96 Roadmaster no A/C

You should know what this is. If not, you probably roll your windows down a lot.
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Re: 96 Roadmaster no A/C

Post by kevm14 » Tue Aug 20, 2019 3:01 pm

Borrowed all the A/C stuff from Ed so I will do the fan stuff and then vacuum/charge the A/C. Or perhaps start vacuuming while I am doing the fans. That might be smart.

Posts: 14077
Joined: Wed Oct 23, 2013 10:28 pm

Re: 96 Roadmaster no A/C

Post by kevm14 » Wed Aug 21, 2019 7:51 am

This is good to know. Important sections highlighted.
The following is a Four Seasons "Tech Tip" from http://www.4s.com

Hope this helps someone. I use the 30# can with scale method

"Charging with Cans, Guess Again?

Unlike the old days when an R12 system could be +/-½ pound on either side of full and still produce cold air, an R134a system is not as forgiving. The acceptable operating window for R134a cooling is about +/- 2oz of full. This is why technicians should recover and recharge to O.E. specifications rather than attempt to œtop-off a system that is being serviced for a low charge. The charging method you choose will make a difference in the accuracy of the final charge amount. For greater accuracy a charging station or a 30lb cylinder and an electronic scale is the preferred method of charging. The charging accuracy is questionable with the use of 12oz cans. One problem with can charging is a misunderstanding as to what is meant by 1 pound of refrigerant. Many technicians today still speak of 1 pound cans, which have not been produced since the late 1960'™s. The industry also saw the use of 14 ounce refrigerant cans until the mid-1980'™s. Today when we speak of 1 pound of refrigerant that amount is equal to 16 ounces. When we speak of 1 can of refrigerant that is an amount that is equal 12 ounces.

When recharging with a charging station or with a 30lb cylinder and an electronic scale, you need to add 2oz to the system capacity specification. This extra amount is necessary to compensate for the amount of refrigerant retained by the equipment or manifold gauge service hoses, whether you are vapor or liquid charging. So, if the vehicle calls for 28oz you will need to program in 30oz to ensure a full charge into the vehicle's A/C system. NOTE: Some charging equipment requires you to add 2oz to the total charge amount, while others designs add the amount automatically. You will need to be familiar with how your equipment works. If in doubt read the equipment documentation or contact the manufacturer.

If the method of charging R134a is with 12oz cans, then you have to compensate for the amount of refrigerant to an even greater extent. You will still need to allow 2oz for the service hoses and since you can never completely empty a can of refrigerant you will need to allow for an additional 1oz per can. This occurs because the can's pressure and the vehicle's A/C system low side pressure equalizes, this stops the transfer of refrigerant. So, if the vehicle specifies 30oz, you would require the use of three cans. This would be 36ozs, less 2ozs for the hoses and 1oz per can times 3. That would put you within the operating window at 31oz. True, the final charge is 1oz over the required specification, but it is as close as you can guess with the use of small cans.

The drawback to using 12oz cans is when the specification calls for an amount requiring less than a whole can. Example: a system capacity of 24oz. You may believe 2 cans would give you a full charge, but actually only places about 20oz into the system. A 3rd can is then required to finish charging the system but you can only guess at the 4oz needed. You could easily over charge the system. You will also have an undetermined amount left in the can, leaving you to guess again at the charge on the next vehicle being serviced.

The amount of refrigerant retained in a 12oz can is dependent on the temperature of the refrigerant in the can. Whereas the amount of refrigerant retained in the service hoses is dependent on the length of the hoses and temperature of the refrigerant. The above examples are consistent with the refrigerant at room temperature around 85°F. When the component temperature is below 70°F, the amount retained could be twice as much.Heating the refrigerant with warm water (maximum 115°F) will increase the pressure of the refrigerant in the can and reduce the amount retained in the can to about ½oz."

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Joined: Wed Oct 23, 2013 10:28 pm

Re: 96 Roadmaster no A/C

Post by kevm14 » Sun Aug 25, 2019 6:58 am

Wasn't as good with taking pictures along the way but I have a lot of them from specific parts of the job.

I accomplished basically two main things:
1) Installed primary electric fan and wire harness kit to power and control it (integrated with factory stuff)
2) Vacuumed and charged the A/C

Before I started, I took Ed's idea and put a little refrigerant into the system and sniffed for leaks with the detector. The only thing I really found was the low side service port. I was going to replace the valve cores (probably good practice when doing a major service like this) but then it seemed to stop leaking, or never was and just had a little R134a pooled inside the port.

