My A/C hasn't been too good over the last few days - it's over 40C here, I need it - so I took the car to an A/C shop.
To my horror the guy pointed to a bodge job the previous owner must have done and told me the 'bulbo' was missing. Now 'bulbo' in Spanish means something like a round-shaped device, typically a sensor. But what sensor? The dealers don't have the item anywhere in town and so the guy ordered it, cost is $80. But WTF IS IT?
The item in question: If you lift the hood, there is a fuse box with a black cover just behind the right side of the radiator. Between that box and the rad, three wires exit the harness and a connector is dangling there. Some stupid arsehole has bodged some bits of wire and insulation tape onto it, but I assume there should actually be some type of sensor or control mechanism.
Can someone who has a proper working item please enlighten me as to what it is and what it does? Thanks.

 

Thats going to be the pressure sensor solenoid. Sounds like the previous owner tried to jump it to bypass either low or high pressure. How has your AC worked in the past?

 

The AC has been working fine; I had to have the expansion valve and dryer replaced about 5000 miles ago, but since then it's been great. I had no idea that part was missing.
Yeah, I know what the pressure sensor is. Stops the compressor from running in the event that there's insufficient Freon. Stupid to bypass it... guy must have been a retard. Thanks. It'll be fixed ASAP. Main thing I hate about used cars is the crappy bodge jobs that retards do to them. I gotta drive to McAllen next weekend and I am for sure not doing that without an AC.

 

Gahhh... $140 so far. $80 for the sensor, just a tiny thing like a bolt with a wire sticking out the top. Other $60 for labour and Freon.
It worked great . . . for about 4 hours. Then later I tested it and the AC was useless. Back to the shop today....

 

I have had a similiar problem! My A/C slowly stopped working and then died. The mechanic said that the compressor is not compressing. The clutch kicks in and everything though? He told me it was going to cost $800-$1000!

 

If the compressor is actually running with the clutch engaged and Freon in the system, you can hear the distinctive sound of it when you turn the AC on or off. Kind of makes a noise a bit like a Chevy valvetrain.
But if there is really no Freon in the system then the LP sensor (on the can below the black fusebox behind the rad) will not allow the comp clutch to engage. (If you run the comp without Freon it will be destroyed, probably seize, due to lack of lubricant)
The AC guys tell me the Max compressor has rather delicate 'reed' valves that can easily be damaged, e.g. by suddenly discharging the system to atmosphere. They can be replaced. However if it really is the compressor you should be able to pick up a good used one for not more than $300.

 

I'm planning on buying a new compressor from eBay. I had a friend look at it and he overfilled the freon and it clicked off then he let some out (most of it) and it shut off again. We filled it correctly and it would only cool to about 70 degrees at night. I took it in and had the mechanic evacuate and refill the freon and now it doesn't work at all. The clutch kicks it and the compressor spins but is not cooling whatsoever. When I get in my car after work it is about 155 degrees in my car. Not a good time for the A/C to quit working. The mechanic also said the the control unit is not sending a signal to the compressor but I think they are crazy. It turns on the A/C! Just doesn't get cold.

 

Let's see if we can get a bit more diagnostic here.
1. Is the coolant low pressure pipe getting cold? If it's not getting cold then either there's no Freon or no compression or no expansion.
2. You already mentioned you overfilled it and were still only getting 70F min. That's no good. So we can eliminate 'no Freon' from the equation.
3. That leaves, either bad compressor or bad expansion valve.
Of the two possibilities the compressor is the more likely.

 

Well, my own problem continues. The LP pipe gets cold. However the outlet air temp is too high. Maybe 70. It should be 50. And it cycles between cooling and not cooling.
The AC shop doesn't seem to think there is a lack of Freon in the system.
I disagree, so I'm going to take it somewhere else.

 

I replaced the compressor and the expansion valve. Fairly easy. Now I just have to take it to get charged. I had problems finding the right parts. Part stores didn't even list parts for the A/C system. I had to go to Advance Auto to get correct compressor but they gave me the wrong filter/drier and couldn't figure out why it was the wrong one. And btw, no the coolant pipe was not getting cold. As far as your problem goes, I'm clueless. Have you had them evacuate and refill to get the junk and moisture out?

 

Yeah... mine will have to wait till I get back from the UK in three weeks time.
I just can't figure out what is wrong. System is full of Freon. Both cooling fans turn on when I turn on the AC. The pipe gets pretty cold, but the air coming out the vents is only a little cooler than ambient. And pushing the recirc button has no effect. Actually I tried every combination on the auto climate control, leg vents, face vents, both, defog, whatever. No difference.
I did notice one strange thing. I don't know if it is related. When I turn the ignition OFF, I feel a draught of cool air on my feet, as if a vent opened down there. WTF? I don't recall that previously.
The AC guy seems to think it's an electrical problem. I'm wondering if the compressor is failing; maybe it is compressing, but not enough. I notice that I can't really hear the compressor any more, and I have a feeling that I used to be able to hear it clacking away when it was on.
Anyone have these symptoms before?

 

If you have automatic climate control, then from what you describe sounds like an air management issue within the HVAC unit in the car. One of the directional doors might not be functioning correctly, allowing air to pass over the heater core. Thats why your A/C low side is indeed cold, yet the system doesn't blow cold air.

 

You've got to be right. Makes sense. The pipe is cold. I can't really hear the compressor like I used to. And it's not blowing cold. I deduce that the compressor is quiet because it's not running most of the time, because the cold matrix isn't getting airflow. Which means you must be correct, it's an air management problem. Oh no... well I guess there are three possibilities: a bad wire or connector, a broken door actuator or something jammed in the door ... oh crap I think I know what it might be: some stupid little kid filled the intake vent area with stones, it was impossible to get them all. I bet that's what has jammed the system. I'll have to check.

 

AC repairs are always going to be expensive. Almost every issue with AC will result in you having to evap and recharge your system. At work i haven't see any real AC job except for the simple recharging of it cost less then 4 hours in total. There are only like 10 items or less in your AC system.

 

cool sleuthing njmaxseltd!

 

So my next question has to be:
How difficult is it going to be to dismantle the HVAC system to the point where I can clean out all the grit and whatever that's fouling it up?

 

Your problem sounds exactly like mine with one exception: my pipe wasn't getting cold. Anyone need the A/C pressure switch that goes on the filter/drier? The stealership is the only place I could get the filter/drier and it comes with a pressure switch. Stupid little filter (and switch) cost me $111.

 

actually you can run a hermetic compessor just fine with no refrigerant in it(freon is no longer in use as it kills ozone and people.. new name basically lol)
theres an oil in the compressor that keeps it lubed up. so even if you has a leak and all your gas escaped you could still turn the compressor on, run it, but nothing will happen.

as for your A/C problem... ive got the same sort of thing.. it BARELY gets cool, and if the outside temp is high it just blows hot air. if the outside temp is like 72*f then it does a decent job of giving me cool air. so basically when i need it, its totally useless, when its cold enough to not need AC, it works great. *sigh* and i dont have $350 for the stealership to do a diagnostic on it and fix it....

 

ouch... probably could have bought your own from an A/C supply store for about $3.. thats what i use in my phase change coolers, they work fine.