When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
But, I've run into a specific issue as I work through the A/C repair that seemed like it warranted a separate thread.
I think my primary question in this thread is:
Why are the inlet and outlet lines to the evaporator hot?
My A/C doesn’t work.
I have attached a 10-minute video at the bottom of this post. I realize that some of you may not have access to bandwidth to watch videos, so I’ve tried to write it out. I’ll include just a couple pics so you can see the manifold gauges.
High side (about 400 psi) and low side (about 40 PSI) lines are hot at all times.
At one point, the high side went extremely high (450+) – so high that it caused refrigerant, oil, and dye to spew from around the connection of the red hose and the manifold gauge.
Is that a sure-sign the compressor needs to be replaced?
Why is there any pressure in the system if the compressor is failed?
Is there just a blockage somewhere in the system?
Is there too much refrigerant in the system?
Is there too much oil in the system?
Is there too much dye in the system?
I would very much appreciate any advice you all might have as to what to do next.
Here are the facts:
· 1988 Camaro, 2.8 V6
· A/C system was converted to R134 by a prior owner.
· I hired a pro shop to recharge the A/C a few years ago. Car is driven infrequently – really just enough to keep fluids circulated every couple weeks.
· A few weeks ago, I took it out for a drive to the BBQ joint on a 90-degree day. When I got back in the car after lunch, I decided to give the A/C a try. I immediately noticed a large vapor cloud coming from under the hood. I opened the hood, and I saw vapor cloud and oil coming from around the shaft of the A/C compressor. I immediately shut off the A/C.
· I went home and ordered an A/C kit, consisting of a compressor, dryer, and orifice tube.
· I also acquired a vacuum pump, and a set of A/C manifold gauges, and a pancake air compressor.
· Poverty is not a problem with this project. I’m not wealthy, but I’m pretty sure my bank will cover the tools and parts to get this fixed.
· I have a pretty good supply of general mechanic tools, and I can buy other tools as may be needed.
· My work-space is my level driveway by my house. Today’s weather forecast was for clear and hot weather. The only tool I was lacking was the tap-valve for the R134 cans, and that valve is supposed to arrive later today.
· I have no prior experience servicing automotive A/C. I did receive two years auto-repair training as part of my curriculum in high school. In the 1970’s.
· I did some reading and watched some videos on automotive A/C.
· It appearing today that I had the time, tools, and parts to do the job, I carried everything out to the driveway to start the job.
· First step was to test static pressure in the system. I expected there to be NO PRESSURE in the system because of the incident at the BBQ joint a few weeks ago where there was the vapor cloud and oil spewing from around the compressor shaft.
· To my great surprise, there was significant static pressure in the system. Before starting car, both gauges (high side and low side) were each reading about 100 psi.
· I decided to start the car to see how the pressures changed while the compressor ran.
· As the motor ran, and with the compressor activated, the high side would climb as high as 400. Low sided would drop to around 40.
· Ambient temperature for the test was mid-80’s and high humidity.
· The car seems to have a second issue, in that the blower doesn’t seem to blow any air through the A/C ducts.
· The blower itself turns (I can hear it), and it does blow (rather weakly) through the defrost ducts.
· Both lines to/from the evaporator are very hot to the touch at all times while the compressor is operating. There is no sign of any condensation on any of the evaporator lines, or the dryer.
· At one point the high side pressure shot up really high. Probably 450 or more. I was in the cabin, trying to measure the temperature of the vents, when I noticed a large vapor cloud under the hood. Refrigerant, oil, and dye were spewing from around the connection between the red hose and the high side of the manifold gauge. I shut the connector-valve to the red hose, and waited for the spewing to subside. I checked the connection between the red hose, and the manifold. I could not detect any looseness. I had been running the motor and gauges without incident for several minutes before the spewing incident. I removed the red hose from the manifold gauge, and inspected the connectors. No sign of anything amiss. I re-connected the red hose, and ran the car and gauges some more without further incident. I will admit that I was in a bit of a panic when I was trying to make the spewing stop. But, I did glance quickly at the high gauge before taking action to shut-down the spew. The high gauge was reading very high – probably 450 or more. I’m thinking the pressure shot up so high while I was fiddling around in the cabin, that the previously adequate connection between the red hose and the manifold gauge was pressed beyond its limits to hold. What would have caused the pressure to go that high?
Start with the concept of "vapor pressure"... if you imagine taking some liquid and putting it in a 5-gallon bucket of vacuum, filling it only part of the way, covering it up and sealing it, and watching the pressure, eventually it will stabilize. The pressure will reach a value that's totally independent of how much of the fluid you put in the bucket, as long as there's still some of it left a liquid. You could put acoupla ounces, a gallon, 4.9 gallons, ... won't matter. The pressure will go to the same value regardless. If you raise or lower the temp, it will go up or down accordingly.
