AC Charging

[tnporsche]

Ok charging a system ac comp not kicking in from low freon. Could bypass low p switch and make comp kick in. R134a

And this is on my dads pickup a 1997 chevy v6. Sorry putting this in the 944 forum but no other forum I have found is as cool as his one.

Started with 30 psi low side 80 psi high side

After small amount into charging comp kicks in. good right?

Ended after 1 can 134a with 85 low and 150 high only slightly cooling in cab

Temp chart says after taking reading should be 215 psi high side

Only thing thats strange is the low side climbs so fast to a point I feel I should stop, but the high side's way off from what the temp chart says.

Does the 85 low press reading suggest a problem in the system? Should I ignore the low side and continue to 215 if it would?

Thanks

[mattdavis11]

These compressors are notorious for failure, but it's usually the case seal. Your dad's sounds as if it's disintegrating internally. The tell all will be a black oily substance on the compressor if it's a case seal.

There is a chance you upset the orifice tube when charging, if that is the case, let it sit. You should have taken a look at the orifice tube when it was evacuated, replacing it would be even better.

I hope you have a vacuum pump because oil, R134A and oxygen create and acid which will destroy an ac system.

The system requires 8 oz of pag 150, and 2lbs of R134a.

Let me know if you need parts or help.

Edit: Did you charge as a liquid or a gas? Can was which way? Upside down? Charge on the low side, always, in your case, it's on the accumulator.

[tnporsche]

Upside down, and yes on low side.

I have a vac pump but I did not pull it down because it seemed to have some freon, just low.

Someone told me if there is at least 50 or more psi diff from low to high then comp is working. Agree?

I am thinking something is wrong because of the high low side press.

[mattdavis11]

The low should be around 32-38 with a properly working compressor at full charge. The high side should be between 175-225 depending on the ambient temp and how well the fan clutch draws air. The condenser may be dirty and air flow is low if the clutch is good. Your low side tells me the compressor might be toast, or the freon isn't being cooled in the condenser.

The orifice tube tells you everything. I'd replace it anyway.

Most people wouldn't do as I, but I grab a blade on the fan and have someone fire it up to show them the fan clutch is toast. It's probably original equipment and the reason the compressor is shot.

[tnporsche]

I will have to research were it is located on that veh. Im gona guess in the line.

It has a compressor just like he 944. The high and low lines bolt on together,

there is a small orange juice can size section in each line near the comp. Is the the orifice is in that line, in one of those can sized things? Then that means replacing both lines.

Were is it on the 944?

Thanks

[mattdavis11]

The 944 is an expansion valve car, and it's near the evaporator. The mufflers are what you describe. You dad's orifice tube is in the high side line right at the fire wall, pull it out with needle nose pliers. The high side line is the thin one, the fat one is the suction or low side returning oil and refrigerant to the compressor.

Be careful, those fittings can be frozen. Sometimes this requires heat, penetrating oil, and patience. Two wrenches, one a 23 and the other a 20, I think, Two large crescent wrenches will suffice, work it back and forth, don't let the evaporator side of the line move, loosening the drier will help, removing it may be necessary, along with some electrical components mounted on the firewall.

[tnporsche]

Thanks alot, I will try that.

That sounds great that sounds like the line can be saved.

Is the orifice clean-able or just replace?

[mattdavis11]

Orifice tubes are cheap, maybe $5. That won't solve the problem if it has metal shavings on it though. If so, the compressor is done. You have to do the complete job, flushing and all.

[wild man]

[QUOTE=mattdavis11;5366453]one a 23 and the other a 20[QUOTE]

Huh? I've never seen those sizes. Unless you mean 22 and 19, it's probably more like 15/16" and 13/16".

[mattdavis11]

It might be 22 and 19. When you see as many as I do, you forget from make to make. You're right, standard will work too.

[kuehl]

Originally Posted by tnporsche

Upside down, and yes on low side.

Its preferred NOT to charge upside down (liquid) through the low side as it can liquid 'slug' the compressor and damage the reed valves. Does not happen often but it can.

You can charge liquid through the high side (engine off always) and gas through the low side (engine running or off).

If you are charging by gas (can up right) and you want to speed up the process, place the can in a small bucket of warm to hot water to raise its internal pressure.

[tnporsche]

Ok, thanks.

I had another one I was working on yesterday. A potiac grand am it had 30 low and same high. comp not running. Charged to 38 low and 198 high. Results very much like the other one I charged. Pressure looks good but does not cool.

