I tried searching and couldn't find this so here goes:

On a 2003 4.7 Durango with Rear A/C, do I need to have the rear ac turned on while charging the system, or do I just run the front only and use those pressures?

 

Let me clarify more and see if anyone knows, I charged my system using front only to 30psi on low side at 80 degrees, but when I turn on the rear ac my pressure jumps up to 40psi, is this normal? I see nothing in the factory manual about pressures with the rear ac on.

Btw this is a "new" charge, I had to replace the drier due to a faulty gasket leak, I vacuumed the system down and it held -28 for a couple hours, I then charged the system using 1oz of Pag oil and 36oz of 134a.

 

Well, let me start by answering your first question.....

As long as your compressor is running you should be okay but, to be safe i would have the full system on.

Second, you don't wanna worry to much about pressure at first. At 80F the MAX PSI should be 30 PSI after its been charged and settles, not what you charge it too.

The first concern is to get the correct amount of refrigerant into the system. With that being said, a dual system calls for a total on 30 OZ (1.88 LBS) of refrigerant. If you put 36oz of 134a and 1oz of oil in the system then you have a total of 37oz in there.. that means your system is 7 oz overcharged.

The correct way to fill a system is to add the correct amount of refrigerant and oil. Then after the system has ran and the refrigerant has a chance to "settle" then you check the pressure. It should be between the allowences for the outside temp. I your case at 80F your pressure should be between 20-30 PSI on the low side after the system is charged and settled.

 

Ahh ok, I will have to let some go then. I did not know you had to also add the oz of pag oil to the oz's of 134a.

Thanks for the reply.

 

If i where you i would get the whole system empty. The i would stop by Autozone, there the sell 14oz cans of 134a that have the oil, stop leak, and a red dye (incase you get a leak) all in one can. That way you don't to worry about anything but adding 2-14oz cans... For the other 2oz you could add a can of chiller booster for something to get it to the correct oz's

 

I used the pag oil with UV dye in case I have a leak. From everything I have read the stop leak 134a's didn't work, they just clogged up the recover machines?

 

FYI......When you charge you should have both systems running full blast.

Also, unless you've lost oil from somewhere in the system you should not be putting extra in, you should only buy strait coolant.

Yes, stop leak plugs up the system.

 

Got busy and just now getting back to this, you had me worried I over filled my system but you must be quoting from a different system, mine takes 2.44 lbs.

I added the 1 oz because I lost some due to a bad gasket at my drier.

 

Yeah the 98-00 Dual systems only take 30oz (1.88 LBS)