Fairly new AC system barely cools truck

I finally got around to connecting AC gauges to my truck to get some readings and I put up a video. The best temperature that I could get at idle was 70 degrees at the vents on max cold, while driving down the highway it gets down to 58 degrees.

The temp outside that day was 90 degrees according to my phone although it felt much hotter. The asphalt temp was over 120, the temp on the suction hose was around 77. The gauges showed pressures of 48psi/205psi. While revving the engine by hand the gauges went to 45/270psi.

As a reminder, the AC shop that I took my truck to said that everything looked ok so their conclusion was that the system was overcharged with pag oil.

hekg said:

With help from members on this board I replaced my entire AC system except for the evaporator and lines. Put in a sanden, parallel condenser, accumulator, orifice tube and expansion valve in the rear and I even upgraded my fan clutch to a stronger but louder one.

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It appears you've got a 1996+ Suburban with rear air (please confirm).

It's using a Sanden #4440 compressor (5.12" pulley) to replace the HT6.

You've mentioned "oil" as suspect. Let's focus on the oil containing components.

It appears you replaced the compressor, condenser and accumulator. It appears you kept all the lines and the evaporators.

Did you flush or drain the oil from any of the lines or evaporators?

Did you drain the oil from the compressor you removed, and measure the amount?

How much oil did you add to the accumulator and condenser as you re-assembled the system?

Did you add any dye (oz) or did the system already contain dye?

Account for the oil which comes already installed in the Sanden compressor (IIRC this is 8oz), e.g., you drained as much as you could, you drained none of it, you drained and backfilled with a measured amount,...

Air doors working properly? Air doors in poor condition--don't seal right?

Low-side pressures of 45/48 seem excessively high. Wrong low-pressure cutout switch? Wrong orifice tube? Insufficient air flow through the condenser? (You replaced the fan and fan clutch, but the clutch could be defective, or it maybe isn't being warmed by the radiator so it doesn't engage like it should. And no fan or fan clutch in existence will pull air through a plugged radiator.) Insufficient compressor capacity?

Yes I flushed the system with two of those large flushes from Napa and made sure to follow the instructions carefully. I flushed the lines and evaporator in the front and separately also flushed the rear evaporator and lines.

The only reason that I can somewhat agree with the oil analysis is because when it arrived, I dumped out and measured the oil that the compressor shipped with but it wasn't even half of what it said it should've had in it. I only got about 1.2oz out.
I tried a few more times to get more out of it by holding it upside down while turning the clutch but barely got any more drops out of it so I wasn't always 100% on what I started with when I charged the entire system with the 11 ounces of oil that the C69 Tahoe calls for.

Can 1 or two ounces of additional oil cause the system to cool so poorly though?

Schurkey said:

Air doors working properly? Air doors in poor condition--don't seal right?

Low-side pressures of 45/48 seem excessively high. Wrong low-pressure cutout switch? Wrong orifice tube? Insufficient air flow through the condenser? (You replaced the fan and fan clutch, but the clutch could be defective, or it maybe isn't being warmed by the radiator so it doesn't engage like it should. And no fan or fan clutch in existence will pull air through a plugged radiator.) Insufficient compressor capacity?

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You make some very interesting points. The AC shop that I went to tested by clamping the heater hoses off but the vent temps didn't drop at all so he assumed that the doors where working ok.

The ac compressor clutch never disengages so I assume that the low-pressure cutout is ok. The orifice tube is the white and yellow one recommended for the C69 dual air trucks and I installed it in the line closest to the accumulator and not in front of the condenser.

The radiator fan clutch seems to be cooling ok because the engine temps are always on the cooler side at all times and the fan is now annoyingly loud compared to with the previous stock fan clutch.

Insufficient compressor capacity? I went with a popular Sanden model with obs owners, unless I got a weak compressor from the factory which is always a possibility.

I swear I thought that this was going to be and easy project but boy was I wrong. It was fun to install it all myself but I thought that it was going to freeze me out on the first try.

hekg said:

Yes I flushed the system with two of those large flushes from Napa and made sure to follow the instructions carefully. I flushed the lines and evaporator in the front and separately also flushed the rear evaporator and lines.

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Did you use a high-vol or low-vol flush?

Did you vacuum the system long-enough to remove any residual flush?

Could you smell the scent of the flush in the exhaust from the vacuum pump?

