I got my AC re-charged and converted to r-134 but it still is sparatic <----the compressor keeps switching on/off and tugs on the engine, very annoying). There's no leak for the coolant to leak out so that's not an issue.

Anyway the shop said it's 1 of 2 things ( the ac controller switch itself is bad, or it's the wiring to the compressor) and this is how they will determineit:

1) replace actual ac unit switch for $150 + labor. I'm guessing that is GM pricing. I'm trying to see if I can find a lower price on used or a friend's GM parts discount.

Now it could still be faulty wiring to the comressor and I could simply throw away that money, plus this:

2) They could "hot-wire" from the ac control switch to the compressor to see if it's either wiring or the switch for $150. If it's the wiring then it's a simple fix job and no more money spent, but if it's not, then I have to go with both and it will be over $350.

What should I do?

Go with #2? Eventhough it sounds kinda ghetto, but it does make sense. But I don't want to spend another $230 on top of the $150 Hot-wire job in case it doesn't work.

Anyone have any suggestions? Should I go to another shop or bring it to a GM shop? I know they are expensive, but they usually do the job right and have GM parts on hand.

Thanks.

 

Ac keeps cutting on/off, tugging on engine...just got recharged with no leaks, but problem persists. Shop guy told me it could be the actual switch unit ($150+labor to install).

However, what could possibly be wrong with the AC switch? Do these things go out frequently? What could I look for? Would I be able to fix it myself, or at least replace it?

I remember there being all sorts of thick metal "bands" that are connected to the levers and such and I don't remember seing anywhere to disconnect them.

Can anyone point me in the right direction?

Thanks!

 

Check to make sure the low pressure switch in the accumulator is working. A good way to test it is to cut the engine and AC on, if the compressor is not cycling, tap on the low pressure switch and see if the compressor will cut on. If it is cold out side the compressor will cycle faster, so you may have no problems at all.

 

Check the pressure sensor, tap on it with the ac on and car running, see if it comes on. This is a normal problem for them.

Also you can "hot-wire" it yourself to see if it is, at the canister senson, unplug the connector and connect a wire between the two prongs, again with engine running and ac on, if the compressor comes on and stays on, its the sensor. If it pops on and off then its the wiring.

I am going to guess its the pressure sensor on the canister line. Check this first.

 

I'm sorry I'm confused with what you wrote. So turn the engine off with the ac in the on position?

Where is this switch at? Are you talking about the AC control "Low setting"?

 

If you have a pic I can refer to that would be great. Where is the pressure sensor and how do I tap on it? And where is the canister sensor?

GTA MATT referred to that pressure switch as well.

 

If you gave us the year of your car it would be helpfull.

There's two locations, one on the accumulator or one on the very back of the compresser. The one on the accumulator has a cycle duity adjustment and a simple adjustment may be needed.

 

Thank you SSC, I forgot the one on the compressor.

The two sensors are easy to locate and we can give exact locations per year of vehicle.

The pressure sensor is on the Accumulator Canister line, this is thr big silver canister on the left hand side of the motor beside the heater core area to the left of the wheel well. The sensor is the only round piece about 3"x2" screwed into the lines with two wires comming off it. This one is where I would start. Please post your vehicle information and we shall continue assistance.

 

If the compressor is cycling, the compressor and clutch are obviously functioning. The wiring to the clutch is also probably just fine.

I'd suspect the low pressure switch on the accumulator as well. If the system was charged properly, and ambient temperature is below 70°F, the system will cycle as a normal function of refrigerant pressure fluctuations.

On the other hand, if the ambient temperature is 95°F or higher, and the system was converted to R134A, you may have a high pressure problem.

I'd also be somewhat suspicious of the shop's work. Study the repair invioce. If the information is not present, ask exactly how many pound and ounces of refrigerant was added, how many ounces and what type of refrigerant oil was added, whether the expansion control was re-sized for R134A, and if there was a new filter/drier installed as part of the conversion (which is always a good standard practice).

 

BTW - In case you see some duplication, the two threads on this topic have been merged.

 

Here's a link to a forum that I found very helpful last summer when I was working on the AC in my Lumina. A lot of people that post on this forum are in the trade and own their own shops. Very helpful group. You might want to post your question there.

http://www.autoacforum.com/

I know that an R12-to-R134 conversion is a bit more involved than just adding compatible oil and filling up with R134.

 

I have a '91 Lb9 Trans Am if that makes a difference.

Thanks guys.

 

I see the diagram and I found the high and low ports, but how do I "check" them?

They both have black plastic, screw on caps. I removed those and put my finger on it with the car & AC on and nothing happened. I did that to both.

What next?

 

Hello?

Well last night the ac was ice cold, today it's hot!!

What the hell?!!! The AC guy told me there was a leak and it could take 2 days or 2 years to be empty. I did it anyway because the price of the conversion was less than the price of freon.

I did a little recharge kit and that made the accumulator cold, but it still didn't make the AC cold, it was still hot!!

I will not buy $1000 ac system for a car that needs paint, turn signals, and horns first.

AAaaaarrrgggggHHHHHHH!!!!

 

The repairs should not be that expensive. Chances are you have a hose, hose connection, or fitting leaking. If the repair shop did a good job, they should have been able to isolate the leak. If the leak is very small, they should at least have injected some UV dye into the system to make leak tracking easier in the future. If they did, you should now have a very apparent trail of dye when viewede with a UV lamp.

Instead of a marginally effeciive R134A conversion, they should have sold you R414B. If they did such a poor job of diagnosis, they likely did a poor job of converting the system. That would actually be good, since the original orifice tubes are better sized for R414B, so all you need to do is find and repair the leak, evacuate the system, and recharge with oil and refrigerant (NOT R134A this time).

 

Mine does this as well, and it's because I have a slow leak which causes the pressure to get too low for the compressor. I replaced the condenser and some lines, but it still did it. Well over $300 later I still don't have AC, and I don't have the heart to just tear it all out.

 

So Vader, just go to a different shop, tell them the history so far and what the other shop might've goofed on, and request R414B, correct?

Thankyou sir!