'95 Taurus AC Questions

[overknight]

I have a 1995 Ford Taurus GL wagon with the 3.0 L engine with 103,000 miles. The AC compressor clutch is not engaging. I haven't done any electrical checks yet, but I understand that if the Freon pressure is too low, the compressor clutch won't engage. The Haynes manual shows a two-wire connector going to the front of the compressor, near the clutch, that energizes the clutch, but mine has a four-wire connector on the back of the compressor. Which of these wires should I check to see it the clutch is getting voltage?

If there is juice, is there any way to check the Freon pressure without gauges? If I need to bring it to a shop, I will, but I'd rather not invest much into this car.

How is the AC clutch removed and replaced? Are there any special tools needed? Does the entire compressor need to be removed?

Despite the overall poor reputation of these cars, and I've had the usual problems (tranny rebuilt and radiator replaced at 77,000 miles) it's been a good car that has given me good service for the past 11 years with minimal maintenance. I do "exercise" the AC system regularly during the winter to keep the seals lubricated. Since it's paid for and this is the only thing wrong with it, I'd like to hang onto it.

Thank you.

[shorod]

Are you sure you're looking at the A/C compressor and not the alternator when you say there are 4-wires going into the back? I'll have to check my service manual tonight, but if there are four wires going to the back, two of them have to make it to the front to engage the clutch field coil and I'm not sure what the other two would go to.

And to properly check the level of the R-134a refrigerant, you'll need a set of appropriate gauges.

-Rod

[overknight]

Thanks, Rod. Yes, it's absolutely the compressor. There's a round connector on the back with four wires.

If I can find out which wires energize the clutch, I can 1) determine if there is voltage going to the clutch, which would mean there's enough freon in the system and the problem is just the clutch, 2) patch 12 V into these wires to manually engage the clutch, which would be the best go-no go test. Sound right?

If it is the clutch, are they difficult to replace? Are any special tools needed? I'm pretty good with cars, and I am pretty flush with tools (there's never enough, though...) but I have no experience with automotive AC.

Thanks again.

[shorod]

The wires for the field coil are the black wire and the black/yellow wire. They are sourced from the Constant Control Relay Module (CCRM) at terminals 16 and 23 respectively and driven by the PCM, terminal 21 at the CCRM, pink/light blue wire.

All indications in the factory service manual are there are only two wires going to the compressor, and these two wires are for the field coil.

There are some special tools shown in the service manual to remove the clutch to get to the field coil, but I don't know how necessary they are. Since I'm not totally convinced that what you're looking at is the compressor (sorry to question you on this one) I'd hesitate to attempt to apply fused battery power straight to what you consider the field coil and see if the clutch engages.

-Rod

[tripletdaddy]

So, you have watched and listened to the clutch and it is not engaging at all? Has the car ever had a refrigerant leak before? They seem to have some history of developing leaks. Wished mine lasted as long as your without a leak. This could be either electrical or low charge. You could get a cheap low side gauge that I find handy for checking pressure when I need to recharge the system. They typically have a colored dial for the different charge ranges. If there is something in there, you should get sufficient pressure to kick on the clutch, even if it is discharged 50%. If you wish, a brief discharge at one of the gauge ports can give you an idea of the pressure. This will indicate if you have an electrical issue rather than a refrigerant issue.

Or, you could just takle this from an electrical approach. Trace the wiring to the two sensors that are screwed into the lines. One should be connected to the accumulator/dryer or to a line to it, and the other is
close to the compressor. If like mine, it will be behind the comp between the rad and the engine. They should look similar but the low pressure has two wire and the high pressure has four. There should be a purple, hot wire to the accumulator sensor and a red/yellow wire leaving to the compressor sensor. The first sensor will close(on) at 45 psi and open( off) at 25 psi. It also will not let the clutch run if the system pressure is too low, as you said. Normally, via a pink/lt blue wire, the hi pressure, compressor sensor will let the power pass on to the computer and ccrm, and then to the clutch, however it will open, cut off the power when there is excessive pressure. From the ccrm the wires to the clutch are black/yellow, hot and black, ground. The other two wires at the sensor are a black, ground, and tan/lt green to the computer. They are for signaling hi fan speed based on pressure.

Speaking of which, have you verified the fan comes on when you turn on the ac?

Hot wiring the clutch is doable with both a hot and ground you supply, but I highly recommend disconnecting the wire connector so as to not burn up anything expensive, ccrm, pcm.....

[shorod]

So, tripletdaddy, are there really 4 wires going to the compressor? Are "the other two wires at the sensor" located in the same connector as those for the field coil and located on the back of the compressor? That's the part that has me really confused. I don't want Overknight spending a bunch of time troubleshooting the wrong pulley-driven part.

-Rod

[angus10]

Just remove the plug from the low side switch (the one closest to the ACCUM/drier) Bend a paper clip and jump the plug while the car is running (do not let the paperclip touch anything else) and see if the compressor turns on. If it does you are low on refrigerant. If it doesn't you have a prob. that should be checked out by a pro or you gonna ruin something or get hurt. You can do this for the hi side sensor too, but don't leave the jumper in long, and don't mess with the hi side too much.

