Air conditioning help

If I'm using the gauges right...car sat overnight...ambient today is only about 75F-80F. Engine/system off
Low gauge 95psi, Hi 125psi
start engine, turn on a/c...compressor is cycling again (1sec on 5 sec off it has done this before).
Low gauge cycles (between 20-30 psi) with compressor 20psi compressor kicks on-30 psi (about a second later) compressor kicks out.
High gauge hovers around 50-60psi...tube at high pressure port is COLD!

Now, after 10 minutes rest (everything shut down, engine off)...low 85+psi, high 120+psi
 
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Ran the ac with the cockpit doors closed...trying to get the compressor to cycle "normally".
Start enigine/ac: ac blows cold in car
Hi-125psi, lo-100psi tube to dryer in-warm, out-cool/cold, hi pressure valve cold
My notes say:
compressor shut off at hi-130/lo-30 dryer in-warm/out-warm
compressor on at 60psi/25psi
once at "steady state" hi stays ~60 psi, low fluctuates between 20 and 30 psi.
Funny thing is that compressor comes on for a second...lo psi drops to 20, compressor goes off...lo goes up to 30. Hi stays around 60psi.

After 5 minutes (running in my garage (75F ambient), NOW...seems to be working "normal" cockpit air is pretty cool (although drivers side is not as cold as passenger's side). Compressor is staying on (auto air set to 60F) 75-95psi/15 psi. When compressor goes off, lo climbs to about 45 psi...compressor comes on DROPS to 25. Tube into dryer amient tube out cycles from cool to cold.

It FEELS like it fixed itself...but I know Entropy theory!
 
Crap...it seems to get stuck in this mode...compressor cycling every 5 second or so...on for 1 sec, off for 4-5 sec.???
Low gauge cycles (between 20-30 psi) with compressor 20psi compressor kicks on-30 psi (about a second later) compressor kicks out.
High gauge hovers around 50-60psi...tube at high pressure port is COLD!
 
The question is what is causing the compressor to cycle, the pressure switch, the climate control unit, fan control unit or the ECU. The Freon pressure must be between 30 and 384 for the compressor to run. I would start by checking the pressure switch and see if that is dropping out.
 
Right now...most common failure mode is compressor on for 1 second off for 15seconds while high shows 60 psi...low cycles...it hits 35 psi and then compressor kicks in and low drops to 22 psi...starts to climb and then ~15 seconds later, gets to 35 and compressor bumps on and drops low back to 22psi. High pressure is really not moving?
 
Briank said:
I would back probe pin 6 (Brown\black) at the the fan control unit with a volt meter. You should see zero when the pressure switch is closed/
Click to expand...

Okay...(I'll look this up in the service manual...where is this...under dash, in console, in front compartment, etc...
Ps-the condenser fans and the blower in the dash continue to operate (its just the compressor that is cycling)...if that helps?
 
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The fan control unit is on the bulk head behind the seats, about in the upper middle. If the condenser fans are not cycling the compressor run signal is not going on and off so its either the pressure switch or the temp sensor.
 
Briank said:
The fan control unit is on the bulk head behind the seats, about in the upper middle. If the condenser fans are not cycling the compressor run signal is not going on and off so its either the pressure switch or the temp sensor.
Click to expand...

Man this group is good!
Found it (Fan control unit)...Thanks.
"pressure switch" -Are you talking about the triple pressure switch (under the front bonnet near the high pressure valve?
"temp sensor"-which one (or combination) Is there a way to test?:
Ambiant temp sensor
coolant temp sensor
sunlight sensor
Evap temp sensor
In-car temp sensor
 
TomCat said:
Man this group is good!
Found it (Fan control unit)...Thanks.
"pressure switch" -Are you talking about the triple pressure switch (under the front bonnet near the high pressure valve?
"temp sensor"-which one (or combination) Is there a way to test?:
Ambiant temp sensor
coolant temp sensor
sunlight sensor
Evap temp sensor
In-car temp sensor
Click to expand...


Yes the triple pressure switch on the high pressure line. It would be the coolant temp sensor but make sure you get the right one there are 3 one for the ECU, and one for the fan control and one for the gauge. See the service manual for locations and test procedures.
 
Briank said:
Yes the triple pressure switch on the high pressure line. It would be the coolant temp sensor but make sure you get the right one there are 3 one for the ECU, and one for the fan control and one for the gauge. See the service manual for locations and test procedures.
Click to expand...

Section 22-68 (on line manual)...but I can't tell, is that (coolant temp sensor) accessable without removing the dash...through the firewall using the remove-the-blower-fan method?
 
TomCat said:
Section 22-68 (on line manual)...but I can't tell, is that (coolant temp sensor) accessable without removing the dash...through the firewall using the remove-the-blower-fan method?
Click to expand...

