77 Pontiac Trans Am 400 V8 A/C vibration issues
Posted: Sat Jul 01, 2023 10:43 am
When I restored my 77 T/A the A/C was converted to 134a. A 5H14 Sanden compressor was installed along with a new factory condenser. The system was flushed, a new O/T installed, 8 hour vacuum pulled and it held before charging. Pressures at 2000 rpm were 225 and 25. Ambient was around 75F. Discharge temp was 40F.
The issue is a bad vibration that occurs just off idle and at around 2750rpm. The vibration is felt and can be heard though the entire vehicle. As soon as the A/C is turned off, the vibration and noise are gone.
When the vibration occurs you can see it in the belt. According to Continental the belt tension should be a 100 psi. I adjusted it form 55 to 90 but was afraid to go any tighter as the belt was extremely tight. At that tension the vibration was less but still there. The belt has been replaced.
I have made sure that the compressor mount is as solid and tight as it can be, and that the pulleys are parallel and in line. I installed a new drive pulley since the wear pattern in the groove was not uniform.
I am on my second compressor since the company that the system was purchased from recommenced that. The company is a major supplier of conversion kits.
Originally there was a muffler in the discharge line, but it was not used when the system was converted. I have the muffler and am wondering if that would help with possible pulsation from the compressor. As I understand it, typically the Sanden compressor doesn't require a muffler.
The condenser is not parallel flow. I am wondering if changing to that would help.
Lastly, since the distance between the two pulleys is pretty far, it would seem that a back side idler would possibly be beneficial. I have searched for one that could be retrofitted to the system but haven't found one yet. I have not seen any vehicles similar to mine that requires that though.
The company that the conversion kit was purchased from says that everything is textbook, they have never run into that and have no idea what is causing the issue.
The issue is a bad vibration that occurs just off idle and at around 2750rpm. The vibration is felt and can be heard though the entire vehicle. As soon as the A/C is turned off, the vibration and noise are gone.
When the vibration occurs you can see it in the belt. According to Continental the belt tension should be a 100 psi. I adjusted it form 55 to 90 but was afraid to go any tighter as the belt was extremely tight. At that tension the vibration was less but still there. The belt has been replaced.
I have made sure that the compressor mount is as solid and tight as it can be, and that the pulleys are parallel and in line. I installed a new drive pulley since the wear pattern in the groove was not uniform.
I am on my second compressor since the company that the system was purchased from recommenced that. The company is a major supplier of conversion kits.
Originally there was a muffler in the discharge line, but it was not used when the system was converted. I have the muffler and am wondering if that would help with possible pulsation from the compressor. As I understand it, typically the Sanden compressor doesn't require a muffler.
The condenser is not parallel flow. I am wondering if changing to that would help.
Lastly, since the distance between the two pulleys is pretty far, it would seem that a back side idler would possibly be beneficial. I have searched for one that could be retrofitted to the system but haven't found one yet. I have not seen any vehicles similar to mine that requires that though.
The company that the conversion kit was purchased from says that everything is textbook, they have never run into that and have no idea what is causing the issue.