AC mystery 2000 Merc Mountaineer

The AC blows cool air. Not cold, not warm but moderately cool. I do not have a temp gauge to measure it, but on MAX AC it feels more like a fan is engaging instead of the compressor. It does not even come close to cooling you off.

I checked the hot to cold and cold to hot and the temp will change. The blend door does move when changing settings. I did the quick blend door fix and it is not stuck.

The AC low pressure was a bit low (couple psi) and I added more to get the psi up to the max for the ambient temp (thankfully I was able to fix the temp display) While adding the coolant, while on max ac, there was a click sound as the PSI rose causing it to drop and then start rising again until reaching same PSI then click then drop. The 13 or so PSI I added did not add anything noticeable to the system when I sat back in the drivers seat. The blowing air was still feeling the same.

I am thinking that it is not a refrigerant level issue, or a blend door issue as I can adjust between vent floor defrost etc and the temp will heat up (best that we can recall, never was cold when driving) winter defrost worked as well. I am thinking maybe a compressor issue but I have never dealt with that before and while I can locate it (right next to the low pressure port, right?) I do not know how to check to see if it is engaging. Things like feel that there after x number of minutes running on max to see if a b and c are happening.

So now I turn it over to the experts before I give up and pay lots of $ to a shop. I hate doing that. A quick background on what I can do with proper directions to follow: repaired the overhead display cracked solder, change brakes, worked on rear shackle replacement, replaced struts in my chevy lumina, replace a throttle sensor and so on.

As an aside, anyone know where I can get a leaf spring rear bushing? When I did the shackles, one bushing each side was stuck. The pass was the lower one and a replacement came with new shackle so we cut it out. The driver side is the upper one which I had no replacement. So I could only replace one shackle because the bolt was stuck to the bushing. We heated it, used a air wrench, air hammer, liquid wrench, sledge hammer and on and on. Just want to cut the old shackle and bolt, cut out the bushing and put in a new one.

Thanks all!

Wow. 24 hours, 52 views and not a single response. Seems just about every time I post up a question it is largely ignored. Not even a simple "this is where the compressor is, see if it is buzzing" or some such. Even when I posted up something about my leaf springs, took forever to get a response.

I am glad I never gave any money to this place. I have never seen a forum so hot and cold over different issues that are easily answered or at least acknowledged. I will probably head over to ask.com and talk about the problem there. Will I be spending more money? Yup, but at least people pay attention.

Bye, don't let the door hit you on the way out.

Welcome Jim, this forum is so big that sometimes threads get ignored as people go down the pages. I opened this because of the "AC Mountaineer" title words. See if any of the possible issues I went over might apply to your truck.

I have a 98 Mountaineer which has had some odd symptoms since the AC "messed up" a few years ago. I started looking harder this year. I had before swapped the temp sensor, checked for freon, tested the HCV, and even swapped the EATC head unit. That was when it first happened, and I've driven the truck rarely since then for other reasons.

Now recently, I finally changed the HCV(heater control valve), and that helped a little. My AC has been almost hot, basically the heater is heating the AC. The old HCV was allowing some coolant through even when "closed."

Next I discovered that the AC did work okay when the truck is not moving, and for the first few minutes it takes for the coolant to get hot. I then discovered that the HVC was opening in "VENT", so I ziptied the HCV shut. The vacuum applied to the HCV is critical, so I know that my EATC is not working properly. I suspect that also causes the problem whenever the truck is moving. I swapped the EATC again this year, and this time nothing really worked, no blower, but the display worked. I think the spare EATC is pretty bad.

The odd thing is that the last three times I drove my truck(July 4th), the AC worked normally. I tried it, with a friend in the truck after time in a salvage yard. It started as typically it would, cold on MAX AC. Then when we took off it didn't warm up, and it worked fine the whole trip back, plus the next two as I went home. I have not touched the MAX switch to turn it off or test anything else. I'm hoping to leave it that way while it's so hot now.

Bottom line, if you have the electronic AC(EATC), those head units will develop internal electrical problems. Capacitors go bad, and they need to be replaced. I suspect that is a problem with any older EATC vehicle.

JimMadsen said:

Wow. 24 hours, 52 views and not a single response. Seems just about every time I post up a question it is largely ignored. Not even a simple "this is where the compressor is, see if it is buzzing" or some such. Even when I posted up something about my leaf springs, took forever to get a response.

I am glad I never gave any money to this place. I have never seen a forum so hot and cold over different issues that are easily answered or at least acknowledged. I will probably head over to ask.com and talk about the problem there. Will I be spending more money? Yup, but at least people pay attention.

Click to expand...

The title of your thread made me skim right over it. Sorry. It could be whoever viewed it had no suggestion for you. It is hot out there, could be 52 views were people with the same issue?

Good luck with "Ask".

I was looking for the mountain man term for the scent they placed on the beaver traps. It was a serious question. So, I googled it.

One of the results was from ask

guy asked "what kind of bait do I use on my sink traps for a large beaver?

The answer was " try a pizza and a bong. I am a low maintenance beaver"

try do a little searching on here... lots of posts this time of year in the northern hemisphere. check for low pressure switch, the high pressure switch... basically the electrical path to the clutch. Your problem is likely incorrect freon levels or possibly a clog (tube). Is your compressor cycling?...

Thank you all for the replies, well except waskly.

The ac blows warm air that feels cooler because it is blowing air. Similar to why a fan makes things feel cooler just by moving the air around. The pressure on the low end has read correct every time I have checked it in various ambient temps. I do not have a gauge for the high end, but am keeping an eye on craigslist.

The ac starts at the same temp it stays at. I cut into the dash to check the blend door and it moved based upon temp settings and vent control position.

I assume the clutch is the wire and pulley looking thing just out of arms reach at the front of the engine that clicks while the ac is running causing the pressure reading to drop every time it gets a little high on the low end.