That is the coolant temp sensor for the CCU you are looking for the coolant temp sensor for the fan control unit which is located on the engine.
 
Briank said:
That is the coolant temp sensor for the CCU you are looking for the coolant temp sensor for the fan control unit which is located on the engine.
Click to expand...
Brian,
I really do appreciate you spoon-feeding me...especially the electronics/sensor stuff.

I've been reading...also THANKS!
So you are saying that if the condenser fans continue to run and the compressor is droping off line it could be the engine coolant temp sensor, Page 23-113?

I guess there is just a circuit for the compressor as the car/motor seems to run perfectly (considering the temp sensor may indicate over temp).
 
TomCat said:
Brian,
I really do appreciate you spoon-feeding me...especially the electronics/sensor stuff.

I've been reading...also THANKS!
So you are saying that if the condenser fans continue to run and the compressor is droping off line it could be the engine coolant temp sensor, Page 23-113?

I guess there is just a circuit for the compressor as the car/motor seems to run perfectly (considering the temp sensor may indicate over temp).
Click to expand...

As noted above there is more then one temp. sensor. The sensor for the fan control unit is a separate and independent from the temp sensor for the ECU or the gauge. Since your compressor is cycling on and of fast I would be looking at the pressure switch first since temps don't tend to change fast.
 
Briank said:
As noted above there is more then one temp. sensor. The sensor for the fan control unit is a separate and independent from the temp sensor for the ECU or the gauge. Since your compressor is cycling on and of fast I would be looking at the pressure switch first since temps don't tend to change fast.
Click to expand...

I'm assuming that changing the pressure switch opens the system, releasing all the R134a, right...unless I evacuate the system 1st.

Also, do you have the Part #s for both tripple (sic) pressure switch and temp sensor?
 
TomCat said:
I'm assuming that changing the pressure switch opens the system, releasing all the R134a, right...unless I evacuate the system 1st.

Also, do you have the Part #s for both tripple (sic) pressure switch and temp sensor?
Click to expand...

Its unlikely the pressure switch or the temp sensor are bad so just blindly changing either is a waste of time and money. The goal here is to find out what is cycling the compressor on and off. Again as said above your backyard conversion to 134A is very suspect. You have not said the system was properly evac'ed and the proper oil put into the system. The receiver/dryer was not changed which would be done any time the system is opened or a major change made. :rolleyes:
 
Briank said:
Its unlikely the pressure switch or the temp sensor are bad so just blindly changing either is a waste of time and money. The goal here is to find out what is cycling the compressor on and off. Again as said above your backyard conversion to 134A is very suspect. You have not said the system was properly evac'ed and the proper oil put into the system. The receiver/dryer was not changed which would be done any time the system is opened or a major change made. :rolleyes:
Click to expand...

I agree, I don't want to throw $s at it and I will try to determine what is causing the cycling. I can short the BRN/BLK on the triple pressure switch. to test that.

I guess not everything was done by the book but I am sure the system was evacuated when refilled with 134a the first time...but that was years ago and it has worked until recently...and then I did the expansion valve (on Acura's analysis) and tried refilling myself...probably a mistake! But 24 hours later, I had it evacuated and restored/oiled with the right amount of 134a.

That being said, it is acting just like it did before I did the expansion valve AND when the compressor stays on, it blows cold...so I hopefully didn't destroy anything.
 
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Briank said:
As noted above there is more then one temp. sensor. The sensor for the fan control unit is a separate and independent from the temp sensor for the ECU or the gauge. Since your compressor is cycling on and of fast I would be looking at the pressure switch first since temps don't tend to change fast.
Click to expand...

I jumpered the triple pressure switch and the compressor worked as advertised...so I cleaned the contacts and re-installed the plug. The ac blew cold and with the cockpit closed up, it got to the point where the compressor was on for a period of time and off for a period of time...like it probably should (and the condenser fans go on/off periodically with the compressor). Hi PSI was 150-200+, lo was 30-50. Tube out of dryer was ambient/warm and tube at hi pressure valve was ambient/warm.

I shut it all down, waited for a few minutes and started it back up...the compressor started cycling again :(
High pressure dropped to 60psi low at 75
I jumpered the compressor again and it came/stayed on BUT I could not get the pressures to change from hi-65/lo75-80

A blockage???
 
It looks like it was the receiver/dryer...it was getting clogged up...but not all the time and not 100%.
It finally got clogged up and stayed clogged up so the symptoms stabilized.

$80 part plus a flush and re-charge and I seem to be good to go!
Thanks for bearing with me on this journey...hope it helps someone else out.

The biggest clue was that when the system was NOT working correctly, the "interface" (where hot meets cold) between the tubing/piping on the warm side (typically downstream of the compressor...the high pressure side) and the cold side (typically after the expansion valve) was not at the expansion valve BUT it was at the dryer (in was warm, out was cold).
 

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