SOLVED. PART 2...A/C light blinking mystery (1 Viewer)

[BullElk]

2000 LX. A/C light blinks after compressor engages for about three seconds then disengages.

What I DO know so far...... thanks to the generosity, knowledge and guidance of @flintknapper is......

--The compressor will engage fine when jumping the relay.
--The relay is good (tested in other vehicle)
--Front A/C amplifier is good (tested with known good source)
--Rear A/C amplifier is good (tested with known good source)
--Pressure switch is good
--Freon has been evacuated, filled properly and tested with no leaks

Anything else you guys may have run into or anything else to check that comes to mind ??

Thanks a bunch.

 

[ramangain]

What's the pressure on the low side?

 

[medtro]

Clutch or seize compressor? It could be compressor turns slower than engine.

 

[flintknapper]

Clutch or seize compressor? It could be compressor turns slower than engine.

This would activate the compressor 'lock out' sensor and prevent the clutch from engaging alright, but in an earlier test the OP jumped the unit and states it runs fine. We had discussed that when trying to sort this out via PM, but ultimately decided it would be best to bring the issue to the general forum in hopes of soliciting a solution.

I'm not intimately familiar with the circuit (from relay to clutch) but I would think if he can jump it from that point that the Lock Out is probably not the issue, but not 100% sure of that.

IF the sensor detects a significant difference between engine speed and compressor speed, it assumes the compressor is trying to seize. So in an effort to save the serpentine belt from shredding, it disables the clutch.

 

[BullElk]

What's the pressure on the low side?

Don’t remember what it was and I don’t have real gauges.

 

[ramangain]

Well, it worked before vacuum and refill right? Instinct leads me to believe you may have a pressure delta before and after, preventing operation like it did previously.

 

[flintknapper]

Well, it worked before vacuum and refill right? Instinct leads me to believe you may have a pressure delta before and after, preventing operation like it did previously.

No.

OP recently acquired the vehicle and believes it has been sitting for quite some time.

At various times diagnosing this....it has shown A/C codes 21,47 and 00 in that order.

OP originally attempted to add refrigerant and then later took it to an indy that recovered 38 ozs. Indy indicates 'no leaks'.

It's possible the Binary switch (high/low) pressure switch is faulty but I don't remember exactly the point at which he 'jumped' the circuit.

OP states when jumped the system does cool, it just won't initiate clutch engagement from the controls and he has a blinking light. Or possibly it does engage but immediately kicks out.

Jumping the clutch and putting a set of gauges on it would eliminate any pressure related reasons for the his issues, but I suspect its electrical.

 

[ramangain]

Ah, I thought this was maintenance of one of the many in his (taxi) fleet. My bad!

 

[BullElk]

Or possibly it does engage but immediately kicks out.

Yes it does engage for like 2-3 seconds when pressing ac button. And it would stay on when filling with freon myself. But would not stay on long. That’s why I originally thought it was just leaking out.

 

[medtro]

This would activate the compressor 'lock out' sensor and prevent the clutch from engaging alright, but in an earlier test the OP jumped the unit and states it runs fine. We had discussed that when trying to sort this out via PM, but ultimately decided it would be best to bring the issue to the general forum in hopes of soliciting a solution.

I'm not intimately familiar with the circuit (from relay to clutch) but I would think if he can jump it from that point that the Lock Out is probably not the issue, but not 100% sure of that.

IF the sensor detects a significant difference between engine speed and compressor speed, it assumes the compressor is trying to seize. So in an effort to save the serpentine belt from shredding, it disables the clutch.

It runs with jumping the clutch proves the clutch is not completely dead, but difference in speeds may still exists. I would remove serpentine belt to check if clutch and compressor can be spin freely.

 

[BullElk]

I just removed belt and compressor and clutch moves freely. Clutch not as fast as compressor however.

 

[flintknapper]

I just removed belt and compressor and clutch moves freely. Clutch not as fast as compressor however.

You are saying the clutch 'pulley' spins freely and the compressor (when turned by hand by the clutch) offers some resistance (as it should)?

The clutch pulley when spun by hand should turn pretty freely (actually spin several times around). The compressor (connected to the A/C clutch) should NOT spin at all...but you should be able to turn it by hand with some amount of resistance because the system is closed and charged.

So we need a clear accounting of what you found.

 

[medtro]

Not too many things left since you tested the relay, amplifiers and pressure sensor already. Diagnostic info in the first thread below.

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[BullElk]

With belt tension loosened, I can spin the compressor pulley (where belt rides) freely by hand . The disengaged clutch in front of that will spin about 2 inches. And both spin indepedant and separately of each other of course. And that is exactly the same action as on my '04 with working A/C.

 

[BullElk]

FYI.....the condensor fan does work. It did come on when filling back up with freon by indy. Maybe that will confirm the pressure switch in fact works. I am just wondering what action would take place by compressor with a bad pressure switch. Would it run longer than 3 seconds before cutting off and at more inconsistent amounts of time before cutting off? Currently, the compressor engages and disengages in the same exact 3ish seconds.

If I remember this correctly, the only time when the light has stayed on longer than the common 3 seconds after pressing button was when actually filling with freon. But then, when full, and press A/C button it would not stay on.

And during the measly three seconds the compressor does run, the low pressure lines are cold as I would expect with a working system.

 

[flintknapper]

With belt tension loosened, I can spin the compressor pulley (where belt rides) freely by hand . The disengaged clutch in front of that will spin about 2 inches. And both spin indepedant and separately of each other of course. And that is exactly the same action as on my '04 with working A/C.

That is correct for both components. Exactly what I would expect.

 

[flintknapper]

FYI.....the condensor fan does work. It did come on when filling back up with freon by indy. Maybe that will confirm the pressure switch in fact works. I am just wondering what action would take place by compressor with a bad pressure switch. Would it run longer than 3 seconds before cutting off and at more inconsistent amounts of time before cutting off? Currently, the compressor engages and disengages in the same exact 3ish seconds.

If I remember this correctly, the only time when the light has stayed on longer than the common 3 seconds after pressing button was when actually filling with freon. But then, when full, and press A/C button it would not stay on.

And during the measly three seconds the compressor does run, the low pressure lines are cold as I would expect with a working system.

The condenser fan IS tied into the Trinary Switch and switches it on and off at specified pressures. So that would tend to suggest that the pressure switch is working in that mode anyway (mid pressure). It would not eliminate the possibility that the high pressure side of it was not acting up.

It would seem to confirm that the low pressure mode was being satisfied....as the compressor clutch will engage initially, but once pressure builds the high pressure mode 'could' be cutting it off. Normally this wouldn't happen until you have 400+ psi pressure, but a faulty pressure switch might have it cutting out earlier. Unfortunately....to replace it, you have to evacuate the system of refrigerant.

One other possibility is the 'Lock Out' sensor on the compressor. IF you have an aftermarket compressor on the vehicle it has been documented here that the sensors on 'most' are unreliable and have caused hours and hours of troubleshooting efforts only to find it was the problem.

So...if you can get your phone down there (in the Abyss they place compressor) and snap a pic to see if you have an OEM compressor....that might tell us something. Isn't diagnosing A/C issues fun....?

 

[BullElk]

I will try to do that. Not terribly fun but like most issues with these vehicles, they’re a once in a lifetime fun event.

 

[BullElk]

Denso it is. I should have went ahead and replaced my timing belt while I was in there.

 

[flintknapper]

Good !

I guess at this juncture.....I'd be wanting to see a set of gauges on it, system jumpered and get some High/Low side pressures.

Clear any AC Codes first and then check to see afterward if any new ones appeared.