SOLVED. PART 2...A/C light blinking mystery (1 Viewer)
- Thread starter BullElk
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I doubt the static pressure is high enough for this test at his location now. I used this switch to wire an electric fan on my 80 before. The static pressure didn't turn on the fan often when the vehicle is not driven, even in hot summer with 100F+.
That's because the circuit for the fan requires 220 psi before it comes on and it will run until pressure lowers to approximately 170 psi.
So we would hope it did not come on without the AC running.
So ambient temp (or a radiant influence) would need to be 137°F for it to come on (AC system off) and then not dip below 120°F (cut off) for it to continue to run on. I suppose some places Arizona in direct sunlight this might be possible.
Static pressure to satisfy the low pressure side of the trinary switch would be about 50 psi (less actually...but that is the standard most techs use). So the OP needs an ambient of about 54°F to achieve that. This is with respect to the clutch operation, has nothing to do with the Condenser Fan or an AUX Fan added.
^^^^
This is exactly right. When the coolant temp reaches approximately 227-230°F the ECU will disable the compressor. When temps fall back down to aprox. 217-220°F it will come back on. A faulty temp sensor might cause it to cut out almost immediately. So that IS a possibility. And this folks is why chasing down A/C issues not directly related to a refrigerant charge is so fun.
That's because the circuit for the fan requires 220 psi before it comes on and it will run until pressure lowers to approximately 170 psi.
So we would hope it did not come on without the AC running.
So ambient temp (or a radiant influence) would need to be 137°F for it to come on (AC system off) and then not dip below 120°F (cut off) for it to continue to run on. I suppose some places Arizona in direct sunlight this might be possible.
Static pressure to satisfy the low pressure side of the trinary switch would be about 50 psi (less actually...but that is the standard most techs use). So the OP needs an ambient of about 54°F to achieve that. This is with respect to the clutch operation, has nothing to do with the Condenser Fan or an AUX Fan added.
My logic was faulty. I was thinking high pressure test.
I don't really know. The only way I could feature that would be IF the sensor still works BUT has failed such that it signaling a high temp right from the start.
If the sensor were not working at all.....I can't say.....but it doesn't seem logical the engineers would shut down the AC over one redundant sensor.
Yes, see what you were getting at now.
No...the high pressure side (if switch is working correctly and we don't know that) would involve extremely high pressure (in excess of 455 psi).
I've never seen pressures that high in an automotive AC system.
I used the back end of a jeep to mostly destroy that sensor a long time ago. I don't remember the AC not working for the 5 hour drive home.
If I was closer and not so busy waiting on fed ex deliveries I'd drive over a gauge set.
If you want me to check anything on a new denso compressor, as in compare readings, I have a new one in a box here. (same denso part number, all years)
I don't think that one sensor, or the two inside would lock out the compressor, just maybe keep the AC light flashing.
definitely coolant temp sensor and maybe the evaporator's sensors.
But looking at techstream would give you that info if it was bad. I doubt there is any other external ambient temp sensor but the one.
If I was closer and not so busy waiting on fed ex deliveries I'd drive over a gauge set.
If you want me to check anything on a new denso compressor, as in compare readings, I have a new one in a box here. (same denso part number, all years)
I don't think that one sensor, or the two inside would lock out the compressor, just maybe keep the AC light flashing.
definitely coolant temp sensor and maybe the evaporator's sensors.
But looking at techstream would give you that info if it was bad. I doubt there is any other external ambient temp sensor but the one.
I agree, I don't 'think' a coolant temp sensor (if completely non functioning) or the thermistor on the evap would shut down the compressor.
As for ambient temp sensor, yes there is only one....also a cabin air temp sensor, but again.....these shouldn't prevent the compressor from running.
Make sure connection to the compressor is fully seated. Mine was loose and caused the blinking light but worked sporadicall.
BullElk
SILVER Star
- Thread starter
- #72
I just checked. Connection to compressor is fully seated. It will be a few days before I delve back into the A/C fun due to cold rainy weather.
While I wait, I do have a techstream cable but need to find a cheap laptop or whatever else is needed to set it up. Maybe it will help.
While I wait, I do have a techstream cable but need to find a cheap laptop or whatever else is needed to set it up. Maybe it will help.
Yes, cheap LapTop with Windows XP or 7 installed. Some versions are compatible with later model Systems (windows 10).
Having a source to read diagnostic codes and 'real time' parameters can be an immense help. So at the very least....a GOOD scanner or something like techstream will be your friend.
Being one of the Dinosaurs here....I am not as computer savvy as some....so I opted to use a dedicated scanner but anything that lets you look deeper into the workings of the systems is helpful.
Battery connections. If there is any corrosion or even oxidation on either of the terminals, or a bad ground, the tiny voltage difference from the speed relay on the compressor will make the ECU think the AC clutch is not turning at the same speed as the engine and it will disconnect. It doesn't take much of a voltage differential, because it disconects the clutch very quickly to keep a bad compressor from eating the serpentine belt. Spend time with a wire brush making the posts and terminals shiny, and the brass connector to the main fuse block nice and shiny. Then crank the battery terminals down TIGHT. That fixed my flashing light issue.
BullElk
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- Thread starter
- #75
As mentioned before, when the compressor was jumped at relay location when charging with freon, the engine seemed to really be dragging at a low rpm more than other properly working systems. Seems like that could be a redish colored flag to those smarter than I.
You can still bypass the 'Lock Out Sensor' by disconnecting and jumping the two terminals. IF the system works from that move alone....then its pretty clear you have a compressor issue or a faulty sensor (take your pick).
That would also eliminate the pressure switch.
IF it didn't cause the compressor to run...then I would jump the pressure switch (Lock Out still jumped) which would then prove out the possibility of the pressure switch being bad. Kill two birds with one stone. IF still no compressor action then you're pretty much looking at wiring/connectors or the Center ECU...is the way I see it.
BullElk
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- Thread starter
- #77
As @flintknapper suggested (as he has unselfishly done for several days now) I uplugged the connector to the A/C compressor to get an Ohms reading to determine if sensor was bad. Sensor was not bad but when I plugged the connector back in the A/C is now working with no blinking light. It appears the issue was possible light corrosion on prongs perhaps but so far it works perfectly.
Thanks to all for all the assistance in trying to resolve this issue. I now know a few land cruiser loads of information more than I did a few days ago. I can't wait til someone says they have a blinking A/C light.
@LXstalker, you suggested the connector not being seated properly. If I had taken it off instead of just pushing it in this would have been over 24 hours ago. You were right on track. Thanks.
Thanks to all for all the assistance in trying to resolve this issue. I now know a few land cruiser loads of information more than I did a few days ago. I can't wait til someone says they have a blinking A/C light.
@LXstalker, you suggested the connector not being seated properly. If I had taken it off instead of just pushing it in this would have been over 24 hours ago. You were right on track. Thanks.
ramangain
Clarksonian disciple
Three Land Cruiser owners - one from Alabama, one from deep East Texas, one from North Carolina - walk into a bar ....
You did fine. You worked on it diligently where others might have quit.
When diagnosing A/C issues (that aren't refrigerant related) it can get pretty involved. LOTS of possibilities to work through.
Even IF the solution ends up being a simple one.....it doesn't mean that 'finding it' will be so simple.
DTC's (Diagnostic Trouble Codes) are often helpful in pointing you in a direction, BUT they can also take you WAY off on tangents that end up being a waste of time. In the end....'familiarity' with the components involved and the application of simple logic are more valuable.
Patience and perseverance are good virtues to have when working out electrical problems. And I don't see where you could be faulted there.
Good Job.
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