Re: 1988 corvette, don't understand what it's doing?
Posted: Sat Jun 06, 2020 5:32 pm
So I've been digging around while waiting for parts. A couple issues have arisen.
1. Charge. My FSM ( real, not haynes or clymer) lists the charge for R12 (original fill for my 88) as 2.75 lbs. Labels on the car agree with the FSM. BUT.....while digging around in the TSB's for an 88 corvette, I came across a very short and brief service bulletin that CORRECTS the FSM. Seems GM spec'd the 88/89 Vettes at 2.25 Lbs, not 2.75 lbs as listed in the FSM and on the car labels. Somewhere along the way they had a printing error I guess, or someone at GM just plain effed up and incorrectly spec'd 2.75 lbs. So I would have been overcharged by at least .5 lbs if using R12, the equivalent of half a can of redtek (by their equivalency charts). Not sure if that was my whole problem, but it sure as heck wasn't helping it. No matter how you slice it, I was overcharged, by a fair amount. Seems to fall in line with most of the symptoms/problems I was having.
2. Cycling switch. Well, seems an r12 switch was set for around 25 psi and the R143A switches (later years) were set at around 20-22psi. Looking at the Redtek charts, it looks like it wants to be somewhere down around 20 psi. I've read several comments around the web that because of redteks temp glide, it's hard to say where the switch should be set and it's more of a "try it and see" deal to get a good setting.
As to which switch is already in my Vette, who knows? it could be either. I have no idea if anyone has ever changed it. Seems like a likely thing to have been changed as the car is 31 years old. No telling who has done what to it in it's past.
Luckily, The low cycling switch on my Vette actually has an adjustment screw. So once I get it up and running, at least I can adjust the CCOT so the evap doesn't freeze up and it will cycle properly for the r12a.
Of course, I've got to getting it working first (even if it's "crappily") before getting to the switch adjustment.....
1. Charge. My FSM ( real, not haynes or clymer) lists the charge for R12 (original fill for my 88) as 2.75 lbs. Labels on the car agree with the FSM. BUT.....while digging around in the TSB's for an 88 corvette, I came across a very short and brief service bulletin that CORRECTS the FSM. Seems GM spec'd the 88/89 Vettes at 2.25 Lbs, not 2.75 lbs as listed in the FSM and on the car labels. Somewhere along the way they had a printing error I guess, or someone at GM just plain effed up and incorrectly spec'd 2.75 lbs. So I would have been overcharged by at least .5 lbs if using R12, the equivalent of half a can of redtek (by their equivalency charts). Not sure if that was my whole problem, but it sure as heck wasn't helping it. No matter how you slice it, I was overcharged, by a fair amount. Seems to fall in line with most of the symptoms/problems I was having.
2. Cycling switch. Well, seems an r12 switch was set for around 25 psi and the R143A switches (later years) were set at around 20-22psi. Looking at the Redtek charts, it looks like it wants to be somewhere down around 20 psi. I've read several comments around the web that because of redteks temp glide, it's hard to say where the switch should be set and it's more of a "try it and see" deal to get a good setting.
As to which switch is already in my Vette, who knows? it could be either. I have no idea if anyone has ever changed it. Seems like a likely thing to have been changed as the car is 31 years old. No telling who has done what to it in it's past.
Luckily, The low cycling switch on my Vette actually has an adjustment screw. So once I get it up and running, at least I can adjust the CCOT so the evap doesn't freeze up and it will cycle properly for the r12a.
Of course, I've got to getting it working first (even if it's "crappily") before getting to the switch adjustment.....