Automotive Air Conditioning Information Forum (Archives)

Provided by

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

AC Works... then it doesn't?

JudoJNoble on Fri July 26, 2013 2:20 PM User is offline

Year: 2006
Make: Ford
Model: Taurus
Engine Size: 3.0L
Refrigerant Type: 134a
Ambient Temp: 77.2
Pressure Low: 49
Pressure High: 115-130
Country of Origin: United States

So in all my searching, I've seen issues like this mentioned, but haven't actually seen definitive answers about what the problem could be. Any time someone says their AC doesn't work in some forums, some people jump on immediately and say they need more freon. That may very well be the case; but when the A/C works sometimes, that doesn't always make sense to the person with the problem. So I'm hoping to put a bit more information out there, and get some more informed opinions.

First off, this isn't a blower motor problem. The blower works great. A friend of mine had an issue with her car recently, where the blower motor wasn't always working, and that was a Blower Motor Resistor problem. Anyone who stumbles across this thread with an intermittently working blower should probably check that out. Took me $30 and less than an hour to fix it.

Anyway, my A/C works when I first start my car. It also seems to work pretty well when the outside air temperature is not too hot. It's not a matter of blowing cool air simply because it's cool outside, either. I've seen that response given more than once, and it does not apply here. The A/C is definitely cooling the air at first, as you can see by my info below. And if it doesn't get too hot outside (or in the engine compartment), sometimes it might not stop working. But when it does stop working, it's a noticeably marked change between cold air and warm air.

My first thought was to change the Ambient Air Temperature sensor. After all, if the sensor was telling the car that 90 degrees was actually 32 degrees, then the compressor wouldn't cut on at that point. Unfortunately, that 18 dollar fix didn't fix anything.

So I got some gauges and hooked them up, and I'm hoping that someone can help me figure out what the problem is... and maybe others who are experiencing similar (cools until it's hot) problems can get some ideas, as well.

Thanks in advance!

Vehicle: 2006 Ford Taurus, 3.0L sfi V6
Outside Temp: 77.2F
Initial A/C Output: 56.4F

According to the Shop Manual, I believe the normal pressures at operating temperature and 77 degrees outside ambient would be L: 30-50psi, H: 145-250psi

Gauge readings when first connected: L: 49psi, H: 65psi
Gauge readings when car started: L: 47psi, H: 95-110psi
Gauge readings as car warmed up: L: 49psi, H: 115-130psi

At operating temp, the compressor would cycle on for 2 seconds, then off for 3 seconds; and there would be a “whirring” noise when it was engaged. Eventually, compressor stopped, and…
Gauge readings when compressor stopped: L: 55psi, H: 81psi… 75psi… dropping
(I didn’t get the gauge readings with the car completely warmed up, yet before the compressor cut off.)

Giving the compressor plate a good rap would get it to engage (cycling on and off) for a bit again. I did this a couple of times. Before I did it the second time…
Gauge readings with compressor stopped: L: 61psi, H: 70psi
The compressor cutting on would jump the high side to 130-145 the first or second cycle, and that number would drop off every time it cycled, until it quit cycling (compressor stayed disengaged) again.

As a side note: when the compressor engaged, it was definitely pulling on the engine. I had a bag on the accelerator to keep it near 2000 rpm, and when the compressor was cycling, the rpm would drop and ride from 1200 rpm when the compressor was not engaged to roughly 600 rpm when the compressor was engaged. When the compressor stopped engaging at all, it climbed back up around 1800/2000rpm.

When all was said and done, the A/C was blowing air at 89+ degrees (quite a bit warmer than outside temp, but likely not warmer than engine compartment), and when I cut everything off and eventually pulled the gauges, they were sitting at:
Gauge readings with everything off: L: 63psi, H: 90psi

So… any educated ideas as to what the problem is?

Also, any idea whether or not I likely damaged anything by running the A/C to get as much as I could until it quit? What about by "forcing" the clutch to engage by rapping on the compressor plate after it had quit?

Thanks for your help!

Edited: Fri July 26, 2013 at 2:31 PM by JudoJNoble

Dougflas on Fri July 26, 2013 2:42 PM User is offline

First step I'd take is recover the charge of R134 and recharge it by weight to factory charge amount. More systems are repaired by putting in the correct amount of refrigerant than replacing parts. R134 has a tendancy to leak due to small molecules.

Then come back here with readings at 1500 rpm.

GM Tech on Fri July 26, 2013 4:27 PM User is offline

You answered your own question--you said giving the compressor a good whaaap made it engage- there-in lies your problem- the air gap is too wide between the clutch driver and the pulley face- due to wear- remove clutch driver and remove a shim- then the air gap should be near .020" anytime someone says their a/c is intermittent- air gap is my first thought.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

JudoJNoble on Wed July 31, 2013 1:02 AM User is offline

Thanks for all of your replies so far!