If pressures are like above, does it mean there is no blockage? What else could cause no cool but pressure looks good?

[mattdavis11]

Gm has issues with their climate control units. I actually reset one today for an ole boy on the road. Had no clue who he was, but when he said that he had battery trouble, I knew exactly what was going on.

Depending on the year of the grand am, it maybe that simple. The guy I helped was blowing cool on one side and hot on the other. 2 minute fix, just pull the hvac power fuse. Sometimes you have to turn to full hot then cut it back down.

[kuehl]

Originally Posted by tnporsche

Ok, thanks.

it had 30 low and same high. comp not running. Charged to 38 low and 198 high. Results very much like the other one I charged. Pressure looks good but does not cool.

If pressures are like above, does it mean there is no blockage? What else could cause no cool but pressure looks good?

Sometimes you can have a good vacuum, normal pressures but things are not happening where they are suppose to (in the evaporator), such as from excessive moisture in the system or a contaminant that causes the expansion to take place before the expansion valve. Run the system again and inspect: a) the evaporator core temp, it should be cold like between 28f and 40f if the TEV is working, if its cold you have other issues between the evaporator air outlet and the vents, b) inspect the inlet hose to the expansion valve, if it is not hot but rather just warm or cool then you know your problem is down stream before the valve, such as at the drier for example.

[mattdavis11]

Wrong, he's working with an orifice tube car. I hope you replaced it. The orifice tube is in the high side line, the accumulator/drier is after the evaporator.

I'm thinking blend doors where the evaporator is fighting the heater core.

[kuehl]

Originally Posted by mattdavis11

Wrong, he's working with an orifice tube car. I hope you replaced it. The orifice tube is in the high side line, the accumulator/drier is after the evaporator.

I'm thinking blend doors where the evaporator is fighting the heater core.

Oh, your right Matt, I keep thinking this was a Porsche.
Yeah, you can totally forget about expansion happening before the orifice.
No inline aftermarket filter before it right?

[mattdavis11]

I don't think there is anyway he'd know the answer to that question. I won't use them and hope no one else ever does. The orifice tube does the same job and then some.

The service valves are very important, especially the high side on GM vehicle such as your dad's. They leak. They should be replaced every time the system is evacuated.

We are looking an HT6 and probably a v5 or v7. I need more info on the grand am.

[tnporsche]

He got a new tube and we are going to try again this weekend

[kuehl]

Originally Posted by mattdavis11

I don't think there is anyway he'd know the answer to that question. I won't use them and hope no one else ever does. The orifice tube does the same job and then some.

That is interesting Matt. I guess someone could explain to him what it looks like, where to find it in the system, you know, just in case... by the way, what is your experience, problem wise, with 'in line filters'... other than they can trap the trash before the orifice tube . Can they get clogged just like an orifice tube and prevent oil from flowing through the compressor or is there some benefit in using them, in your opinion.

[mattdavis11]

Originally Posted by kuehl

That is interesting Matt. I guess someone could explain to him what it looks like, where to find it in the system, you know, just in case... by the way, what is your experience, problem wise, with 'in line filters'... other than they can trap the trash before the orifice tube . Can they get clogged just like an orifice tube and prevent oil from flowing through the compressor or is there some benefit in using them, in your opinion.

No benefit in the long run can I see. The filter you describe is always in the high side or liquid line, the thin line. Maybe it's in the manifold line right at the back of the compressor, but it could be at the union after the condenser or before the orifice tube. To be honest, I don't know exactly where on the high side it is in this grand am, but it gets blown out while I flush and I'm the least bit concerned when it does. That little filter sold GM lots of compressors.

The micro filtering devices do exactly what you'd expect, they choke flow. When little to no oil returns to the compressor, heat is inevitable and the compressor sends shards of metal down the line, that's why they blow up.

Ordinarily, no trash gets by the orifice tube anyway, but the condenser gets loaded up with debris when chunks of metal get shot down the line if a compressor lets loose. That's no big deal. Flush it, unless it's parallel flow or micro tube, then replace it.

The orifice tube does a great job alone, you don't need other filters. If an accumulator lets loose then I'd choose a filtering device that mounts between the compressor and the hose assembly (that is not micro), but I flush lines, so there is really no need.

Expansion valve cars are the way to go, undoubtedly. However there are variable orifice tubes depending on climate.

I'd really like to know what compressor I'm dealing with on this Grand Am. R4? V5? V7? HD 6?

What's the year?