A/C Question
 

Hello I am new to the forum, I am need of an A/C Techs suggestions. I have 94 full size Blazer, I was wondering how many ounces of refrigerent(r-134) this truck typically holds, Autozone says 36 ounces. Well I installed a new valve kit, needless to say I needed to refill it. I added 3 cans (36 ounces) and the compressor would cycle off due to low pressure below 20 psi on the suction line at 1000-1500 rpms, so I added about another 12-15 Ounces and it didnt cycle off and the temp in the cab reads about 41-45 degrees when driving but the psi still drops close to 20 psi on the suction line when I rev it to 1500 rpms, I was under the impression it should maintain around 30 psi on average at that rpm range.... whats even more strange to me is the return line seems to be within the proper psi range @ ambient temp. does any one know what could cause this issue or is this normal? thanks

just get A GAUGE and keep fitt till its in the green

If you don't have a gauge there should be a sticker on the unit around the receiver/drier that tells you. My 98 Tahoe said 39 oz.

I've got a pretty nice set of auto a/c gauges, my concern is what could be causing it to need more refrigerant than is recommended. I was thinking maybe i need to replace the drier?? I'll check on the drier for a capacity sticker...thanks. I took a road trip and while on the interstate it held a constant 41 degrees which is'nt bad, but something isnt quite right with the suction pressure.

I have a 94 S10 Blazer. Haven't looked at the sticker but the S10 Blazers came with R-12 originally. Not sure about the full size models. The S10 pickups came with R-134a

The 94 came out with R-12? Because I know they outlawed it in 94 but didn't know if it was before the model year came out or after.

The S10 Blazers had R-12 and the S10 trucks had R-134a. That's per the factory Service Manual. You can tell on mine because someone before me did the conversion (easy to tell by looking at the gauge connections). That's the year they went to Gen 2 on the tricks and the last year for Gen 1 Blazers. You ought to wade through the Driveability and Emission/Wiring Diagrams Manual for that year. You have to pay real close attention.