[overknight]

Thanks, everyone. I'm a little busy today, but I stopped by a Pep Boys and picked up a can of freon with a gauge. I should be able to try to track some wires to check voltages and check the pressure tomorrow. What system pressure would I expect to find if the compressor isn't running?

I'll let you know what I come up with. Thanks again.

[tripletdaddy]

Hmm, I'm not sure I'm to be honored and feel respected, needed and appreciated.......or.......feeling used, placated and being setup.

Oh well, I guess I'll be a willing go to gopher. I think at least I won't loose too much on this deal,.....like a pcm!?!

I will settle two issues here, one electrical and the other refrigerant. Firstly, on the matter of two, four or six wires going to the compressor, the answer is, there are six wires going to the compressor vacinity. They all originate from the same wire loom, bundle that goes between the alternator and ps pump and joins the alt. wiring. As Rod and I both expected, there are ONLY TWO wires that directly connect to the ac compressor. They connect to the top of the clutch field, which is right behind the serpentine belt pulley. And if anyone is wondering, the 3.0 and the 3.8 engines have the same ac compressor, accumulator and sensors arrangements. I know this because I just looked at them both in the "sheet metal." And, the compressor is the lowest, frontmost accessory on the serpentine belt under the power steering pump.

Now, on to the remaining four wires. They connect to the hi pressure/hi fan relay switch, which I figured was the cause of the confusion all along, as this switch is located behind the compressor, screwed into the hi pressure line coming out of the back of the compressor. It has a square four wire connector to it. As all of this is squashed together and interconnected behind the compressor, it could appear that the compressor is the recipient of the 4 wire harness, instead.

Now for the second issue at hand, also putting myself, my vehicles and my wallet at peril, , I will address issues of ac refrigerant pressures. In order to get the ac comp clutch to engage, the MIN. pressure as measured at the low side ac clutch cycling switch is 45psi, which typically should be very close to the low pressure side gauge and charge port. As it turns out, when the ac isn't on, nothing is heating or cooling it and the refrigerant pressure inside the ac has equalized throughout it, us technical folks like to say, the system is currently static and the conditions are steady state. It's just a fancy, though concise way to say that you can measure the pressure and other information anywhere in the system and get the same results. So, for example, if you measure 45 psi at the low pressure port,it will the same at the high pressure port. So in short, at anytime, if you have less than 45 psi at the low port, it won't come on.

Now, on to filling the system enough. These systems have a known volume, which the smart folks at Ford optimized the right amount of refrigerant to use in the system, so all an ac tech needs to do is to put the right weight of refrigerant in it, which often is on the underhood decal. Typically, these systems take two to three pounds. A measuring container that converts weight to volume can be used instead of a weight scale to put the right in. Anyway, without the proper equipment, most of can't do it right or well. But, as a rule of thumb, I have determined that these systems have enough refrigerant when they have 65 PSI at 55 to 60 deg F with the ac system in a static, steady state condition. (most conveniently measured at the low pressure port) So, below 65 psi, you most likely don't have enough in it.

So, as said before, the ac will kick on at 45 psi or higher. Only the high pressure switch will turn the compressor clutch off when the system pressure is too high at 430 psi, which is rediculously high! It will return closed at 250 psi allowing it to run. The hi fan switch will switch on the fan to hi at 325 psi and off at 275 psi, returning the fan to the normal low speed setting, which is turned on by the pcm.

AC systems are counterintuitive, so what I'm going to say next doesn't make much sense, but as said before, when the pressure is 45 psi or higher, the compressor comes on. BUT, when the low side pressure GOES DOWN to 25 psi, it kicks off. Then the pressure will start to rise till it hits 45 psi again, the compressor comes on, then off at 25 psi. So, say you have 44 psi when you start your car cold. The ac won't come on. Then, if it gets hot enough to get the 44 psi to 45 psi, or you add more refrigerant to increase the pressure, the comp will come on, Then it will real quickly compress the rfrg (or just screw, I guess that would depend on the compressor, nah, screw comp will still compress, screwy , sorry, that's from a brake discussion here) to 25 psi and then cutoff. But, because there is not enough rfrg to do much cooling (or more correctly, technically speaking, remove heat), it will immediately return to 45 psi, kick on the comp and so on. This is known as short cycling. Another words, if it short cycles, it needs more refrigerant.

Whew! I hope that covers it. I need a nap! Good Night!

[shorod]

Excellent information! Thanks for clearing all of that up. And certainly it would not be a good idea to apply 12V directly to any 2 of the 4 pressure switch wires.

-Rod

[overknight]

Wow! Thanks, Tripledaddy. I'm definitely going to save this. Those two wires going to the clutch are darn near impossible to see, and I couldn't even get my fingers in there to feel for them. I'll try again when I can get it up on some jack stands.

