I have a 07 chevy tahoe. My front ac blows cold( but it struggles to keep cab cold) and my rear ac is not, only blows lukewarm. I touched my front pipe by the dryer and it was pretty cold (as i am in tx in 97Degree fahrenheit), then went back to the pipe where my rear expansion valve are and it was lukewarm (not cold or not too hot.) As i was touching the rear ac pipe i felt that some cool air was escaping from the rubber seal that goes around the expansion valve, plastic is really worn out and some pieces missing would tgat be a issue? any help is appreciated. I was thinking either my expansion valve could be clogged up? Want to make sure before i start disassembling. Thanks !!
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Welcome to Motor Vehicle Maintenance & Repair!– Pᴀᴜʟsᴛᴇʀ2 ♦Commented Jun 26 at 22:58
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2 Answers
This system needs to have manifold gages hooked up to it. This will give an indication whether it's low on refrigerant or has a bad expansion valve or compressor or any combination of these. Without doing this, guesses can go on all day. An experienced tech can pretty much give a reliable diagnosis with the gage readings. It is automatic to also check for leaks. From the description, my guess would be a bad expansion valve plus a possibility of low refrigerant. But you must start with the gages.
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All vehicle ac systems will suffer the #1 problem; a leak or leaks after several years of reliable cooling. System configuration demands aluminum parts to save on weight and aluminum is inherently soft, work hardened after rough road conditions vibrate thru suspension. A big mistake is running to auto stores for the refill kit containing sealer in hopes of an inexpensive repair from a can, more often than not refilling doesn't fix a leaking system. Sealer contaminates and may lead to a more expensive repair requiring rebuilding; replacing compressor, condenser coil, thermal expansion valve(s), receiver/accumulator/drier, etc. Remove both service valve caps and check for the presence of dye (greenish yellow) and oil. GM installed dye for easier leak detection of sealed systems. If you see dye in the service ports, buy an inexpensive uv blacklight and inspect the entire system, looking for dye marking the leak site. Then determine whether you can make repairs requiring parts and new O-rings for every part replaced. Use the blacklight in shade, indoors or at night to allow dye to glow from uv illumination. Shine it at dye in service ports to see how bright it is. Refrigerant, oil and dye circulate continuously throughout a system and when a leak occurs, invisible refrigerant, oil and dye leave with oil and dye leaving markers. Service valves wear out and may leak (caps help with sealing), fittings crack, crimped fittings leak, punctures can occur in the condenser coil, aluminum tubing cracks, etc. Compressors and thermal expansion valves rarely fail; losing refrigerant means less to zero cooling and enough refrigerant loss triggers the pressure senor to send a disable signal to the ecm to prevent compressor operation; oil won't return to lube the compressor, resulting in immediate damage. Find and fix the leak and restoration of factory cooling can return. Losing about half its refrigerant may allow compressor operation but little to zero cooling. Refrigeration gauges are a must whether commercial or diy repairs. Gauges and electric vacuum pumps may be free loaners from Autozone or other auto stores.
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The rear AC shares the same refrigerant charge as the front. This problem WILL NOT be caused by a leak. If it were leaking in the rear, it wouldn't blow cold up front. If it were leaking enough to cause an issue, the compressor wouldn't even turn on.– Pᴀᴜʟsᴛᴇʀ2 ♦Commented Jun 26 at 22:57
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I respectfully disagree and aware that many large suvs and minivans have dual evaporator coils, two separate hvac housings to enable cooling for large interiors powered by one compressor. The op mentioned struggling front cooling and zero cooling in the rear evaporator coil. This strongly suggests loss of refrigerant.– F DryerCommented Jun 27 at 0:36
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The problem is Chevy Tahoes (To include GMC Yukon, Yukon XL, & Suburban) only have a single source of refrigerant. They share refrigerant front and rear, regardless of separate evaporators. The OP states the front is having a hard time cooling the entire cabin but is still cold, that's because normally the cabin would be cooled by the two evap coils and now is only being cooled by one. It is more likely the expansion valve to the rear is plugged as the OP suggests.– Pᴀᴜʟsᴛᴇʀ2 ♦Commented Jun 27 at 12:53
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Dual expansion valves for dual evaporator coils. A single compressor with capacity to handle two evaporator coils configured for large interiors with more window area, whether with or without factory tinting, has a larger refrigerant capacity. Very few diyers familiar with refrigeration gauges are capable ot determining failure of expansion valves, loss of refrigerant or compressor failure. I prefer suggesting leak detection first and proceeding with gauge hookups second if leaks are not found before dismantling a system on a guess. Once opened, all refrigeration repair procedures are needed.– F DryerCommented Jun 27 at 13:00
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1Thanks guys, got it hooked up to gauges. No leak just orfice tube was really dirty.– CarlosCommented Jun 28 at 15:49