Did you find the need to change the vacuum pump oil in order to pull full vacuum?

Did you turn off the pump and close the manifold valves and let the system sit for hours (overnight) to see if vacuum would hold steady?

hekg said:

Insufficient compressor capacity? I went with a popular Sanden model with obs owners, unless I got a weak compressor from the factory which is always a possibility.

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The Sanden #4440 (155cc/rev, 5.12" pulley) is "popular" with the trucks. The Sanden #4261 is the same as the #4440 but w/ a smaller pulley (4.41"). It's what I used in my Suburban to provide addn'l pumping capacity.

@L31MaxExpress has found an even higher-capacity Four Seasons HT6 replacement, p/n 88947, 210cc/rev, 4.25" pulley.

The stock HT6 compressor is 165cc/rev (10 cubic inch), 5" pulley.

hekg said:

The only reason that I can somewhat agree with the oil analysis is because when it arrived, I dumped out and measured the oil that the compressor shipped with but it wasn't even half of what it said it should've had in it. I only got about 1.2oz out.

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The Sanden spec sheet (attached) says it comes with 135cc (4.5oz) of oil. ACKit's WWWsite lists the same spec. Yours may or may not have had that amount. Sanden says a drained compressor will retain about 0.5oz of oil, so you can probably count on having that much (or possibly more).

hekg said:

I wasn't always 100% on what I started with when I charged the entire system with the 11 ounces of oil that the C69 Tahoe calls for.

Can 1 or two ounces of additional oil cause the system to cool so poorly though?

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If you believe you have too much oil, you can always try Sanden's oil test in Section 6.8.3 of their service guide (attached) to see if the proper amount is resident in the compressor.

1998_K1500_Sub said:

Did you use a high-vol or low-vol flush?

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I couldn't say the type but I bought these cans from Napa TEM 419955.

1998_K1500_Sub said:

Did you vacuum the system long-enough to remove any residual flush?

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Actually I only vacuumed for about an hour and then just let it sit for another hour afterwards to test for leaks and it held perfectly in that amount of time and since it was a new vacuum pump it was running on it's first fresh oil fill. I do not remember the smell of flush coming from the pump but then again I wouldn't have even recognized it.

1998_K1500_Sub said:

@L31MaxExpress has found an even higher-capacity Four Seasons HT6 replacement, p/n 88947, 210cc/rev, 4.25" pulley.

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I'm almost wishing that my compressor is the problem so I can replace it with one of these but it was brand new in the box.

hekg said:

I couldn't say the type but I bought these cans from Napa TEM 419955.

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That p/n is a high-vol flush, so it's less likely to leave some residual in the system.

hekg said:

Actually I only vacuumed for about an hour and then just let it sit for another hour afterwards to test for leaks and it held perfectly in that amount of time and since it was a new vacuum pump it was running on it's first fresh oil fill. I do not remember the smell of flush coming from the pump but then again I wouldn't have even recognized it.

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That's a good sign, it's unlikely IMHO that any flush remained in the system.

hekg said:

I replaced ... expansion valve in the rear

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Need I ask: Did you attach the TXV's sensing bulb appropriately to the suction tube of the rear evaporator? I'm wondering if the rear TXV is hanging open.

1998_K1500_Sub said:

That p/n is a high-vol flush, so it's less likely to leave some residual in the system.



That's a good sign, it's unlikely IMHO that any flush remained in the system.



Need I ask: Did you attach the TXV's sensing bulb appropriately to the suction tube of the rear evaporator? I'm wondering if the rear TXV is hanging open.

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I just realized that you asked about the sensing bulb on the rear txv. I attached it exactly the way it was on there originally but it won't hurt to take a look just to make sure that it's on there correctly.

Since the consensus seems to be that my system has too much oil in it would it be safe to assume that I can just resolve this by getting rid of the accumulator and putting it a new one without adding any oil it? This way I'd be removing oil from the system and then wouldn't have to take everything apart to flush every component separately.

Does the accumulator usually contain much oil in it at any given time? Say more than 3 ounces?

hekg said:

Does the accumulator usually contain much oil in it at any given time? Say more than 3 ounces?

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The service manual suggests the accumulator might have 3.5oz of oil. See their comments at the top right of the attached page.

You might try cutting it open after removal, in some sort of attempt to confirm the volume.