Bobcat

Replaced leaking heater core and A/C evaporator coil, fixin' to put the heater box back in the truck. Replaced the accumulator as well, on advice from a friend, and the expansion orifice at the condenser outlet.

Book says 7.75 oz PAG oil for the whole system; says the evaporator holds 2 oz, and accumulator 4 oz. I did not get that much oil out of those parts and don't know how much to add - 6 oz or what?

Also don't know where to add it - pour into accumulator and evaporator before closing up and evacuating? Or get the oil in the little can pressurized with R134A and add it to the low side when charging the system?

I did try the "search" function, got all sorts of good stuff to read, read it, and still don't know what to do about the oil. Any help or guidance will be greatly appreciated.

Regards,
Andrew

Silver R/T

R134a cans will already have oil in it mixed with refrigerant. That's why when you're recharging system you tilt it up and down (from 12 to 3 o'clock) position so that oil will pour into the system.

torquefan

I've never been afraid to add an ounce or two of extra oil to a system. It seems that some of them are a bit short on oil from the factory. As far as where to add it to the system, I keep in mind that the closer it is to the compressor's inlet, the better the chance of the compressor getting a gulp of liquid and hydrolocking.

Busboy

I just took a look in the 2000 factory book to confirm the total system is 6.2 floz. Now I'm pretty sure the lines and the evaporator core are the same on the diesel truck from 1995- at least 2001 so is the accumulator. so why the difference???
Are you using a factory manual? The 2000 says 2 for the evap and 2 for the accum. You may not have got that much out of the evap and accum but there is some still left coating the insides. You can add the oil where you want as it will distribute itself throughout the system when the AC is running. Too much oil is NOT better and will give poor cooling, just add the correct amount. You can buy the oil in bottle form but you either have to pour it into the system or use an oil injector and inject it into the suction side of the system. If the system has not been charged yet you could disconnect a suction line and pour it in, 4 floz is not much.
You must vacuum the system before charging. After you shut the vacuum pump off leave the gauges on and see if the vacuum drops, you should have 29-30 inches and it should hold it, if not you DO have a leak.

Bobcat

Thank you.

Factory manual, and the computer at the autoparts store says the same - 7.75 ounces.

I just got the dashboard back in, the A/C is still not assembled. I'm going to flush the condenser and replace the accumulator. New evaporator coil is still capped, nothing is hooked back up yet. Lines from pump are taped off. Sounds like I could just add 4-6 ounces of oil to the accumulator before I install it and hook it up - you think?

I understand about the vacuum, and looking to see it holds.

This is so weird - my brother and I grew up in the 50' and '60s, working on all kinds of cars and bikes. We never learned about A/C - considered it a power-robbing add-on - but in Texas it is necessary, not a luxury. So I'm an old dog (cat) learning new tricks... better late than never, I suppose. Still, only so much you can learn from reading, I have to learn by doing - and come across certain questions that only someone who knows something about it would answer.

Anyway, thanks to everyone who answered. Back to work tomorrow, wife's car, the truck will have to wait a couple days. But the heater box is back in, the dash is back in, all that is left is assembling, evacuating, and charging the A/C.

Regards,
Andrew

Busboy

Like I said the oil will distribute itself throughout the system once running so if you don't have an oil injector then just open a convenient part of the suction side and add it. I notice you intend to flush the condenser so you will need to add oil for this, my book calls for 1 floz for the condenser does yours have a listing for the condenser? If not maybe that's the difference.

Bobcat

Yes, the condenser says 1 oz.

You see, you already taught me something new. I did not know there was a tool called an oil injector. Got to look it up now, even though it seems like adding to the accumulator is the way to go.

Thanks again.

Regards,
Andrew

Busboy

The top of the oil injector hooks to the center of the gauge manifold then the freon tank hooks to the bottom of the injector. The injector has a removable plug to fill with oil (mine holds 2 floz) then uses the freon to carry the oil into the system. It's good for adding oil after changing a component or fixing a leak. If yours has a cable driven blend door someone must have changed it over, Check to ensure that the outer cable is anchored at both ends as it sounds like that is the problem. If one end becomes detached then the inner cable doesn't travel the whole distance so the blend door won't seal. this would allow cool air to bypass around the heater core. The same thing would happen if there was a kink in the inner cable.

Bobcat

Busboy,

The blend air door works and the cable is stock. I've had the truck since new in 1995 - 453,000 miles and counting.

The foam and stuff on the various doors inside the box is pretty shot, but I was too lazy to find new foam and totally rebuild it all like new. The cable moves the door and I can feel it (and before putting the dash back, see it move).

The evaporator core was corroded on the outside and (get ready to laugh!) covered with shredded paper napkins - mice had been living in there! The fan was full of shredded paper too. Not much throughput.
When the heater core started leaking, misting the windshield so I couldn't see out, I bypassed the heater core with a loop of heater hose so I could get to work. It does not get cold here, but it was about freezing or 35º F for a few days, so the ride to and from work was unpleasant.

My plan is to put fluorescent dye and about 4-6 oz of PAG oil in the accumulator, just before hooking it to the evaporator coil; last thing to go in the system. Then pump it down. I think the only risk is if it does not hold vacuum and I have to open it, the PAG oil will absorb moisture if I don't seal the accumulator up good. Is that right?

Thanks again, this has been a real learning experience. Good for an old man to learn new stuff, keeps the mind young.

Regards,
Andrew

1-2-3

General rule from a guy I know that's done ac work for 40 years is one ounce of oil per component replaced, unless it's the compressor, then pour all the old oil out of the old compressor and measure that. Dump all the oil out of the new compressor and replace with the same amount that came out of the old compressor. He's never had a system fail yet using that so that's what I did and mine have never failed.

Busboy

Oops I have been posting on another thread with HVAC problems where the truck in question is a 1998 and I mixed the two of you up, sorry. I think the blend door changed to electric after 1995. One thing though with our trucks I think that putting dye into the system is a waste of time and money. IF the evaporator is leaking you will pick up the leak with a leak detector long before you see the dye, a front compressor seal leak will show oily and a condenser leak from a rock will be very evident, those three are the key places for leaks.

Bobcat

Yeah, I read that thread and figured you were helping both of us sort our problems out.

I put dye in it, put about 5 oz of PAG 100 oil in the accumulator, put it all together and pumped it down. It held vacuum for 35-40 minutes so I filled it - two cans, 24 oz, the book says two pounds which would be just over 2-1/2 cans, but I've read that the 134A systems work best a little low and did not want to have an open can on the shelf.

It cools, it heats (defroster works!) and I'm very happy to have it back on the road, and to have gotten rid of a mystery. Learning is good; frightening to open something I know little about, but once I've been through it once it is ok.

Thanks for the factual advice and the figurative coaching.

We'll see tomorrow if it held the charge.

Regards,
Andrew