need MORE AC help...

[DavidT]

1. I added a 12 oz. can of freon a couple weeks ago. The $10 gauge read 38 oz. after filling it. I checked it today. Now it reads like 46 oz. If I rev it in idle, the needle on the gauge will lower as I rev it... the more I rev it the lower it goes. Reving to about 3-4K rpms, the needle would drop to about 25 oz. As soon as I let off the throttle, the needle would climb right back to 46 oz. The compressor runs the whole time.
Have I overfilled the system? Is the needle on the gauge responding properly...(Is this normal?)

2.I have disconnected my battery twice in the last couple of days. After reconnecting it, and driving my car, EACH time, the AC would take like 5 minutes before blowing cold air. This only happens after disconnecting and reconnecting the battery. Whats the deal? Is this related to question #1?
Thanks in advance...

 

[Glue Maker]

Have you checked the AC clutch? I deshimmed mine and it works all the time now

 

[ricky]

The A/C should have between 25-45 PSI on the low pressure side with outside temps in the 60-90 F range. The $10 gauge sounds like it is reading PSI as ounces. It is normal for low pressure to drop as engine revs go up. When you disconnected the battery, the computer had to "relearn" other operating parameters and took longer to kick in the A/C.To maximize A/C performance put in a fresh cabin filter and clean the gunk that may have built up between the A/C condensor and radiator. beware, not an easy place to clean.

 

[DavidT]

thanks guys

 

[DavidT]

thanks guys

 

[DavidT]

The A/C should have between 25-45 PSI on the low pressure side with outside temps in the 60-90 F range. The $10 gauge sounds like it is reading PSI as ounces. It is normal for low pressure to drop as engine revs go up. When you disconnected the battery, the computer had to "relearn" other operating parameters and took longer to kick in the A/C.To maximize A/C performance put in a fresh cabin filter and clean the gunk that may have built up between the A/C condensor and radiator. beware, not an easy place to clean.

So, if I am 6 oz. low on freon, do I add freon until the gauge reads 6 psi more?

 

[Mr Anonymous]

So, if I am 6 oz. low on freon, do I add freon until the gauge reads 6 psi more?

You want to add enough refrigerant to get the gauge to the top of the "normal" (should be the blue range on an ID gauge), with the compressor running (clutch engaged).

When the compressor is not running, the gauge will go way into the red, which is completely normal. It's the compressor running pressure that needs to be measured.

 

[DavidT]

So, the question of ALL questions is.......
how in the heck did the stealership know that my system was 6-8 oz. low on freon???? How do they come up with that number by reading psi gauges? Whats even more confusing to me is that our car's "normal" reading should be 22-45 psi... boy, that is a HUGE variance.

 

[Mr Anonymous]

With a set of REAL A/C manifold gauges, you can more accurately measure the low and high side pressures, and thus determine the amount of refrigerant in the system making those pressures, and add or remove refrigerant accordingly.

This isn't rocket science, I think you're probably trying to over-think this. Using the el cheapo gauge, fill it to the top of the "full" indication on the gauge while the compressor is running. If the compressor won't run continuously, you can disconnect the pressure cycling switch from the top of the accumulator and short the two pins in the harness connector together to force the A/C clutch to stay engaged.

If after verifying the refrigerant is charged to the proper level, if the compressor still short-cycles or you can visually see the clutch slipping, then you'll probably need to address the clutch, possibly by changing to a thinner shim. If the compressor clutch is working properly, but your A/C is still not working properly, then you'll probably be looking at a blockage.

 

[DavidT]

Well, I am wanting to make sure that my 1 year old compressor is maintained properly, which I would imagine would be hard to do if there is a leak in the system.
I was VERY close to shelling out $100 for a nice set of manifold gauges... but what research I did, I learned that the manifold gauges will help you diagnose the entire A/C system. I am ONLY interested in knowing if I have the RIGHT amount of (oil and) refrigerant in my system. From what I gathered, the low side gauge is all that is needed for that.
Everything seems to be working fine for now. I have decided against the manifold gauges for now.
Basically, I am trying to figure out how to determine the EXACT amount of freon is in my system... knowing that 34 oz. is FULL. Also, with my leak... I am concerned about the amount of oil in there too.

 

[Mr Anonymous]

Well, you can do it a few ways. Easiest is to evacuate all the refrigerant from the system and then add 34 oz. back in. The oil is generally heavy enough that most stays in the compressor, evaporator and accumulator and you would only need to add about 1/2 oz. oil to top it off; or an even simpler way is just to buy refrigerant with the oil already in it at the proper proportion.

When we do motor swaps, the A/C system is opened up and all the refrigerant escapes. We drain the compressor of oil while it's out of the car, and after everything is back together and the motor is running, we add 8 oz. of PAG oil and 36 oz. of refrigerant (three 12 oz. cans is just easier, and puts it right at 45 psi on our version of the el-cheapo gauge which is nearly identical to the Wal-Mart version with the addition of a trigger grip for dispensing).

If you're really that concerned about the quantity of refrigerant and oil in your system (it's not as exact a science as Ford would have you think -- for instance I run about 7 oz. of oil and 40 oz. of refrigerant in mine), pay a shop to evacuate and vacuum your A/C system, and refill it with 8 oz. of oil and 34 oz. of refrigerant. If you think you have a leak, buy a can of flourescent dye and put it in there first, and they can use their black light to check for/identify leaks before doing anything else.