Once that was good, I connected the vacuum pump. It took me a while to figure that out. First I connected the wrong end of the suction hose to the manifold so nothing was happening. Once I figured that out it began to draw a vacuum. I left that running for however many hours it was while I worked on the fan and harness.

The fan job was a little slow. Even just installing my Caprice's old primary fan took a while because I needed some hardware. I could not find another coarse thread bolt for the top so I ended up switching to an M6 U-nut from Ace and a new M6x1.0 bolt. Then for the radiator end tank bolt, I determined the factory U-nut was also M6x1.0 so I just got a 12mm long bolt and used a large washer I had. This sounds quick but took a while between running to the store and fooling around with sizes and stuff.

Once the fan was physically bolted on I began the wiring project. In summary:
- Gary does a very nice job on the harness but aspects are a little tricky or tedious. Finicky. That kind of thing.
- Most of the work happens at the relay/fuse box which is on the rear passenger side area of the engine bay. You basically pull it out, remove the comb retainers and remove some pins, add others, install a jumper, etc.
- Run the fan harness to the fans and plug them in
- Connect a ground
- Run the primary signal wire over to the PCM, remove the "RED" plug, open back shell, push new pin in #11 slot. Remove air filter box to get to this but otherwise quite accessible.
- Put the fuse/relay box back together which took a few tries considering the wiring underneath, and also install fuses/relays as necessary (including a new 40A fuse and new relay for the primary fan)

I don't think I even tested anything. I think I proceeded directly to the A/C stuff, figuring it should work.

New fan next to existing secondary.
Nice deep vacuum.
New A/C compressor.
Turn off low and high valves on manifold. Disconnect suction line from pump, install on A/C tank. Close high side valve at manifold but leave open at car to monitor high side while charging. Open A/C tank and press valve a few times at manifold to purge air. Put the tank on a scale and tare it to zero. Car takes 28 oz but given what I found I wanted to do 30 oz (or 1 lb 14 oz).
Open low side at manifold and let 'er charge. It takes a while especially doing vapor only and when the can is low.
Low side is showing about 40 psi while charging and high side around 185 psi. By the way the primary fan came on when the compressor began to cycle. Also, the compressor began to cycle!! The older style does make a very audible CLICK when engaging. Disengaging is silent.
Here we are at almost a full pound out of the container.
Primary fan running, which means my Caprice's old fan still works and all my wiring stuff worked.
At 1 lb 12 oz, a couple things happened. First, it kind of stopped charging because the tank pressure had dropped so much (it was cold at the bottom). Second, the scale shut off. It seemed to have a timer regardless of me pressing the units button periodically. The target was another 2 oz to account for refrigerant trapped in all of the lines and manifold but I decided to let the tank warm up for 20 minutes. I shut the valve and let everything rest.
Also I revved the engine a little to run the high side up to 250 or whatever and the secondary fan kicked in as designed to pull that down. So that all worked, too. Yay.
After letting the tank warm up, I was able to add 2 more ounces with no issue. I didn't measure vent temps because it felt cold and the correct charge is the correct charge.

In the car, I did notice that the temp gauge climbs up pretty high before the primary fan turns on. I expected this though I was surprised just how high it goes up. Usually gauges don't show you this kind of information but there is quite a bit of sensitivity here. On a modern car I bet at 225F you wouldn't even see the gauge budge but this one swings over almost to the red.

So here we are at the primary fan turn on point. It is 225 or 226F in the calibration (I forget). But this is how high the needle will normally go when idling (without the A/C on, which turns a fan on and this is prevented).
The fan turns off at an indicated 217F which, again shockingly, is a very noticeable gauge swing.
And then the engine settles another degree (which you can actually see in the gauge) before starting to warm back up again. It doesn't quite fall to halfway.
In operation with the mechanical fan, or when moving at some speed like 35 mph or more, you won't see the needle go much above the 1/4 mark. So the good news is nothing is overheating and is working as designed. I still find these temps too warm and would like to program them cooler as I have done in my previous LT1s. But this is a 96 which means software will need to be purchased.

I believe GM rated the V08 mechanical fan cars at 250hp with the rest being 260. So I guess this was worth about 10 hp. And increased serviceability of basically EVERYTHING at the front of the engine.

Thankfully the car is back on the road and I can call on Monday for an inspection appointment next Saturday (last day of August).

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