That's the situation inside your AC when the compressor isn't running. The refrigerant has an inherent vapor pressure at any given temperature, largely independent of how much refrigerant is in the system. (apart from hard vacuum for example) For R-12 or R-134A it's somewhere in the 80 - 120 psi range at typical US summertime ambient temperatures. Both sides of the system will reach that pressure and just kinda sit there. So that's your first photo... 95 psi or thereabouts, perfectly normal. If the engine is hot, the pressure will be correspondingly higher; might go over 120, but still, normal.
With the compressor running, things change. Its job is to take refrigerant from the low-pressure side and put it into the high-pressure side. Ideally the refrig stays a gas on both sides: the act of sucking it out of the low side will lower the temp on that side a bit, but it will raise the temp on the high side ALOT. Then it flows to the condenser, in which its temp is lowered. Lowering the temp is another way of saying that it gives up heat... specifically, its heat passes into the air the main cooling fan is pulling through the condenser. The cooled gas condenses into a liquid.
From there it passes through the orifice tube. That is located in the high-side line, just past a fitting, just before the evap. it's just exactly what it sounds like... an orifice. It regulates the amount of refrig flowing through there; without that, no pressure would ever be able to build up in the high side.
The fluid evaporates in the evaporator. (surprise!!) Like any fluid that evaporates, the act of doing so, requires heat. By doing so, it absorbs that heat from its surroundings. (pour some gasoline on your hand and blow on it, and experience directly the phenomenon of evaporation extracting heat from its surroundings) We call the condition of being able to absorb heat, "cold". Air from either the outside world (recirc, aka Max Air in these cars) or not (every other setting) passes over the evap and gives up its heat to the refrig, becoming cooler in the process, and is blown into the cabin.
The gas that is probably still somewhat cool passes out of the evap and into the suction line, and the process repeats. Heat is allowed to pass from the cabin air into the refrig in the evap, then the compressor raises its temp by compressing it, (imagine that... all of these parts have names that actually MAKE SENSE!! Not everything is like that) the condenser "cools" the gas or more accurately transfers the heat that used to be in the cabin out into the wide wonderful world, the gas condenses to a liquid, passes through the orifice tube, where its temp is lowered by the state change from liquid to gas, and the process repeats.
Think of the whole system not as something that "generates cold", but rather, a conveyor belt for heat. Its job is to manipulate the gas/liquid state of the refrig in such a way as to allow moving heat from one place (the cabin) and putting into a place that's at a higher temp than the cabin (the outside world). Literally, like making water flow uphill, except instead of water, it makes heat flow uphill. Almost seems to be a violation of the First Law of Thermodynamics, except that work and state-change are involved.
Note that one of the most important things about this is, that the cabin heat must eventually be carried away by the air that the engine fan pulls through the condenser. So, requirement #1 for a good-working AC system is, a good-working engine cooling system. (or at least, the fan part of it)
Your AC pressures look pretty much OK, except that the high side is WAAAAAAYYYYY high. I'd be expecting to see something around 275 - 300 lbs in an ambient of, say, 90°. 3 things could cause that: a blockage in the system, overcharging, or poor engine fan cooling.
A blockage isn't all that common, but is by no means "impossible". However, if the system was "blocked", odds are, the low side pressure would be VERY low, maybe even lower than atmospheric (partial vacuum). It's not. So I think that can safely be ruled out.
Overcharging is also not uncommon. However when that occurs, the low side pressure will ALSO tend to be WAAAAAAYYYY high along with the high side pressure, because the refrig won't be able to evaporate. But it's not. Your low side pressure is right where it should be. That also can safely be ruled out.
This leaves option #3. I never heard an engine fan AT ALL in your video. I believe I'd start there. You have a 6-cyl, and I have not the vaguest dimmest remotest foggiest hint of a whiff of a glimpse of a clue what the fan system is on those. Never even seen one. Might be mechanical (belt & clutch), might be electrical, might even be hydraulic for all I know. So I can't help you there, except to tell you that it should be ... doing ... something.
The compressor is fornicated. The sound alone tells that. But it seems to still be producing pressure, much as a car with wore-out rod bearings can still run OK.
That fixed, next thing to look at is the underside of the evap housing, where it faces the exh manifold. You'll have to lay on the ground and look up, maybe with one of those REAL POWERFUL beam flashlights. EVERY ONE of these I have EVER seen that was more than about 10 yrs old (I'm gonna guess that's gonna include yours), the housing had COMPLETELY crumbled TO DUST under there. Bad choice of materials on the part of the factory I guess. (like SO MUCH else in this system) When I looked at my own some years back, I found that it had a hole about 3" x 5"... there was almost NONE of that whole side of the evap housing LEFT AT ALL. I could just look up in there and see almost the whole evaporator. I pulled the housing out and repaired it with fiberglass, and voilà! my blower actually began to produce detectable airflow into the cabin.
