A/C woes

[codyPKA]

A/C stopped blowing cold air recently. Thinking my freon had probably run out I purchased a refill kit. Problem is, the compressor stopped turning has at all (when the problem first started, it would turn on and off and on and off). This is not allowing me to get a reading of the freon level. I don't want to make a mistake an accidentally overfill the freon, cause I heard this can cause quite a bit of damage.

By google-ing the issue it seems like some people recommend "jumping" the low pressure relay with a paper clip, which should get the compressor turning again. Should I try this? and if so, how exactly is this done? If anyone has pictures or a write up on this I would be a happy camper if you could link them

 

[SVTContique]

Clutch pack in the compressor gone?

 

[STAMPEDE3]

Quick cycle as it was doing is a sign of low refrigerent.

The pressure switch is on the drier by the firewall.

Unplug it and simply use a wire or paperclip to jump the switch. it is really simple.

However if the system is close to empty the can should start going in and the compressor should start kicking on eventually.

 

[Oceanside78]

Mine did this as well. I just kept filling it and then boom, the compressor kicked on. BUT, it kicks on and off every few seconds. I would fill while on, stop when off. Somethings bad on mine, because I read full on the gauge when the compressor kicks on, but it will still cycle back and forth. It blows cold consistently though, so I haven't fixed it. But I can tell when it kicks on and off when driving because it almost feels like a slight misfire when it kicks back on. Not noticeable under accel, but when cruising I feel it.

 

[ESVEETEE]

The pressure switch is designed for the low pressure side, and when you are low on freon, the low side will dip below a certain threshold, at which point the compressor will kick out.

If your freon gets low enough, it will never be above this threshold, and the compressor will remain off. It is okay to add a little (maybe up to half a can) to see if the compressor will kick on.

Think about it like this... Your compressor is a big pump. In order to pressurize the high side, it has to pull a vacuum on the low side (sucking in more freon to keep the pressure up). This is why if your compressor is not running, you may see that you are overcharging your system, when in fact you aren't.

Your gauge is intended to read the pressure on the low side with the compressor engaged.

Jumping the pressure switch isn't the greatest idea. If your compressor is that low on freon, it is likely low on oil as well. Get some refrigerant that has compressor oil in it.

 

[DSG2003Mach1]

IF there is freon in the system you should have pressure weather the compressor is running or not. To me it sounds like you have a leak and its bled out to the point that the low pressure switch is preventing it from coming on (to protect the compressor) and not even registering on the gauge.

when initially charging the system it will look like you are over charging as you finally hit the cut on point for the compressor it will cycle and if you had a manifold set youd see the high side pressures bump up every time this happens...kinda hard to diagnose ac stuff with only the low side pressure

 

[codyPKA]

just tried adding the can of freon. I used what feels like almost the whole can. It seemed to be taking the freon, but at no point did the compressor come on. the gauge read as being empty when the trigger was released and read way over in the red section when the trigger was pulled.

While I was out there I checked all my fuses and they are all fine.

Not sure what else to try at this point. Should I try jumping the switch? If so, how is this done?

 

[codyPKA]

figured out how to jump the switch. Did it, and POW! Cold air! The system wanted a little more freon in order to top it off.

So this means I just need to get a new switch like this?
Santech/A/C Switch (MT0444) | 1996 Ford Mustang Cobra 8 Cylinders V 4.6L SFI | AutoZone.com

 

[codyPKA]

or is it this part? Buy Factory Air Air Conditioning Harness Connector 37235 at Advance Auto Parts

 

[KCRN12]

Mine did this as well. I just kept filling it and then boom, the compressor kicked on. BUT, it kicks on and off every few seconds. I would fill while on, stop when off. Somethings bad on mine, because I read full on the gauge when the compressor kicks on, but it will still cycle back and forth. It blows cold consistently though, so I haven't fixed it. But I can tell when it kicks on and off when driving because it almost feels like a slight misfire when it kicks back on. Not noticeable under accel, but when cruising I feel it.

Compressor cycling is normal. If it stayed on constantly you'd freeze the evaporator. And yes, it does put a huge load on the engine. Most compressors in cars as old as ours drain about 30hp from the engine while they're running.

figured out how to jump the switch. Did it, and POW! Cold air! The system wanted a little more freon in order to top it off.

So this means I just need to get a new switch like this?
Santech/A/C Switch (MT0444) | 1996 Ford Mustang Cobra 8 Cylinders V 4.6L SFI | AutoZone.com

You still might want to put some dye in it and check for leaks. When I charged mine after the engine job it took forever to get it full, so if it was pulling it in easily, it probably was pretty low. And just because it started running again doesn't mean it's at the right level. Did you check the capacity before you bought the refrigerant?

 

[Oceanside78]

^cycling every 2-3 seconds like clock work??? Only car I've ever seen do that....

 

[Oceanside78]

just tried adding the can of freon. I used what feels like almost the whole can. It seemed to be taking the freon, but at no point did the compressor come on. the gauge read as being empty when the trigger was released and read way over in the red section when the trigger was pulled.

While I was out there I checked all my fuses and they are all fine.

Not sure what else to try at this point. Should I try jumping the switch? If so, how is this done?

I had to add 2 cans before mine kicked on

 

[laddanator]

Issues

I am having some issues as well. I have a 96 Cobra and A/C stopped working so I replaced every seal I could get to (including the seals on the compressor) and the freon lasted 4 days. So I checked the low side service port and could see freon bubbling out around the black rubber inside of the port so I replaced the service port, pulled vacuum on it the system for 9 hours and held pressure for two hours so added more freon. Well today I went out to check it and the compressor is kicking on and off every 2 seconds but air seems to be cool. At this point instead of tracking down a leak if it is a leak, I am ready to replace the whole system. Do you guys know where I can buy a complete A/C system that comes with everything? Or like Oceanside78 car is this compressor cutting on and off every 2 seconds the norm?

 

[STAMPEDE3]

It should not cycle that fast/much.

Try Tousley if you want OEM or compare them to aftermarket.
If not go to NAPA

http://www.svtperformance.com/forums/sn95-cobras-24/322845-oem-ford-parts-10-over-cost.html

Tousley Ford: Full line Ford, Lincoln, Mercury and Ford Racing Distributors. - SVTPerformance

 

[Oceanside78]

So why does it cycle that fast but still blow cool?

 

[codyPKA]

i replaced the pressure switch this afternoon and all is well! Once again, SVTP comes through big time. freon charge kit- $35 and a new switch- $12. A hell of a lot better than taking in to a shop. Thanks everyone

 

[95PGTTech]

The system is not filled with "freon", problem 1.
Problem 2, is you should have given us high and low side pressures with the clutch off and on (in your case, not on) for us to have any information to help you diagnose.

You got lucky, guessed, used Google, and again, got extremely lucky. I am glad that your end result was a working A/C and not a hole in the compressor. Diagnosing > guessing.

 

[Oceanside78]

i replaced the pressure switch this afternoon and all is well! Once again, SVTP comes through big time. freon charge kit- $35 and a new switch- $12. A hell of a lot better than taking in to a shop. Thanks everyone

Where'd you get the switch? Easy to install?

 

[codyPKA]

Where'd you get the switch? Easy to install?

my local autozone had it in stock. Easy as pie. Disconnect the harness, then the switch simply unscrews. Screw the new one on and reconnect the harness. So easy even I can do it :dancenana:

 

[Oceanside78]

That's the switch back by the firewall correct? What exactly did you ask for from them?