adding.

 

[Wes Harden]

Personally I would turn the fans on earlier. 185° on, off at 175°. Unless you are running catalytic converters no reason at all, LS or No, to run at those temps.
My 8.1l never goes over 205, just towed a trailer home from Scottsdale, 109°-112°. 220° make me nervous.

I run 1 10" condenser fan any time the compressor clutch is engaged. Main fan is old school mechanical.
The 77 has 2 capillary tubes one is an adjustable temp switch to monitor front evap temps. the other is TEV for rear evap. Both are wrapped around evap exit and insulated with black tar type insulation.

 

[r3dd0g]

The stock thermostat doesn't open until 187°F, having the fans running for anything other than the A/C at lower temps than that is pointless, with your settings they would turn on and never turn off until you shut the truck off. DeltaPag has really good information on programming the fans, they shouldn't kick on until at least 10°F above the temperature the thermostat is fully open and off at least 5°F over that temperature. Running at higher temps = better efficiency, lower emissions, etc. There is no benefit to running an LS engine at lower temperatures unless you're drag racing.

Running a dedicated fan on my condenser is an option, I have the old 16" fans I took off the radiator so I may look into that and leave the big fans programmed only for water temps, assuming I can flip the fan blade anyways.

 

[r3dd0g]

Also as a side note, the high temperatures I'm seeing are from the Dominator using the factory location for the CTS. My Autometer gauge that's in the other head reads 10°F cooler.

It's the same on the Silverado, if I look at my Edge CTS the temps are way higher than what the gauge on the dash shows, even though they're both reading the same sensor.

 

[Babaganoosh]

Are you running the other sensor in the back of the passenger side? I had the same temp difference.

I think you are onto something with the big fan on the condenser in conjunction with the engine fans running PWM. This is one feature I wish the terminator had without a separate module.

Aftermarket A/C just sucks and doesn’t work the same as GM to bad these trucks are so old and brittle it just falls apart.