When I put the heater defrost A/C control on the defrost or mix setting there is a clicking noise coming from under the hood. There also seems to be a slight loss of power. When I opened the hood to see where the noise was coming from it seems to be at the rear of the alternator. There is no such noise in the heat setting. The defroster works fine other than the annoying noise. My wife tells me, (it is really her van),that this problem occured after she bought a new battery but I am not sure about that. Any ideas? You guys are great.

 

this might, stress might, be your A/C cycling on and off. if you're absolutely sure it's the alternator then disregard this.

 

Year? Engine? AWD? Tranny? Rear Heat?

Some more info would be nice.

 

Sorry I always put that info. 91 aerostar, 3L, automatic, 2 wheel drive, no rear heat that I know about. It still seems the sound, clicking, is coming from the rear of the alternator. When it clicks the engine seems to lose power.

 

When I put the setting on A/C it does the same thing. I read in another post where the guy was hearing a buzzing sound on the defrost setting and someone replied that it was the clutch in his A/C. Does anyone have info on what is involved with fixing that? if that might be the problem.

 

If you have rear controls for heat-a/c, then you have rear air.

But I think that xzume has it nailed, your clutch is sticking or your compressor bearings are starting to go. Your compressor is run whenever you turn on the defroster. Just to double check, go ahead on turn on the A/C and see if it makes the same noise. The compressor is located below the alternator so you might be misconstruing the sounds comming from the alternator.

 

Well then you have just found your problem. It would be easier and cheaper just to replace the whole compressor. Ready-Aire rmfd Compressor w/ clutch runs $169.99 at CSK where a new clutch runs $102.88. At that age the bearings are usually going in the compressor anyway, and instead of doing the work twice, just get it over with once.

 

However hearing the clutch click while running the A/C is completely normal this is simply the vehicle turning the A/C on and off to let the condensor cool down, preventing freezing of the evaporator coils, or if the van is running at WOT it disconnects the clutch to prevent compressor damage.

 

So whats involved with changing the compressor? Could a person somehow disconnect the A/C for the winter and would the defrost then work again without the compressor problem or are do they work somehow together or on the same system? I have a good source for very cheap used parts which I may try first but does removing and replacing the compressor get into opening up the A/C unit and having to have it recharged? I like going with the used parts because I have to do the work of removing the parts myself and it gives me practise of how to remove and replace my own before I actually attempt it on my own vehicle even if I later end up buying the parts new. The noise when the A/C is put on is not the same as usual as the clicking is occuring every few seconds.

 

The system has to be evacuated and the refrigerant recovered. It is a serious crime (25,000 USD ?) in most if not all jurisdictions to just let the refrigerant escape into the atmosphere by depressing the Schrader valve on the accumulator, although I suspect most DIYers do just that. On the 3.0, R & R of the compressor is difficult due to its location - much more difficult than R & R of the alternator or starter. Then the system has to be vacuumed and recharged. Unless your system has been converted to R134a you have R12 in it. It takes somewhere between 2.5 to 3 lbs of refrigerant at about 30 USD per lb for R12 and about 10 USD per lb for R134a. These are the two main refrigerants but there are other replacement refrigerants of varying utility and legality. Most new replacement compressors will work with R12 or R134a, but if the rest of your A/C system is original you might not get such good cooling with R134a without replacing other components.


Absolutely. Just pull out the electrical plug on top of the accumulator.


I wouldn't use a junkyard compressor because it may cause the Black Death - bits of compressor coating the inside of your system, gumming everything up - especially if its been laying around for a while.

When you have the defrost on I think the air goes through the evaporator first then the heater core. If the warm air from inside the van is then recirculated it could result in less compressor cycling. As krankshaft says, it may be normal. The compressor might just be wearing out and getting noisier, in which case the Black Death is in your future. It happened to me.

Jan Richter

 

You can certainly pull the wire off the a/c clutch to keep the compressor from running in winter defrost but this happens automatically, the cycling pressure switch will eliminate the compressor running below about 40 degrees F period.

I was in alaska last winter and needed more heat from my heater. I put the a/c control in Max a/c position (recirculatin cabin air) it was cold enough to prevent a/c from engaging but heat output rose substantially because 10degree outside air wasn't being used. this really works, you guys in north country muight give this a try on a frigid cold night..

Ken

 

Printerguy:

The A/C compressor will engage in all settings except Vent and Flr. When you turn on the defrost, the compressor engages to cool down the air before it goes through the heater core and is vented to your windshield. This is done so that moisture in the air will condense on the evaporator first, giving you dry air at the windshield, helping it defrost faster.

With that said, the compressor only works up to a point before it shuts itself off, if the air gets cold enough to lower the pressure in a little switch on the receiver. So the clicking on and off noise you heard, provided that it happens at regular intervals of about 30 seconds to a minute, is perfectly normal. In very cold weather, it cycles faster than in hot weather. On the other hand, if it cycles too fast, that means your A/C system has leaked and you are low on Freon.

To disable the A/C for testing purpose, you don't need to unplug the compressor. It's far easier to unplug the switch on the receiver, which is a cylinder on the passenger firewall, right next to the blower in the engine compartment.

Now, if the compressor is making a constant grinding or clacking noise, then the bearing is about to go, and so is the seal. That may explain your leak, if you have one.

If you want to fix the system yourself, you may want to take the van to an A/C shop and have them take out the Freon in your system instead of venting it out into the atmosphere. For a '93, you have Freon 12 and that is expensive nowadays. Most A/C shop would be willing to do it for free since they got to keep your Freon, everybody benefits in that situation.

If you are going to fix your own system, here are a few unsolicited advices:

1) Change all the O-ring seals in your system. The A/C shops should be able to sell these to you really cheap.

2) Inspect the hoses. Part of it is covered by rubber foam, which allows moisture to collect in there and badly rusts out the metal part of the connection. I rebuilt and converted my entire system to R-134a only to have that hose busted on me a few months afterward due to outside rust.

3) Change the orifice tube inside the inlet side of the evaporator. That thing does get pretty badly plugged up, especially if something went wrong with the system. Use a pair of needle nose pliers to pull it straight out.

4) Finally, make sure your condenser is not leaking. Ford condensers somehow are prone to leaking at the solder joints. The A/C shop should be able to check this out for you before they suck out your Freon.

Good luck and best regards

 

how often do you use the A/C in B.C.? if seldom, may not be worth the cost of parts and recharge. A/C does help somewhat with faster defrost in our wet climates.
there are shorter belts available for none a/c Aero's to not drive the A/C compressor, saves on gas even with a/c off, no clutch head to spin up on rpm. believe yours is a V belt '91?

when a/c finally dies on my '96, it will be time for a shorter serpentine, only use a/c maybe 2 weeks out of the year.