Don't worry, I will definitely keep this updated so it might help anyone else having similar problems. And I might need a little more help, to boot.

I was out of town for the weekend (saved my driving for the evening hours, for more bearable temps), so I didn't get anything accomplished. This evening, I reached in and checked the air gap... wow is it tight trying to reach all the way down between the firewall and the serpentine belt to the compressor at the bottom!

The air gap does indeed appear to be a little bit too large. Couldn't get an exact number on it reaching down from the top, but it didn't seem much over the .030 maximum clearance. Maybe that's why it is able to engage at first. I'm still confused on why it would engage without any trouble at first, or during lower temps... but would stop engaging when the car/weather heated up sufficiently. Any ideas on that?

Either way, I will definitely try fixing the air gap issue, and seeing if that fixes the problem. To that end, I've heard somewhere about simply tightening the center bolt to close the air gap. What is the likelihood that this could work? I assume I will have to figure out how to get the clutch plate off in that tight space, and remove a shim or two; but if tightening the center bolt would indeed work without causing further issues, that seems like a preferable route.

Thanks again!

mk378 on Wed July 31, 2013 1:27 AM User is offline

+1 on the clutch gap.

The physics behind that are that the resistance of copper wire increases with temperature. The higher resistance of a hot clutch coil means that for the same voltage, it generates less magnetic force. If the clutch gap is marginal, the plate will not pull in unless someone hits it with some external force.

Simply tightening the center bolt doesn't change anything. You'll need to remove the bolt, remove the clutch plate, and take some of the shim washers off of the shaft. The thickness of the shims sets up the gap.

GM Tech on Wed July 31, 2013 7:28 AM User is offline

You also have a Taurus-- they are known for CCRM (constant control relay module) a/c portion failures--there are several write-ups on how to fix, replace, or bypass this bad boy.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

JudoJNoble on Thu August 01, 2013 12:07 AM User is offline

Thanks for the responses, and for the explanation of the physics! That definitely makes sense, though at the time the intermittent issue was not making sense to me.

You were correct about the clutch plate gap being too wide. I hope that was the only issue. It didn't look like there was any way I could get to it where it sat, though with a swivel head on an extension it may have worked out going through the two holes that are lined up on an '06 Taurus. Regardless, I'll include notes below about getting to and removing the clutch plate on an '06 Taurus, in case someone else with the same problem finds this thread.

As for my situation: the air gap was at least .050 inches (acceptable tolerance is .014-.030). When I got the clutch plate off, there was only one spacer/shim. It was up inside the clutch plate itself, and I had to pick it out. I didn't lose any shims. There was only one. It was roughly .040 inches thick, so I put it on the outside of the clutch plate, and put the plate back on with no spacers. Once it was back together, the plate still spun freely, and I was able to barely push the .015 in gauge into the gap... so it was right around the .014 minimum tolerance.

The car isn't drivable yet, but in 75 degree weather this evening, the a/c was blowing below 60 degrees for over 15 minutes without the compressor quitting. Hopefully it will work during an extended trip in the middle of 90-degree weather.

I will definitely give an update when that test happens, within the next few days to a week or so. I'd rather give it the performance test than the pressure gauge test, as the latter loses a little bit of freon each time.

- JN

Now, as for getting to the clutch plate on a 2006 Taurus:

In order to remove the clutch plate without disconnecting the compressor, I dropped the entire sub frame. Noticing (too late) the two holes through the firewall that line up with the center of the clutch plate... I would try a small 8mm socket on a swivel head and extension, through the two openings that line up with it, though I can't guarantee that there would even be enough space between the compressor and the firewall to remove the clutch plate at that point. If that does work, all you'd need to do is remove the plastic shroud in the wheel well and get a tool to hold the clutch plate still.

Anyway, here's what I did this evening (I haven't tried going through the openings), and what seemed to work with little issue an an '06 Taurus:

- Loosen the lugs on both front wheels
- Raise the car, and place jackstands at the reinforced jack points on the rails
- Remove the front wheels, and the single bolt holding the brake line to the body on each side (10mm)
- Remove the front half of the plastic shroud inside the passenger side wheel well, and the shroud underneath the front [under the radiator] (3 phillips head screws in the wheel well... and nine 7/32" plus three 5/16" on the front shroud)
- Remove the three nuts holding each of the strut towers to the body in the engine compartment (13mm)
- Remove the bolt connecting the dogbone-shaped brace coming from the strut tower to the brace coming from the alternator (13mm).
- Disconnect the hose to the air filter box, and the cables to the battery
- Support the driver's side subframe, and loosen the two large bolts (18mm) holding it to the body (one in front and one at the rear of the subframe). Lower the driver's side subframe a few inches. Check hoses and wires, though there shouldn't be any binding up.
- Repeat the process on the passenger side, lowering that side until the air compressor clutch has fully cleared the firewall, so it can be removed. The passenger side should be lowered much further than the driver side, though if any pulley (most likely the tensioner) comes into contact with the firewall, just lower the driver side further, to reduce the angle of the engine tilt.
- Hold the clutch plate still while removing the center bolt with an 8mm socket. Although you really should use a specialized tool to hold all three dampeners still at the same time, I don't believe the tool at AZ will work for this. So you should make your own or find one. I don't recommend doing what I did, but... I used the open end of a wrench to "hold" one of the round dampeners, and braced the other end against the subframe to keep the plate still while turning the center bolt.
- Be sure not to lose any of the shims when you remove the bolt and clutch plate. Check the end of the tines on the compressor for any shims stuck on there. Determine which shim(s) need to go between the clutch plate and compressor -- if any -- and keep the rest on the bolt, but on the outside of the clutch plate. Tighten the clutch plate bolt to 13NM or 10 ft/lbs (for 2006 Taurus).
- Reassemble everything, being sure to guide the strut towers bolts into the right holes into the engine compartment (a 13/16" socket on the main strut nut can help with this).

Note: When I got the compressor put back together and the subframe reattached, I decided to reconnect the battery and air filter and give the car a start to see if the compressor clutch was working properly. The car started and immediate sputtered and died. I tried again, revving the engine, and it sputtered and died again. Checking everything, I found that one of the large vacuum hoses had become detached from the rear top of the engine. I think it might have been the PCV valve, if memory serves from earlier, but not 100% sure on that. Either way, I popped it back into place and the car (and compressor clutch) worked just fine.

I plan to finish putting everything back together tomorrow when I have more light, and I'm hoping this fixed my problem with intermittent cooling A/C.

A few links that you may or may not find helpful in this situation:

This is the closest tool I could find that was readily available to hold a clutch plate still... though it doesn't seem like it would work with the 2006 Taurus.

Edited: Thu August 01, 2013 at 8:10 PM by JudoJNoble

JudoJNoble on Thu August 01, 2013 12:09 AM User is offline

Also, thank you for the info about the CCRM.

Although the statements about the clutch plate being too wide were definitely correct, I'm still hoping that was the only problem at the moment. Even if it comes back that it is working fine (which I will let you guys know), I will keep this bookmarked and keep the CCRM thing in mind for the future.

All responses have been greatly appreciated.

Thank you!

JudoJNoble on Thu August 01, 2013 9:01 PM User is offline

Driving around today for a while (roughly 75 degree outside air temp, and quite humid), the a/c was cooling at a pretty constant 56 degrees.

When I got home, I let the car run for a bit and checked the pressures. Here's what I have:

Outside air temp: 74.5 degrees F, humidity 95%
Controls set on Max A/C, Full Cold, Low-Med Blower
RPM: 1700-2000

Low: 31 psi
High: 110-130 psi
Temp at vents: 53 degrees F

Factory specs at 74.5 degrees F, 30-60% humidity:
Low: 29-48 psi
High: 135-240 psi

Notes/Question 1: The compressor would be on for a few seconds, then off for a few seconds, and repeat. The car was running at 1700 rpm, and would increase to roughly 2000 rpm when the compressor would cut on, and drop back to 1700 when the compressor was off. Before cutting on, the high side would be at roughly 110 psi, and it would increase to roughly 130 psi over the few seconds that the compressor was on, and then drop to about 110 psi over the few seconds that it was off. Any thoughts on this being normal, or a symptom of something abnormal?

Note/Question 2: Specs are for 30-60% humidity. How would the 95% humidity alter the system readings?

Fixing the air gap seems to have fixed the primary symptom for now. I will definitely say something if that changes during a longer trip in higher temps.

Thank you for the input so far, and for any further thoughts/assistance you have to offer.

webbch on Thu August 01, 2013 11:09 PM User is offlineView users profile

Still not sure how much refrigerant is in the system. On my car, I'd recover and recharge before continuing. If I wasn't able to do that, I'd add a little refrigerant, watching to see if the high side pressure increased. If the high side pressure goes up, then it at least suggests the compressor is ok. Also, put the blower on high during your tests....

mk378 on Fri August 02, 2013 10:37 AM User is offline

You have symptoms of a CCOT system with low charge -- poor cooling, compressor cycling rapidly, and a low high side. Like webbch said, the best next thing to do is to recover and recharge by weight. (The second-best next thing to do would be to try to top it up by temperature / pressure.) Also inspect the system for leaks, and dose it with UV dye if it isn't already present. If you see the traces of oil normally in the ports is dyed yellow green, there is UV dye in the system-- which means you can look for leaks with a CFL blacklight or other UV lamp.