Anyway, go take a look at those 3 things - main cooling fan, stoooopid connector, and evap housing - fix what you find wrong, and let's see where that takes you. You'll need a compressor and all the rest FOR SURE, but let's get the infrastructure squared away so that when you work on the AC, it has a prayer of working, because it won't be crippled or disabled by all these other things before it even has a chance.
Last edited by sofakingdom; 08-15-2018 at 06:49 PM.
I did just check the main fan, to see if it was coming on when the AC controls were turned to MAX.
Nothing happening at the main fan. Its stationary.
The only time I've ever seen my main fan come on is when the coolant temp reaches a fairly high temp.
I'm going to try to get under the dash and see what is the condition of the evap housing tomorrow.
The dash is already partially disassembled. So, I've got a leg up on that at least.
Thanks for confirming that the sound tells all about the compressor. I was pretty sure it was toast just from the sound of it, but I'm not really experienced enough to say for certain just based on sound.
Would a blocked orifice tube cause the odd situation with the pressures (low is normal(ish), but high is crazy high?
That yellow Slurpee that was blowing out around the manifold gauge connector was disturbing. Rather not see that again.
The main fan HAS TO be on when the AC is on, or the AC will not be able to transfer any heat from anywhere to the outside world. Find out why it's not coming on when the AC is on and fix it. That might cure the situation where the entire AC system is hot. In fact that might be why the compressor died in the first place: it's supposed to be cooled by the refrigerant flowing through it, and if the refrig is never cooled by the main fan, ... the compressor is going to get TOASTED. The heat in the system has nowhere to go.
I don't think the OT is blocked but don't worry about that just yet. You're already replacing it so it's moot. Look at the main cooling fan, the high speed battery feed, and the evap housing, first. You can have the best compressor ever made, the perfect amount of refrig down to the last molecule, the correct OT choice, ... and if those other things aren't right, your system, and YOU, are STILL efffed.
Incidentally, the evap housing is in the engine compartment. The blower is on top of it. The housing is brown. The part that crumbles and disappears is facing the pass side exhaust manifold. It's REAL hard to see when the engine is in the car. The entire housing comes out with about 7 bolts. They're relatively large, some 10mm and some 13mm heads if memory serves. About 3 or 4 of em are accessible from the engine side, and the other 3 or 4 are in the interior, just under the top edge of the carpet. If you take them all out the whole thing - evap, blower, housing, and all - just lifts right out. In fact I think that might be how it was put in at the factory: the WHOLE WHOLE WHOLE system will lift right out if you do it right. Compressor, lines, condenser, harness, evap housing, ALL as a giant unit, without even disconnecting the lines. I'm pretty sure that the systems came from Harrison to the vehicle assy plants (Norwood & Van Nuys) fully assembled and pre-charged, and the assy plant production line people just dropped em in, before they put in the radiator.
I will I’ll dig into the primary-engine-fan-not-coming-on as first thing to solve.
Let me throw one more question:
This is about the BLOWER switch on the panel in the cabin.
The blower switch rotates, and has four click-stops.
Am I correct that the click-stop that comes AFTER the highest speed is the OFF position?
So, starting at the 12 o’clock **** position, the blower speed goes low, then medium, then high, then OFF.
This may seem like a simplistic question.
But, every other vehicle I’ve been familiar with has the OFF position adjacent to the LOW blower setting. Is it correct that my Camaro blower switch, properly has the OFF blower position adjacent to the HIGH blower-speed setting?
Nowhere on the control panel for the blower switch is there any marking (a dot, or any sort of lettering) to signify an OFF position.
.
.
.
The full-counter-clockwise step is Low(est), and the full-clockwise step is High. The fan operates in all 4 positions. (when working right, which yours isn't)
There are 3 resistors in the resistor assy. The first 3 steps of the fan speed switch, feed battery from the brown wire under the dash, to progressively lesser resistances. The resistors are in series with the motor, which is how they control the motor speed. Power goes from those to the Normally Closed contact of the high speed relay (the one that connects to the Common contact when the relay is not energized). A relay is an electrically operated switch, which allows a small amount of power to be fed to the coil that can then control a much larger amount of power, in this case the blower motor.
The Common contact is connected to the purple wire that feeds the blower. The 4th step, High, feeds battery to the relay coil, operating it. This causes its Common contact to move, disconnecting from the Normally Closed contact, and instead connecting to the Normally Open. When that happens, hard battery from the big fat red wire you may have read about somewhere, which is intended to be connected to the Normally Open contact, replaces the feed from the resistors as the supply to the Common contact, applying full battery voltage to the blower. It does this so that the very high blower current in High speed doesn't have to flow through the ign sw, dash wiring, fan sw, and all that.
The reason your High speed doesn't work is covered in the 3 links up there.
Last edited by sofakingdom; 08-16-2018 at 07:39 AM.
08-15-2018, 02:30 PM
