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AC had a melt down- maybe?

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Old 06-15-2017, 08:14 PM   #1
billschroeder5842
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Default AC had a melt down- maybe?

Hey all!

I had a situation on the commute home today in my (new to me) 89.

I was in bumper to bumper on Texas 114 (yeah- go metroplex) inching slowly as there was an accident up ahead. The ambient temp was 96 out but it got real hot under the hood due to no air moving other than the fans.

My car was running well, with the AC on blowing reasonable and the temp gauge crept up to 240.

I then noticed a burning rubber/chemical smell and looked over to the passenger fender and there were faint wisps of smoke coming out. Then the AC shut off.

I pulled over and looked under the hood and saw that the smoke was coming from the compressor pulley/clutch area. I figured that the clutch had locked up. I kept the AC off and sweated during the rest of the 14 miles home. With the AC off, the car ran great, normal (200-220) temps and no smoke.

In my garage I noticed that there was a bit-- not lots about a table spoon-- of fluid splashed on the under hood and on the compressor top, behind the belt. I spun the compressor and it felt normal. I then turned the key forward and pushed the AC button. I tried to spin the compressor and the clutch had engaged. Huh- all normal?

So, is my compressor fried or is there some type of high pressure cutoff switch and "blow off valve" for the fluid? I ask as my old Mopars had those features.

I'll let the engine cool a bit and start her and put the AC on to do some diagnosis.

Any thoughts?
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Old 06-15-2017, 10:30 PM   #2
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*update*

I read up on the trusty FSM and sure enough, there is a "High Pressure Relief Valve" that "allows refrigerant to vent to the atmosphere" when the high side pressure reaches 440psi.

I went out and started the car and flicked on the AC and all systems were normal. No abnormal noise, fluids, smells...etc. I took the car for a couple mile drive (it was about 78 outside) at varying speeds with a few on/off systems and everything was normal.

The only thing I noticed when inspected after the ride was that there was a small bit (1/4 tea spoon max)of residue that was on the underside of the hood. It was not liquid but black, wet and granular. My first impression is that it was "left over" and was the over sprayed when the clutch cam on for the first time since the road side stop.

So, what do you think? Did the extreme heat (240 on the gauge) with no real air movement cause the system to over pressurize and release or is it something different?
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Old 06-16-2017, 08:17 AM   #3
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..... My '93 Suburban would do that (relieve pressure) if I didn't start moving within 20-30 seconds of a hot start ... it had a fan clutch that would be free wheeling and wouldn't pull sufficient air across the condenser ... I fixed it with an electric fan that came on with the A/C ... I'm surprised your fan(s) weren't pulling enough air ... could have been the extreme under hood temps that helped the pressure to spike .....
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Old 06-16-2017, 12:40 PM   #4
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Sounds like you're over-vetted Bill. Stick to the Z!
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Old 06-16-2017, 02:04 PM   #5
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Sounds like you're over-vetted Bill. Stick to the Z!
Ha!

They are different; Blondes vs Brunettes!

However, if I had to pick one, the Z is the keeper.
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Old 06-16-2017, 02:37 PM   #6
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Very possible AC clutch is bad. Just take this info and see if it fits.

I have seen where things get so hot with an older clutch, they will start to come apart. The black rubber substance will come out when it hottest on to the pulley, belt or compressor. Then when it cools the rubber gets hard again and the clutch will work. The question is how long and when will it start slipping or locking up.
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Old 06-16-2017, 02:44 PM   #7
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I have seen where things get so hot with an older clutch, they will start to come apart. The black rubber substance will come out when it hottest on to the pulley, belt or compressor. Then when it cools the rubber gets hard again and the clutch will work. The question is how long and when will it start slipping or locking up.
Thanks- this very well could be the case. The smoke was rubber smelling and the residue had a rubber-ish feel to it.

I'll keep an eye on it-- and way to inspect the clutch short of taking everything apart? Also, if it is super hot under the hood, I might give it a break and roll the windows down.

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Old 06-17-2017, 12:04 AM   #8
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Talking out of school here because I am just now beginning to read about it.

Much (Very much, actually) is made of airflow over the condenser in technical manuals.

This is critical and it affects system pressure, especially at the margins. (At least this is what I am given to believe as of right now.)

Question: Do you have debris in front of or behind your condenser?
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Old 06-17-2017, 12:30 AM   #9
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Ya know, I always noticed the fans come on when the AC was running. I just assumed (I dunno why? Because I was focused on the engine, I guess?) it was to help keep the engine cool because of the increased load..

But that isn't the case at all! Apparently, the AC system NEEDS this increased airflow!
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Old 06-17-2017, 10:53 AM   #10
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Ya know, I always noticed the fans come on when the AC was running. I just assumed (I dunno why? Because I was focused on the engine, I guess?) it was to help keep the engine cool because of the increased load..

But that isn't the case at all! Apparently, the AC system NEEDS this increased airflow!
Air conditioning basics 101.

The condenser needs to be cooled to change the state of the gas back to a liquid so it can be used by the Orifice Tube (Expansion Valve). Then the liquid can expand again to a gas and cooling will happen as the process repeats.

