A/c completely dead, need advice

Take it to a reputable shop, or buy a service manual. Might want to spend the $15 on a service manual first anyway so you can check the simpler stuff yourself. Either way, if the system needs evac and recharge you're going to need to bring it to a shop for that due to freon regulations.

I recently repaired the A/C on my truck. I took it to a shop for diagnosis which revealed leaking compressor seals. I couldn't justify the cost to replace with new for a 9yr old truck so I had them leave the system empty. I then replaced the compressor, orifice tube and accumulator dryer myself using inexpensive rebuilt parts. Once I was done I brought the truck back to the shop for evac and recharge.

The A/C is now working fine and I saved quite a bit of money. Of course you can't expect the shop to warranty anything other than their refrigerant charge, but considering the money saved I could do all the same again and still be ahead.

Pete C.

Most likely due to an empty system. The low pressure switch is preventing the clutch from engaging.

To diagnose, find the LPS on the accumulator and jumper the connection while the a/c is on. If the clutch kicks in, that is the problem. Don't run it for long. Just verify the clutch kicks in. If the clutch does not engage, you have other problems. Get a manual and a DVM and start tracing.

With an old R-12 system, it will probably not be cost effective to get it fixed and charged with R-12.

What I would recommend, providing you have the tools, is to convert to R-134.

First you need to figure out where the R-12 leaked out. Most likely on the high pressure(hot side) of the compressor. Probably the crimp right next to the compressor.

Replace whatever is leaking. Replace all of the o-rings in the system. Replace the orifice tube. Replace the accumulator.

Drain all of the oil you can out of the hoses/system.

You can get little adapter ports to change the R-12 ports to R-134. Get those and screw onto your existing ports.

Fill the system with the recommended amount of PAG oil(it will say on the compressor).

Seal the sytem up. Evacuate the system(requires a vacuum pump).

Charge with 80% of the recommended charge for R-12 with R-134a.

Enjoy the cold.

Suggest that you take the car to a dealer and have them fix the car.

The system has plenty of refrigerant. I would have expected that the at least the condenser fan and boosted idle to kick in if it was just low on refrigerant.

I tried jumping the clutch relay and the compressor engages. the system actually cools extremely well.

I figured it would be low refrigerant when I first saw the car too, but I pushed on the low-side schrader and got a huge blast coming out.

thanks for the advice.

Would have been helpful to include that information in the original post, we aren't mind readers. At any rate if you've traced the problem that far it would seem the problem is the clutch relay, one of the pressure switches the wiring from the pressure switches or the switch on the dash. A factory wiring diagram would be a big help in isolating it.

Depending on the vehicle you may be able to replace some of the pressure switches without having to evacuate and recharge the system, but you'll need the manual to tell you that. If not you'll need to take it somewhere to have them recover the refrigerant so you can change the switch and then have them put the refrigerant back if you find the switch is at fault.

Pete C.

Is there some reason you didn't include this in the first message? The first message reads like someone who knows nothing about cars.

Masospaghetti wrote:

I just wanted to know what could cause the system to be _completely_ dead, because usually the fans at least turn on. I tried posting about a week ago with a hugely long description and didn't get a single response.

i've gone through and tested the following components, which tested OK:

low pressure switch a/c thermostat a/c delay timer a/c relay clutch relay a/c clutch a/c diode radiator fan relay a/c switch

none of the relays are even getting a signal. is there some control box that the button goes to that might be bad?

Thanks

-James

John S. wrote:

In at least some vehicles the A/C command from the dash switch routes through the ECM and then to the A/C compressor clutch relay. This allows the ECM to disengage the A/C clutch momentarily during hard acceleration / high engine load to recover the HP used by the A/C compressor and give better performance.

You could have a failed connection in wiring to / from the ECM, or you could potentially have a blown output on the ECM which could be and ECM failure itself, or be caused by a short circuit further downstream that could kill another ECM output if the ECM is replaced without resolving the real problem.

Again a factory wiring diagram or at least a look at one to collect the relevant information would be a big help here.

Pete C.

I've done this myself before, however I have a leak detector, vacuum pump and guage set, flush gun and can do everything without paying a shop. Keep in mind that if you get 2 years out of an inexpensive rebuilt compressor, your doing pretty good.

Ted

Do you also have a refrigerant recovery / recycling unit and EPA cert. for refrigerant? I can't justify the time / money / effort for those given the couple times a decade I might use them. Easier to have the shop recover, I do the work on the empty system and then have them evac and recharge.

Pete C.

Well, since I'm not cutting into the system unless it's not working, and when it's not working almost always it's a result of a leak, I'm generally not dealing with existing refrigerant in the lines. Typical reason compressors blow and I've seen it many times before in used cars I've bought, is the crimped fittings on the flexible hoses to the compressor start to leak, then the owner gets the little chargette cans and starts filling up the system every summer, meantime the oil level in the system gets lower and lower then bang - compressor seizes one day, and then they give up refilling it. By the time the vehicle comes into my claws the A/C system has sat open to atmosphere for years.

Fortunately I do NOT own a vehicle where you have to disconnect the A/C lines to remove a minor item.

As for evacing and recharging, my observation was that back when I had shops doing that, they would hook up the vacuum pump for perhaps 5 minutes, then call it boiled out. In other words I don't trust them to do it right. When I evac my car A/C system, I put it under vacuum with the pump running for at least an hour, then I let it sit overnight under vacuum. Then I charge immediately into the vacuum system.

You don't need an EPA cert to purchase R134a, you can get it for $8 a can at Walmart.

Now, I'll get on my soapbox here.

As for evacing the manifold guage when you disconnect it from the A/C system after you finish servicing it, which you are supposed to do, I used to feel guilty about just venting the guage hoses to atmosphere. Then I learned that all asthma inhalers in the country use R134a as propellant, as do the hand held "air" horns, the "air duster" in a can that computer techs use to blow the dust out of your PC, and it is also used as a foaming agent for insulation. (to make the little bubbles in it) Outgassing of R134a from insulation alone literally dwarfs by an giant order of magnitude, service releases of R134a from A/C service work every year, even if every A/C tech in the country didn't bother to evac the service hoses. I also really cannot bring myself to believe the EPA scare stories that R134a might be hazardous to human health when the medical community is venting throusands of tons of the stuff directly into the lungs of asthma suffers every year.

If you investigate the issue you will find that one reason R134a is so expensive now is that every year theres NEW uses for it that are non-refrigerant, that are being developed, most that involve eventual venting of the stuff to atmosphere. The people getting all worked up about using compressed CO2 in A/C systems in cars (as some of the misguided European nations are mandating) really have rocks in their heads, it is a gigantic, huge political thing tied up into global warming that has really no bearing on actual use.

The EPA takes the position that everything has to be recovered in A/C work, and I think it is a good postion, but not because I think R134a is harmful. It is because profesional refrigerant techs deal with a lot of nasty A/C refrigerants all the time other than R134a, such as R12, R22, ammonia, etc. and from a bureaucratic standpoint it's just easier to make one rule for everything, and ignore reality.

But the reality is that the EPA has been looking for something definitive to use to nail R134a to the wall as damaging to the atmosphere and to life and they have been unable to find anything. That is why they are not able to ban the sale of 14 oz R134a cans in auto parts stores and such, even though they would absolutely love to do so. So, in my opinion, the EPA mandate for reclamation and recycling of R134a is nothing more than pure political posturing, and is being done for the benefit of the Save-the-Whales crowd who mostly are too stupid to come in out of the rain.

End soapbox

Ted