1999 GMC Yukon

[Cusser]

I wonder why GM would apply it to the accumulator, a part that would normally be replaced every time the system is opened for whatever reason (and the decal lost after the first replacement).

Because it's GM.

Agree that it's a dumb location.

[Mark86]

I left the system under a light nitrogen charge as I had to leave town for few days, I will charge it when I get back home. I've got a 2000 3500 Silverado Dually crew cab which was my father's also, which I'm driving back to Phoenix this week, which will be next in line for some AC tune up. My dad bought this truck new and it has 56k miles. It has the same circle sticker (different specs) on the accumulator and the same piece of shit HT6.

I'll take some accurate temps and pressures so we can discuss.

[JohnHere]

Okay, good.

I recommend leaving the '00 Silverado Dually alone until you get the '99 Yukon A/C system running well.

Does the A/C work in the Dually?

[Mark86]

I'm not sure. I turned it on and it appeared to be short cycling but it was pretty cold. I unplugged the compressor for my journey as I would need the defrost and didn't want to run the compressor with an unknown charge or condition. Didn't want any issues in that regard.

I did break down in Raton New Mexico. Truck died in the Subway sandwich parking lot. Would crank but wouldn't start. Luckily I brought my scanner with me. Crank position sensor. I walked to Oriely's and bought some tools and the sensor and was back in business. I called three shops and asked if they could send a mechanic to pick up the part and come by and install it and all three said no. "They didn't do that kind of thing". I said I would pay triple the rate and they declined.

Im going to pull the lower fan shroud in that 99 Yukon and change out the lower rad hose. Looks tired and original. So maybe a few days before I charge up the Yukon.

[Mark86]

Hey guys, sorry for the long delay in getting back to this post. Work, family, holidays, etc. Before I wanted to test the system I wanted to verify that no mice had gotten into the HVAC system. So I pulled blower motor and inspected what I could see with a mirror the evap and then vacuumed out years of minced leaves and debris.. I pulled the front dash off as well as the lower valance. I used a leaf blower and moved the modes to blow every duct clean, or at least verify a pile of nesting material didn't come out. I then used AC forming cleaner to fill the duct work, up the evap drain hose, in the blower motor opening etc. let sit and towels placed at the floor accepted the drippings. Installed the blower motor hooked up a battery charger and let the motor run while I put the dash back together. I also had to replace the blinker combo switch while I was in there.

Today I purged the system of the nitrogen head I left in there, vacuumed it down for an hour and charged with 44.2 oz. Here are the numbers and specs.

Clutch fan - New GM OEM.
Condenser - OEM 1" thick, no fin damage, looks new.
Orifice tune - Cleaned and reused original, installed in Y pipe to front only.
Compressor - Sanden New.
Rear - untouched, OEM as far as I know, now receiving liquid refrigerant.

Temp in my garage 77*F, engine idle, windows open, max AC with recirc on fan high / rear AC on high fan
Charged with 44.2 oz 134A as a gas. (Took a while).

Wasn't too hot today, and evening is here so a true HOT load test will have to be done latter.

Engine RPM IDLE.
high side = 135 psi.
low side = 28 psi.
front vent (middle of dash) discharge = 39.5*F
Irear (overhead only) discharge = 42*F

2000 RPM (equal time off and on cycle)
High side = 163
Low Side = 19
Front vent = 38*F
Rear vent = 43*F

[Carguychris85]

You are a solid 20oz light on refrigerant. I had the same vehicle, 99 Tahoe and it required 64oz.

Factory condenser is absolutely inferior compared to a parallel flow of the same width/height despite the parallel flow being a fraction of the thickness. Installed a parallel flow in both my Express and G20 vans. They both cool far better than they did with the junk OE condensers. The thick factory serpentine style block a ton of airflow through the cooling stack and do not reject heat as well from the refrigerant as a true parallel flow does. It took me owning a 2002 Express with an OEM parallel flow condenser to understand just how much better it worked than the serpentine style in my 1997 Express.

That Sanden is going to really struggle in any weather over about 90F.

Will also add a tip on a parallel flow update from the older, larger GM serpentine conde sers, the refrigerant capacity changes. The factory refrigerant capacity is no longer accurate when the system setup changes.

For example GM went from 48 oz to 32 oz on the front air only Express vans when they updated that model to a parallel flow condenser in 2002. Same system, just a condenser change and suddenly 16oz less charge. On my 97 Express with a parallel flow condenser upgrade, I used the 2002 front refrigerant spec and added the charge amount in the instructions for the aftermarket rear ac. Been ice cold ever since.

[JohnHere]

You are a solid 20oz light on refrigerant. I had the same vehicle, 99 Tahoe and it required 64oz.

I agree with Carguychris85. Every specification that I have says the following: 64 ounces net weight of R-134a, and 11.0 fluid ounces of PAG-150 for an OE Harrison compressor. If you have an under-hood decal that has different specs, the decal always takes precedence.

[Mark86]

The condensor installed is a parallel flow. The first condenser I purchased was an OEM equivalent (Dorman) and it was as thick, but was a serpentine design. I am unsure of the service history or this vehicle so I assumed it was OEM. Evidence suggest otherwise. It's in excellent shape which also suggest it's probably not OEM for the age and mileage.

After some thought and initial charge numbers I think that accumulator sticker is deceiving. Suburban may indicate C69 and Tahoe Yukon may imply the two door "full size blazer" variant which never came with C69, just C60, front only AC. The factory charge for a 2 door Yukon is 44 oz.

It's pretty cool here in Phoenix, and it's not short cycling. I think I will charge up to the 56 oz and see where the pressures go. I can recover via weight as well, so I'm not concerned about over charging, I can take it back out as well.

If that sanden is under powered for this system, would it be OK for a single system? I've got a 2000 crew cab that will need a compressor as well, and I could go back to the OEM Harrison for the Yukon.

[Mark86]

You are a solid 20oz light on refrigerant. I had the same vehicle, 99 Tahoe and it required 64oz.

I agree with Carguychris85. Every specification that I have says the following: 64 ounces net weight of R-134a, and 11.0 fluid ounces of PAG-150 for an OE Harrison compressor. If you have an under-hood decal that has different specs, the decal always takes precedence.

Post 9 on the first page has an image of the OEM charge decal which is on the accumulator I replaced. Cryptic and not a good place for a permanent decal. If the condenser was replaced, I'm sure the accumulator was as well. Maybe at a GM dealership and an OEM accumulator was installed, hence the generic accumulator sticker.

[Cusser]

You are a solid 20oz light on refrigerant. I had the same vehicle, 99 Tahoe and it required 64oz.

I agree with Carguychris85. Every specification that I have says the following: 64 ounces net weight of R-134a, and 11.0 fluid ounces of PAG-150 for an OE Harrison compressor. If you have an under-hood decal that has different specs, the decal always takes precedence.

I replaced the AC compressor on our 2005 Yukon Denali XL with rear AC, and added about 64 oz. R134a. I had a compressor slugging issue on it. I used an OEM compressor, did not touch its condenser due to cooling performance when it wasn't slugging. Was fine after that, no slugging or broken AC belts.

You have the Sanden/SD replacement compressor, so that should not affect the total refrigerant capacity much or at all.