New AC System Doesn't blow cold enough / 68 Polara 383

GMPolara

GMPolara

Member
Joined
Dec 17, 2023
Messages
56
Reaction score
34
Location
SC
I'm having some problems with my newly rebuilt AC system. It's not blowing cold enough. I've changed it over to 134a.

Simultaneously, my engine has developed an overheating problem. I attribute this to not having installed the correct water pump. This engine (383) has two water pumps available for it. One of which is specifically for car's with AC. Which is not what I have in there right now. :) I'm fixing this currently.

I'm thinking that maybe an extra fan in-front of the Condenser may help with my AC problem. But I'd like some other opinions on this. CALLING ALL HVAC FOLKS!

Here's a video that goes through the details about the new AC system:

Dropbox
 
Last edited:
Do you have a clutch fan and a shroud on it now? It should all be working properly and may help your a/c and heating up problems as long as all is well with your cooling system. I wouldn't condemn the pump until you check out the rest of the system.
 
With the a/c 6-blade water pump, the drive ratio also increases to move about the same amount of water as the 8-blade non-a/c pump does at the lower drive ratio that pulley set has.

Is the system charged to about 90% of the R-12 charge level with R-134a? Is the "lesser cooling" happening sitting still or on the road? Stock condenser or an R-134a rated mass flow condenser?

CBODY67
 
Toolmanmike said:
Do you have a clutch fan and a shroud on it now? It should all be working properly and may help your a/c and heating up problems as long as all is well with your cooling system. I wouldn't condemn the pump until you check out the rest of the system.
Click to expand...
Yes, it's got a clutch fan and a fan shroud. I currently, have the a new clutch in hand. The old one was working but a it's action was a little too loose for my taste.
 
GMPolara said:
Yes, it's got a clutch fan and a fan shroud. I currently, have the a new clutch in hand. The old one was working but a it's action was a little too loose for my taste.
Click to expand...
Bolt that baby on and see what happens. If they are loose there's a good chance it isn't locking up when needed.
 
CBODY67 said:
With the a/c 6-blade water pump, the drive ratio also increases to move about the same amount of water as the 8-blade non-a/c pump does at the lower drive ratio that pulley set has.

Is the system charged to about 90% of the R-12 charge level with R-134a? Is the "lesser cooling" happening sitting still or on the road? Stock condenser or an R-134a rated mass flow condenser?

CBODY67
Click to expand...
I hear you on that water pump. I'm just grasping for straws.

I've put about five six once cans in. But I had a leak initially. I'm not sure how much leaked out. Currently, I'm just going by the gauge pressure. Per the low side gauge, I'm at 50psi @95F. I would guess I'm overcharged but the last can I loaded went in like duck shite. Also, the compressor is still nice an quite. Not exactly a scientific explanation, but hopefully that gives you the picture.

The condenser was rated for R134a. It cools best while going down the road, appox. 65F. It seems to get warmer when I accelerate. At idle it's near cool but not cold 65/70F.

Things that I feel might be a problem are that the new Evaporator is OEM design and so is the expansion valve.
 
Last edited:
What pressures are you seeing when the system is on, windows down and set for full cold and max A/C? Also, report the register (interior vents) temperature.
 
I have also seen capillary tubes taped on low side tube surface and heard them working. Factory material shows that they originally go inside thermowell immersion to avoid engine temperature to mess things up. Judging by the video, I suspect there is no possibility to get two capillary tubes mixed up?

1719599769726.png
 
GMPolara said:
I've put about five six once cans in.
Click to expand...
Way too much.

I'm not an A/C authority so I can't give you much help, but I do know that over-charging with 134a is not going to help. There's some formulas for pressure, but I think most just measure output temperature and charge until it's blowing real cold. Too much and the output temperature starts warming up.

IIRC, it takes about 2 1/2 cans for me to fill my A/C with 134a.
 
My 71 2bbl 383, with AC switched to 134 blows cold, and no overheating problems with engine, even in drive in an hour long traffic jam. I do have original shroud, original fixed fan w/o clutch.
 
Late to the party. What is the systems total capacity? Five 6oz cans is only 30oz, not even 2lbs. Most of these older systems took 4lbs. When we first started doing A/C conversions from R-12 to R-134A, 80% was the rule of thumb as a starting point. I have used up to 100% in some systems. I always use a gauge set to see the pressures so I know what is going on, but I have the advantage of access.
 
Ross Wooldridge said:
Cool (no pun intended) - good to hear.

Was it just slipping and not turning the compressor much? How did you diagnose it?
Click to expand...
It was the fan clutch. Not locking up so it would cool properly.
 
Ross Wooldridge said:
Right- just wondering how one figures that out...
Click to expand...
I think the OP's was loose. THe clutches usually leak. THey should have some resistance when cold and pretty much free wheel when warmed up. When the thermostat spring get's hot, they will lock up.
 
You must log in or register to reply here.

Similar threads

GMPolara
68 Polara 383 Heads
Replies
19
Views
1K
GOLDMYN
G
E
1968 Dodge Monaco - 383 2bbl - exhaust manifold leak
Replies
9
Views
747
Just Carbs
J
surfnturf
Which AC compressor. RV2 or Sandon on my 66 New Yorker
2
Replies
36
Views
4K
66 Fury III Convertible
66 Fury III Convertible
HappyJack
Stalls when warm. Electrical?
Replies
17
Views
1K
d366
D
M
Center A/C dash vents blow both heat and A/C
Replies
4
Views
802
Mark Pifer
M
Back
Top