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'98 GMC Suburban

finalapproach on Thu November 29, 2007 10:24 AM User is offline

Year: 1998
Make: GMC
Model: Suburban
Engine Size: 7.4L
Ambient Temp: 75
Pressure Low: 40
Pressure High: 250
Country of Origin: United States

I really need some input to a problem with the front AC on a '98 Suburban (with rear AC).

When running the AC on MAX, the temp. output from the front vents is not cold. The rear output is working fine.
I obviously figured there was a problem with the heater-core water cut-out valve, so I verified that it was working correctly (and actually connected it directly to the engine vacuum so it would be held closed). The blower is fine and the volume of air is fine. The air is chilled, just not what it should be (or at the temp of the rear output).
Why would there be this discrepancy if the front and rear systems are essentially running in parallel?


Thanks, Bob

Chick on Thu November 29, 2007 11:10 AM User is offlineView users profile

Sounds like a clogged O tube in the front, I would recover the refrigerant and pull/change the O tube. What it looks like will determine how much work is going to be needed. Your pressures are to high for that ambient which would also indicate a blockage. Was any thing done to the system? Anything added, like sealers? If the system is clogged, you may be looking at a system flush and changing the condenser and O tube/expansion valve, new oil etc..Let us know everyting that was done...or if nothing was done, when the problem began..

When you recharge, pull a deep vacuum and charge the system amount (oin the underhood sticker) back into the vacuum, no more than that..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

GM Tech on Thu November 29, 2007 2:47 PM User is offline

When the system is recovered- take note of how much came out- the number one failure mode of A/C systems is loss of refrigerant- could be you have 1/2 of necessary charge in your system- and rear responds better on low charge than front- your compressor is known for leaks at the belly of the unit- if you are low on charge- I'd suspect that area as the source of the leak..............

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Chick on Thu November 29, 2007 3:19 PM User is offlineView users profile

As GM Tech stated, a loss of refrigerant could have been the root cause of a failure, you need the full charge to move the oil.. No refrigerant, no oil movement, compressor goes clogging the O tube, conndenser, contaminating the oil thats left. This picture should help you see if you have a belly leaker as GM Tech stated. It may be "extreme" but will give you an idea where to look. If a compressor replacement is necessary, I highly recommend the "Seltic/Valeo" clone. I use on on my own car and could not be happier. You can e-mail the guys at Ackits.com The pic of the belly leaker was mine... The pic below is the valeo clone... Once you find out the cause, and if it's clogged, post back and we can give you the step by step repair procedure..Hope this helps..



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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

finalapproach on Sun December 02, 2007 9:31 PM User is offline

Thanks for all the feedback. I had the compressor replaced a few years ago (along with the "usual" parts). It worked fine right up until this summer.
It's winter here (NY) now, so it may not be a priority to get to this right away. I'll take your advice... check for leaks (and possibly replace the compressor) and do a flush and re-fill.

THANKS!!!!

Chick on Sun December 02, 2007 9:37 PM User is offlineView users profile

Check for leaks, but don't change the compressor unless it needs it... I live in New Jersey, so yes I know it's a little to cold to be concerned with cooling right now..Was around 20 to 24 all day.."Cold enough".. If you don't find signs of the leak, have the refrigerant recovered and recharged with some UV dye, that will help you find the leak then you can fix it properly..Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

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