I converted my 1991 foxbody 5.0 lx to r132 bought everything brand new from summitracing I kept the manifolds off the old r12 compressor and used them on the new r132 compressor all new seals everywhere and it lasted a month and started blowing warm air not sure why ...do I need to install those compressor manifolds from LMR?
No, you don’t need the manifolds unless yours are damaged/corroded where the o-ring creates the seal. If there is any damage that would compromise that seal, then they should be replaced.
You have a leak somewhere on the system and need to find it.
I skip the dyes and lights and go right to the Sniffer.
I used a TIF XL-1 which works quite well for R-12/R-134a and has found tiny leaks. You can get these on EBay for $50 used. It’s just much faster.
If you system is empty you can squirt a little R134 in the system (if you have converted and have compatible oil). Just enough for positive pressure. Then you can sniff around and try and detect the leak.
A very common leak point is the shaft seal on the compressor (I know you said yours is brand new) and a clue might be oil residue on the snout of the compressor under the clutch area. This area leaks with r12, so it definitely will leak with the smaller 134a molecule. The sniffer does a good job here.
Like said, R-134a is smaller than r12, so all the o-rings in the system need to be changed out to the green style that is compatible with 134a. (Already done with kits and every new line you buy these days.) Problem is to change the shaft seal, the entire compressor needs to be disassembled. Many folks skip this, so when the system leaks out again, it’s likely this spot that is the source of leaking.