As it turns out, I won't be able to work on it until next week - I brought my Mom out here for the 4th of July in her car (92 Plymouth Acclaim with 22,000 miles). It gets driven to work, the supermarket and church. Needs some TLC...

Thanks again, everyone. I'll let you know what I find when I get the Ford back. Have a great Fourth of July.

[overknight]

I've finally had a chance to check the AC out a little farther.

A few weeks ago, I bought one of those Interdynamics AC gauges with a can of R134-a refrigerant. The gauge has four color-coded sections: green is 0 - 25 psi, which is "low", blue is 25 - 45 psi, which is "filled", yellow is "alert", which is 45 - 65 psi, and red is 65 psi and above, whci is "warning". I connected it to the low pressure side and it read somewhere in the green range, i.e., low. I placed the refrigerant can onto the installation receptacle, and I noted the compressor to engage when the pressure reached about 50 - 55 psi. The pressure would then steadily drop to 25 psi, and the compressor would disengage. Sounds like the short cycling Tripletdaddy described. Once the can was empty, the pressure stay below 25 psi, so the compressor remained unengaged. Since I only had one can of refrigerant, that was the end of that day.

Today, I bought two more cans of refrigerant. The scenario was the same as with the first can, which was more short cycling. Since Tripletdaddy said that the capacity of most systems are 2 - 3 lbs., I've now added over 1.5 lbs. Also, after adding this second can of refrigerant, I noted an approximately 6" diameter puddle of what appears to be a greenish fluid. Although I could not quickly determine where it came from, it IS NOT antifreeze. I am therefore hesitant to add a third 13-ounce can to the system.

I'm on the fence if I should spend the money on what I'm betting will be a rebuilt compressor for a 13-year-old car. However, it's paid for, and frankly, I like this car. Since I've invested in a rebuilt transmission, a new radiator with all hoses, and new tires and brakes within the past five years, and it's been exceptionally reliable and perfect for my needs, my inclination is to fix it and keep it. I'd appreciate further suggestions on 1) if this is a prudent course of action, 2) should I try adding the third can of refrigerant, 3) how much I should expect to pay for a rebuilt compressor (plus system evacuation and recharging), and, 4) basically on how I should proceed.

Thank you, everyone.

p.s.: Sorry, tripletdaddy, I misspelled your name on the previous post (left out the second "T"). Triplets? God bless you. How old are they? I hope they slept well. All females? Triple God bless you...

[shorod]

If the cans of refrigerant have UV dye in them, that's probably the fluid you are noticing, and you probably have a large leak. Figure out where the leak is originating from before spending any more money on cans of R-134a.

Also, there should be a sticker under the hood that specifies the oil and R-134a capacities. If you are putting that much R-134a into the car, it's possibly out of oil as well.

-Rod

[tripletdaddy]

Briefly, ditto on leak and dye, find it first, then proceed. I would have expected you to have heard a hissing sound with this leak, but if you put in green dye....

A junk yard compressor or whatever is leaking is an option for less. I suggest you read a parallel thread here http://www.automotiveforums.com/vbul...d.php?t=915123
to help cover some of your questions.

No problem on name mangling, I tend to ignore stuff like that. Abrev. are ok too. I do, no offense meant to anyone. I figure typing isn't everyone's thing and for as particular as I am about mine and my grammer, and I still make mistakes, I can't be too picky about others. I only get annoyed or frustrated when folks just can't be understood, don't make sense, and garble and mix together a whole bunch of points that can't be made sense of.

Yes, I had the three in one deal. It came with a nonrefundable, no return policy. We have three 7.5 year old boys. Oh, boy. Sigh. So full of vim and vinegar and into everything.....including my stuff, tools, etc......sigh. They're just a little intense for me. My brother and I were not. I don't know why everyone asks how they are, when us parents are the ones all worn out and tired?!? Thanks for noticing.

[overknight]

Here's the final (I hope) update:

I was faced with having to drive Boy Scouts up to summer camp without AC, so I brought the car to one of those franchises, who's biggest benefit is that they're walking distance from my bus stop. The diagnosis: a big leak in the AC discharge and suction assembly. The tab: $670.00. This would include replacement of the receiver/drier, also. I gulped, talked it over with DW, thought about it some, and finally told them to go ahead. I never had any intention of spending this amount of money on a 13 year-old car with 111,000 miles, but I my thoughts were 1) there's nothing wrong with this car, 2) it's paid for, 3) 111,000 miles isn't much for a 13 year-old car, and 4) since a transmission rebuild and new radiator were done within the past five years/30,000 miles, and brakes, hoses, plugs, cap and rotor were replaced within the past three years, and oil changes are done every 3,000 miles (it doesn't burn any oil), I should be able to get another few years out of it. Hopefully, I'm right.

After replacing everything, they put a vacuum on it overnight, and it held. The AC is ice cold, and on the return trip the scouts were thrilled to be in the first AC in a week.

Small problem with the door locks, now. Fixable, but a POA. I'll start another thread...

Thanks, everyone.