I am not sure if the compressor is cycling or not, forgive the noob question, but where is it and how do I tell? Is it the cylinder about 8 inches tall with tubes coming out the top almost next to the low pressure port? I do not see a site glass like on older ones I have read about online.

Ask actually isn't bad, I was able to replace the passenger door latch sensor with their help, and all I started with was that the lights stayed on and there was a broken part rattling around in the door. They gave me diagrams, part number, and how to get to it and uninstall/reinstall for 15 bucks or so.

The AC clutch is what you see cycling on and off, on the front of the compressor. It turns on when the pressure gets high enough, and shuts down when the pressure drops below a certain point(low pressure switch).

So your AC clutch, compressor, and freon are not your problem.

Does the AC feel the same as the "VENT" position? Check the HCV by watching it operate by turning the AC on, etc, or by turning the temp setting up enough. The HCV should stay closed(vacuum applied) at almost all times, only heating should open it.

The ac compressor is mounted to the engine and is driven by the serpentine belt. It is on the drivers side of the engine, below the power steering pump. The clutch on the front of the compressor engages and disengages correctly based on the pressure switches. It will make a noticeable clicking noise. You can watch the front of the compressor and you will see the clutch disc be stationary, then hear a click and the disc will begin turning. The cycles will probably be about every 20 seconds I believe. If the system is low the clutch will likely cycle every 5 seconds.

I think the location you are describing near the low pressure port is the desiccant drier canister.

Where is the HCV and how would I determine if it is working correctly? The air stays the same approx temp when it is on vent, max, floor, rear, etc...

I just went out and looked. With the engine running and car on max ac, the compressor (big thing under power steering with a front disc with a triangle and 3 round bumpers/screws) spun for 2-3 seconds every 5-6 seconds without variation.

The part I described before has 3 tubes coming out from it, one of them being the low pressure port.

We tried switching from max ac to 90 degree heat and the vent speed changed and got hot. Switching back to max ac went back to the warm air with the increased vent speed.

Ok, the cycling of the compressor is "most likely" due to low refrigerant. The most likely cause for this IMO is the accumulator bottle leaking. It is the device you referred to earlier --asking if it was the compressor. The insulating foam retains moisture, causing rust to form underneath, which eventually works through and causes a leak. So, you probably need to have an ac shop replace it, and the orifice, while also performing a leak test and re charge.

On my V8, my AC was pumping out nice hot air so I brought it to a local independent rad/ac shop and had the leak diagnosed. I was told the compressor was leaking between the front and rear case halves. I had any remaining refrigerant recovered and brought it home. I changed the compressor, all system o-rings and the orifice tube. I brought it back to the guy and he vac'd the system and charged it up. It has been pumping out ice cold air ever since. My V6 has a leak somewhere now as well and the compressor cycles about every few seconds. I probably have to go through the same process with that one.

It is possible you have the same problem as he said it was common for the compressor bodies to leak like that. There should be some green goo stuck to the underside of the compressor if the leak is a more prominent one.

I can bring it someplace and have them take a look at it. It would be low even though the gauge is showing good pressure on the low port? Also mine is bare metal, no insulation.

I assume this is not a home changeable part because of the pressure and EPA concerns? Did a quick parts search and thats the part I am thinking about with the low pressure port.

If it makes sense that there is a low pressure problem, I will do as 99SportX did and have a standard ac service done in 2 parts with me replacing in the middle.

It sounds like at least you don't have enough freon, if the AC clutch stops every few seconds. Without the compressor running, there will be no real cooling.

If you knew that the freon was all gone, then you could take it apart etc, if you knew what it needed like Eric did. But that requires also changing the accumulator/drier if it's opened for more than say a day. Humidity ruins the driers after a while when exposed.

I'd start by having it checked, then you get a better idea of what is needed. Several times I have done what Eric did, have the problem found, then take it home to do the labor, bringing it back for the vacuum and freon charge.

Will do, would have to wait for the next weekend though, to much back and forth to work.

Now to find a shop that will do the diagnosis on the cheap.

Does the compressor have a part in the pressurized system? In other words, if I mess with it, will I run the risk of evacuating and r134 inside?

The freon is in the whole system. You cannot take any of the lines loose or freon will escape. You can change the AC clutch if it needed one, but that seems to work now.

Be sure to look for evidence of a leak, or have them do that. You don't want to pay them to put freon in, and have it leak out soon after.

How long ago did it stop cooling well? The R134 systems supposedly do lose more freon "naturally" over time. Some people report having to add a can every year. If it leaked any more than that, it's definitely too much to lose and not have something wrong. My 98 Mountaineer I bought in 2003 has never had any freon added, and it apparently doesn't need any now. I don't believe that adding a can once a year is okay.

Hah Don, I was just typing that same statement.

CDW6212R said:

The freon is in the whole system. You cannot take any of the lines loose or freon will escape. You can change the AC clutch if it needed one, but that seems to work now.

Click to expand...

We have had the car for about 16 months now, and the prev owner was reported to do a can a year. I myself have added maybe 1/2 of one large 18oz net weight can of "EZChill R-134a Refrigerant Plus Oil With System-Safe Leak Sealer" I always stopped from adding more because I was shooting for the safe operating range on the included gauge. If it is safe to dump the whole thing in and see what happens, I can go do that now and see how the thing works in the am.

You are definitely losing refrigerant. I would find the leak, fix it, and enjoy reliable and cold AC. I added some to my V6 and it worked for a while, but it was all lost after not much time. A can a year is way too much. It shouldn't lose any refrigerant if all system components are in proper condition.

I would add the rest of that can, you are nowhere near to being over full, with that much clutch cycling. Compared to that, it should run for a long time before cycling off.