My 99 Tahoe's AC is cold up front but hot in the rear

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hekg

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I haven't heard of anyone swapping out just the compressor clutch and getting good results. Maybe I'll swap the clutch out first before I get a whole new compressor.
 

1998_K1500_Sub

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I haven't heard of anyone swapping out just the compressor clutch and getting good results. Maybe I'll swap the clutch out first before I get a whole new compressor.

Since your compressor is running all the time anyway, the clutch, if it was slipping any significant amount (i.e, enough to cause significantly reduced compressor pumping), would be hotter then hell.

That's my $0.02.

Pinching off the rear HP AC line, as I mentioned earlier, would identify whether the TXV is hung open. This test is about the easiest thing you can do right now to convince yourself that the TXV is / is not contributing to the problem.

But I won't be offended if you blaze your own troubleshooting trail.

If you decide to get a new compressor, I suggest the Sanden #4440 and not the OE HT6. A genuine Sanden can be purchased on-line, e.g., from www.ackits.com and others. Sanden wanna-be, clone, knock-offs can be found too, for a bit less money. I bought the real deal.
 
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HotrodZ06

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I went and looked at my suburban with rear air and it appears that a blocked accumulator would still allow the rear to cool. The bad part is all theory until the problem is solved. Blocking of the rear a/c line like 1998_K1500_Sub suggested would provide some answers for sure, without discharging the system.
 

1998_K1500_Sub

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I replaced the expansion valve in the back and the rear AC blows cold again.

OP, was the new TXV’s sensing bulb properly attached to the evaporator’s low pressure pipe? IIRC a spring steel clip is used to hold the two together.

If that bulb isn’t in contact with the pipe it’ll flow excessively.
 

Dariusz Salomon

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That one is easy. The expansion valve in the rear is either plugged up with crap or otherwise stuck closed or potentially even the lines under the truck are damaged or have become obstructed internally. Either way its a restriction in the rear refrigerant loop.

On a system that has an orifice tube up front and an expansion valve in the rear, if the refrigerant level is low, the expansion valve will open fully, hog all the refrigerant flow and the rear will be ice cold while the front is warm. Tahoes do not have rear heat, so there are no blend doors to act up.
If the lines to the rear were damaged the whole ac would empty-but expansion valve like you said,is probably clogged.
 

Dariusz Salomon

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I added three 12oz cans and stopped there because the low pressure gauge was at 75psi and the high was at 225-230psi. I didn't want to overfill or cause damage.

I've read on a few posts that these trucks with rear air require 64 oz of refrigerant and that's what I was planning to put in until I saw the low pressure going that high since every video that I've watched always says to keep the low pressure under 50psi.
Mine is on 1700g(59oz) in a tahoe,and pressures remained healthy-12 oz is way too low. Rear takes a while to cool down even with healthy ac
 

hekg

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OP, was the new TXV’s sensing bulb properly attached to the evaporator’s low pressure pipe? IIRC a spring steel clip is used to hold the two together.

If that bulb isn’t in contact with the pipe it’ll flow excessively.
Yes the sensing bulb was well attached and I attached the new one the same way again.
 

hekg

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I will try the pihnching the line in the rear trick. I was also looking at this Delphi CS0120 since I need to spend some amazon credits.

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Cadillac Bob

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After living in Phoenix for 5 years I learned quickly to park in the shade as often as one can!! Now back in Michigan weather is less hot but way more humid and thicker air but wife always ponders why I’ll pull up or park in certain spots because of the shade we’re going to be out all day garage sale’n the ride need not be having to work harder than needed on hot summer days 85-95 degrees with 75+ humidity is killer but she’s slowly starting to understand that logic! Lol
 

HotrodZ06

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I will try the pihnching the line in the rear trick. I was also looking at this Delphi CS0120 since I need to spend some amazon credits.

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You might check rockauto I believe its quite a bit cheaper for the same compressor plus they provide a 5% discount code on the forum.
 
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