Theory 101 A/C Compressor Defunct causes Lurching

[snowwind1990]

I could be way off with my theory so here seems the best place to test it out.
I have had a nightmare regarding the near stall to total stall on Bart.
1. thought it was fuel pump failure
2. replaced fuel pump
3. replaced CID
4. replaced TPS
no codes
5. we have a very loud squeal of belt from alternator pretty constant, occurred simultaneous to the ongoing drama.
didn't think about it as a possible cause.
Knew the compressor was defunct, didn't engage it other than for heat or defrost over the last two years.
Went to have an A/C guy check out what it would take to get it back in running condition.,.....he informed me that no power was getting to the A/C clutch and he didn't know why? he wouldn't let me near Bart while he was inspecting it....
Don't know exactly what he did.....or did not do...
Best Conclusion:Maybe this could cause the lurching and stall: the compressor belt is locking up and causing the alternator belt to not turn and that causes the sudden loss of power and the tach goes to '0' and the drive pulley is frozen up and even if you stomp on the gas you get no release of the squeeling belt, you get not power either.

Just clutching at straws here....whatdoyouthink?

 

[Rob94]

I'm not sure exactly how to decipher what you have just asked, but I can pretty much guarantee that the engine would/should have more than sufficient power to overcome a frozen pulley. The pulley wouldn't turn, the belt would. In effect, the belt would heat up, smoke like crazy, and eventually break as a result. If the compressor clutch won't engage, it could be low/out of refrigerant, the clutch could be worn to the point that it needs replacing or regapping.

 

[rangerj]

MaMaM,

Here are a couple of thoughts for you.

If the A/C clutch will not engage;
1. the clutch gap has worn to a point where it is too wide to be drawn together. the gap should be about .035, but should work up through about .050.

2. the low pressure switch may be bad. you can attach a jumper wire from one connection to the other in the switch connector. That should activate the clutch if the switch is the problem,

3. The clutch coil could be bad. You can apply battery voltage to the clutch coil, where the wires connect to the coil, and it should become a powerful magnet,

4. The relay for the clutch coil is in the CCRM. Dig up the thread from the Utah or Colorado Sho club regarding testing the A/C electrical system, it is a realy good thread, pictures and all (Thanks guys),

5. A pressure test of the system will tell you if the low pressure is the cause of the "low pressure switch" not being activated. YThat is what the switch is there for!

6. The drop in RPM and/or stalling could be caused by a compressor that is gummed up and about to sieze. You can remove the A/C / alternator belt and check for free movement of the A/C pulley and the alternator pulley, and the tensioner pulley. You can put a socket (13mm I think) on the A/c shaft nut and see if the compressor turns freely (clockwise only).

The compressor should not take more than about 7 ft. lbs. of torque to turn, however this is when the compressor if out of the car (it is a "work bench" test). So, if the compressor is "hooked up" it should take more effort to turn it but not more than say 10 lbs of torque. Just put a socket on it and see if it turns without an "unreasonable" amout of resistance.

Try these things and see if we can go from theory to reality! If not of this works get back to us.

One more thing, if your mechanic could not figure out why the clutch would not engage, find another mechanic. Living where you do with all that heat there should be an A/C mechanic on every corner. rangerj

 

[snowwind1990]

compressor turns freely, so does the clutch

however, the clutch switch has been disconnected.....does that matter or not?

Should make this point clear.....I don't care if I have A/C or not, I am trying to find out if a belt that is squeeling (possibly from a failing compressor/clutch) would cause the lurching problem and the drop in rpms that has been the problem for a couple of weeks now.

 

[snowwind1990]

The Clutch Gap

Well I'm not sure what it should be.......all I know of the history is the shim was removed by Sergio Perfetti with the full agreement of the original owner. Sergio doesn't remember doing it or why it would have had to be done.....but says that if he did do it, the original owner knew he did it....
That didn't exactly leave me with a full understanding, because the original owner says he did not have any clue why the shim was removed...
no know no.
So.................here we are 3 years later and I suspect problems with the A/C compressor and clutch as culprits in the dropping rpms, stall drama.

Well, we put everything back like it was and we are no further along than before in solving the "drama of the dropping rps and stall"....poor, poor Bart.

 

[Rob94]

Bad throttle positioning sensor?

 

[snowwind1990]

No.....TPS was replaced

and the TPS was good.

We have finished for the night.....after Kenneth took Bart apart again and put him all back together.....the evil one ran fairly well...although, two things still don't seem right..
1. behind the DIS nestled next to the fuel reg is a connector (gray) with another little connector, single wire that fits into a black receptacle...well after we were done for the night, I was still curious and started touching and pulling on things and found it loose. actually, it fell out of the black holder and it was corroded...don't have a clue yet what it is.
and.,.....
the weird thing we found out : the squeeeeeeeling can be stopped dead in its tracks, just remove the neg. battery cable while car running, hook it back up and squeeeeeeel returns......
Now wtf is that all about........
Well, maybe we can call it a night..I would drive Bart now, but not far..at least the rps seem to hold up better...I really don't think we have solved any problem, we just adjusted a lot of things and changed the symptoms on one sick SHO from Hells black waters...but knowing the history of Bart, he has had problems since he was bought, was towed back to the dealer the first day. According to the records, his first incident of lurching and bucking was when he was 13 days old and again when he was just over 3 months old...
good night for now....but we will return with more drama from the "evil one".

Manufacture date: Bart: Aug. 27, 1990

 

[NoFlipping]

Could the sqealing be the alternator? Possibly in combination with a battery that it just can't charge fully? Battery might have a short that's putting a strain on the alternator. Just a thought. Good luck with Bart.

 

[Bizzy]

MaMaM...I stumbled on this topic rather late, but I've been searching through my books ever since to see if there was anything I could do to help. Going right to the source (my car) was also quite helpful.

I think you hare having 2 separate issues here, one that you've basically found by looking/jiggling the wires.

The wire/connector you speak of goes to your cam sensor. If this was loose, it would explain the tach going to zero and I would imagine the stalling or stumbling as well I'd think. My car never ran very well when this sensor was on it's way out.

Pics....on the car and then off the car .... take a look and tell me if this is what you're seeing.

The squealing issue I think is perhaps the compressor freezing up enough perhaps just enough to make the belt talk to you. If you take the belt off, check that the alternator is turning freely, the compressor and while you're there check the tension pulley.....anything that that belt makes contact with...to make sure that they turn freely. If you find something stuck, or hard to turn, then it'll be pretty easy to narrow down.

It could also be that the belt was too loose? Maybe it just needs to be tightened up to take some of the slack out. Have you read the battery voltage across the terminals? You might also consider having the alternator checked. It could be that it's not charging to full capacity (one of the diodes may be blown) and it's still charging, just not enough.

Just thoughts for you to ponder.....

 

[DHMag]

an A/C compressor ready to seize WILL rob performance. from experience: the swash plate dislodged a bearing and jambed the piston onto the swash plate, causing total lockup. in turn, this froze up the swash plate shaft, which is connected to the clutch pulley. as this happened, the belt squealed very loudly and put enough strain on the engine to **** it while at WOT at 7K RPMs.

 

[rangerj]

Ah Biz, don't you mean crankshaft position sensor?

MaMaM,

The squeeling could be a belt or a bearing. The alternator bearing make a whole lot of noise when they go. The negative battery cable trick makes me think you might have an aternotor problem. If the A/C compressor turns freely, and the clutch pulley turns freely, how about the alternator pulley?

Does the tensioner pulley turn freely? Tis a puzzlement! rangerj

 

[Bizzy]

Yessir, I did. My fingers were going faster than my brain as usual.