This of course has nothing to do with the OPs problem he has indicated.
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Old 06-18-2017, 01:15 PM   #11
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Default Too make the AC do it's job it needs airflow constantly

I just fixed my son's car and it was similar. The AC worked fine while going down the road at any speed over 25. When you came to a stop the AC would make a "click" and go warm. The AC was still on but blowing barely cold air.
It turned out that the engineers put the electric fan off to one side where it would blow air directly over the Condenser. When you were driving the normal airflow was sufficient but if the fan did not come on then the car would stop cooling right after coming to a stop or crawl (which we do a lot of here in the Washington D.C. area).
The main engine cooling loop was cooled by a conventional fan mounted on the engine through a thermal clutch.
It seemed that when I heard the click it was the fan relay being activated. The fan was "dead" so the cooling system for the condenser only was compromised. I replaced the fan and cleaned the condenser and all is well again.

I have found with my 88 Coupe that an annual radiator cleaning is a way to prevent problems during the summer months. I learned this the painful way when the AC did not work so great do to about 5 pounds of leafs in the radiator shroud and between the coils. I now remove the covers and blow all the crap out of there. Then I use Coil Cleaner (made for air conditioners) and clean both the radiator and condenser coils. This may be overkill but it works for me.

If it is clean and the air has a clear path everything should work well, right?

Is there any way to test the fan motors to be sure they are in good shape?
Other than measuring the resistance of the fan motor or motor to ground connections?
If I use a current shunt I could accurately measure my power consumption but that is a pain for most people.
Any good ideas out there?

Thanks for the help! Have a Great Fathers Day!
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Old 06-18-2017, 07:44 PM   #12
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I have found with my 88 Coupe that an annual radiator cleaning is a way to prevent problems during the summer months.
Since I had a over heating related AC issue, I thought I'd take advise and do my own cleaning. AM I GLAD I DID.

The radiator was cover more than 1/2 full (see picture) of leaves, twigs and debris. No wonder the temp gauge rose in traffic and the AC could not keep within specs.

The job was straight forward about 2 hours for me (I work pretty steady and methodical, cleaning as I go) but others could do it in 90 minutes. A vacuum with a long extension is your friend.
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Old 06-18-2017, 10:11 PM   #13
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Since I had a over heating related AC issue, I thought I'd take advise and do my own cleaning. AM I GLAD I DID.

The radiator was cover more than 1/2 full (see picture) of leaves, twigs and debris. No wonder the temp gauge rose in traffic and the AC could not keep within specs.

The job was straight forward about 2 hours for me (I work pretty steady and methodical, cleaning as I go) but others could do it in 90 minutes. A vacuum with a long extension is your friend.
You did a great as many people have done with this but you're not done. There is so much debris IN the condenser and radiator (fins) you won't believe it. You can't get in there with a air hose because of the angle and tight spacing. So I made a tool to get in there. This is an cut from a thread of what I did. When you get some time and motivation you may want to do it someday.

"Quote"

I was also having the onset of a cooling problem as I could see the signs with the 90* temperatures. So I decided to also clean out the condenser and radiator. But I could not get the air hose down into the areas to blow out the junk. So I (quickly) built a right angle air hose out of a mop stick and rubber hose. Duck tape, 3 hoses, couple hose clamps and all connected to my regular air hose. It worked great as I was able to blow all 4 surfaces very clean. The temperature now does not have the tendency to creep up and it runs the coolest it ever did. I know cleaning was a huge help. Now I run below 190 with a air temp of 75 and moving.

Here is my creation to get in between both units. Removed nozzle from air trigger for needed volume of air.
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Old 06-19-2017, 02:27 PM   #14
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Default Another "Cool Tool" to Build!

That is a great idea for the "Right" tool for blowing out your fan shroud. I used the Vacuum with small extensions and lots of air pressure. I spent a while straightening out the fins on both the radiator and the condenser. It is at tight space so the blowing tool would be very useful!

Bill, that shroud fouling is the worst I have ever seen, did a creature build a home in there or something?

"Clear airflow makes for a Happy Corvette"

Thanks for the ideas!
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Old 06-19-2017, 02:51 PM   #15
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Bill, that shroud fouling is the worst I have ever seen, did a creature build a home in there or something?
Thanks! (Uh... I guess... sort of?) I'm happy to "take one for the team."

I did a radiator on my ZR1 about 3 months ago and there was not anywhere near the amount of junk between the radiator and condensor. This was pretty bad which confuses me as the car is super clean???

No, there were no creatures, just LOTS of leave, twigs and long pine needles. I often wonder what gets run over to force that stuff into and under the condenser?

I like the compressed air idea, however I put everything back together last night. I might take it our after work and see if there is a noticeable difference (and pray the AC clutch is not fried)and if not, I'll take her apart again.
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Old 06-19-2017, 03:26 PM   #16
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I too own a 1989 with A/C. One thing you might want to check it the belt tensioner on the passenger side of the engine. When we ran our car without A/C, no problems. But when we turned the A/C on, it really squealed and got a burnt rubber smell. Thought we fried the A/C compressor.

It turned out to be the belt tensioner on the passenger side. With the A/C on, it created extra tension to run. (turning the compressor) Once the tensioner was replaced, everything ran just fantastic.

Just a thougth.
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Old 06-19-2017, 04:09 PM   #17
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I too own a 1989 with A/C. One thing you might want to check it the belt tensioner on the passenger side of the engine.
Thanks for the idea- will do!
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Old 06-20-2017, 09:20 AM   #18
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**UPDATE**

I took the car out for a 30 mile cruise in the mid 80's last night. No issues at all and the temp at cruise stayed 185ish. I can tell is is a 10 cooler than before.

I drove to work this morning with ambient in the mid 70's. Again no issues and the AC was on the whole time. Temp stayed pretty steady about 195 in stop and go.

The big test will be this afternoons commute as it is supposed to be in the mid 90s.

BTW... I checked the tensioner; it is good
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