Edited: Fri August 02, 2013 at 10:47 AM by mk378

JudoJNoble on Fri August 02, 2013 9:35 PM User is offline

Haven't had a chance to put gauges back on it yet, but tested it with some extended driving today in hotter weather...

Driving around in 90+ degree weather, the a/c was pumping out air at about 70 degrees, sometimes in the 60's. So fixing the gap definitely helped, but it's not yet where it needs to be. Hoping to get some gauges on it again, add some Arctic 134a (until the high side is reading the proper range) sometime in the coming week, and check for leaks.

Edited: Fri August 02, 2013 at 9:55 PM by JudoJNoble

JudoJNoble on Thu August 15, 2013 1:42 PM User is offline

After fixing the compressor gap, the a/c was cooling about 20 degrees, so I figured the freon was low. But it kept cooling at about 20 degrees cooler than the outside temp, so that was better than before.

The last time I used the a/c before putting freon in, though, it was not even cooling 20 degrees anymore. When I pulled the high side cap off, there was a bit of pressure underneath it that I had not experienced previously. I was worried that there was a bit of a leak, but was there to put freon in the system and so I did. With the car warmed up, I connected the gauges.

Idle: ~800 rpm
Outside Air temp: 80F
Temp at Vents: 70F
Low: 32 psi
High: 140-160 psi

Target pressures at 80 degrees are:
Low: 32-52 psi
High: 150-260 psi

With the compressor running, I added a can of freon (and some dye). The final results were:

Low: 34 psi
High: 225 psi
Temp at Vents: 46F

So everything looked great! Except for a nagging feeling about that high side connection. After cutting the engine and disconnecting the gauges, I put some soapy water in the high side connector (on top of the schraeder valve); and sure enough, it was bubbling. The o-ring on the valve was slowly letting gas out.

So I found a tool that allows you to replace the schraeder valves without losing all your freon, and yesterday I replaced both the high side (10mm valve in 2006 Taurus) and low side (8mm) valves. After checking for leaks with the soapy water, I blew the water out and let it dry before connecting my gauges. After topping it off with another can of freon, my final values were:

Outside air temp: 75F
Engine idle: 700 rpm
Low: 35 psi (target is 29-48 psi at 75F)
High: 190 psi (target is 138-238 psi at 75F)
Temp at Vents: 40F

So for now, it looks like everything is good to go. I looked around the system and couldn't find dye leaking out anywhere, but if the system doesn't keep running well I will definitely update the thread.

Initial symptoms:
System cooling intermittently.
Blower working fine, but compressor stops engaging at higher temps (engine and/or ambient), and engages when clutch plate is rapped.

First issue:
Air gap beyond specs.
Reduced air gap of clutch plate. This fixed the compressor problem, though the car was only cooling about 20 degrees from ambient.

Second issue:
Low on freon.
Slight leak at schrader valve, likely due to age of o-rings and repeated usage of manifold gauges. Also possibly due to increased pressure in system resulting from compressor functioning properly.
Replaced high and low schrader valves, and recharged until within specifications.

Final result:
System seems to be working properly, for now.

Leggie on Tue August 20, 2013 10:48 PM User is offline

Originally posted by: Dougflas
First step I'd take is recover the charge of R134 and recharge it by weight to factory charge amount. More systems are repaired by putting in the correct amount of refrigerant than replacing parts. R134 has a tendancy to leak due to small molecules.

Then come back here with readings at 1500 rpm.
All auto A/C systems leak. As long as there are hoses and o-rings and a shaft seal, some will always leak just as balloons shrink with time.
If you don't know the service history or know its never been serviced since new, that's a good start.

I'd go a step further and document how much was recovered and if service history is known and calculate the leakage rate to see if its a normal diffusion + shaft leak or if there is an abnormal leak.

A diffusion leak only needs refrigerant replenishment. Abnormal leak involves oil loss and if service history is unknown, it maybe severely starved of oil or severely over oiled (from use of Lube + refrigerant consumer recharge products).

Chick on Fri August 23, 2013 8:37 PM User is offlineView users profile

You fixed the common clutch gap problem (probably due to constant cycling due to a low charge) but "appear" to have a low charge.. Recover the refrigerant, pull a deep vacuum and recharge the proper amount back into the system (without breaking the vacuum).. You should be fine... Do it right and you'll do it once..
hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.