Automotive Air Conditioning Information Forum (Archives)

Solar4 on Sun September 01, 2013 12:32 PM

Year: 2007
Make: Acura
Model: TSX
Refrigerant Type: R-134
Ambient Temp: 105
Pressure Low: 130
Pressure High: 130
Country of Origin: United States

AC has been working normal. My wife is driving home yesterday and it quit cooling rapidly. Turns out the compressor is not engaging. The electric condenser/ radiator fan engages with the AC selected ON. Same result when bypassing the pressure switch on the high side; but no compressor engagement. Compressor turns freely by hand. Hooked up gauges and the system is equalized at about 130psi. Don't know exactly how much freon is in the system but the sight glass appears normal and I feel some freon escape while hooking up gauges.

Is there another component that controls compressor cycling such as a low temp switch on the evaporator? Can you jump it to see if the compressor will engage? Is there a chance that it's the compressor/ clutch? Looking for any troubleshooting advice.

Thanks

mk378 on Sun September 01, 2013 2:10 PM

Check if power is reaching the compressor coil when it should. If not, check the fuse and relay, which are usually in a fuse box under the hood. If the compressor has power but doesn't engage, the coil may be open or the gap too wide. The controls inside the car are probably OK since the fans are starting.

Jumping stuff on a modern car tends to get expensive. Test by probing instead of jumping.

GM Tech on Sun September 01, 2013 6:04 PM

if it runs after an all night sit- and quits after engine gets warm- you probably have a too wide air gap- if so, remove a shim from in behind clutch driver...

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Solar4 on Mon September 02, 2013 12:37 AM

Quote
Originally posted by: mk378
Check if power is reaching the compressor coil when it should. If not, check the fuse and relay, which are usually in a fuse box under the hood. If the compressor has power but doesn't engage, the coil may be open or the gap too wide. The controls inside the car are probably OK since the fans are starting.

Where is the compressor coil? I am reading .091 volts on the positive lead to the compressor after the AC button is selected on. Using the same ground I read 12+ volts on both positive fan leads (ignition on car not running). Fuses were good. Pardon my ignorance, but how do I find the relay? Sounds like I might get somewhere if I could locate the compressor coil and relay!

Jag987 on Mon September 02, 2013 12:56 AM

The power lead you are getting .091 volts on, is that on the front of the compressor where the belt turns it? If so, that is the coil.

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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

Solar4 on Mon September 02, 2013 2:06 AM

Quote
Originally posted by: Jag987
The power lead you are getting .091 volts on, is that on the front of the compressor where the belt turns it? If so, that is the coil.

It is bolted onto a junction on the compressor body (where I read voltage) and then continues on to the front of the compressor. Should it read .091V or 12+V?

Jag987 on Mon September 02, 2013 6:21 AM

12+. The coil is an electric magnet that sucks the hub on the compressor in when it is activated. It is not getting enough power. What does it read when it is off? I am curious if in fact it is getting any power.

-------------------------
I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

mk378 on Mon September 02, 2013 11:33 AM

It's normal to read a few millivolts on a circuit that is "off" due to ground potential differences.

There's always a black plastic box somewhere under the hood (usually near the battery) full of fuses and relays. The car's owners manual may mention it. Typically the inside of the cover of the box is printed with a map to what each relay is for.

Edited: Mon September 02, 2013 at 11:35 AM by mk378

Solar4 on Mon September 02, 2013 3:55 PM

Ok sorry guys, scratch that .091V. That was actually the ground wire so I'm guessing residual voltage. I disconnected the power plug to the compressor and read 5.7 Volts with AC button selected on and key ignition on. With car running I read 6.3 volts. I get the same voltage readings for the power going to the pressure switch. 5.7 and 6.3 volts respectively. I have checked all the fuses and swapped around all the relays: (3 of the same and 2 of the same.)

Shouldn't I be reading system voltage (12+ and 14volts) at the pressure switch and power plug going to the compressor?

mk378 on Mon September 02, 2013 4:08 PM

You should have either near zero, or 12. Are you grounding the meter properly? Put the black probe on either the battery - post or the engine block.

Edited: Mon September 02, 2013 at 4:11 PM by mk378

Solar4 on Mon September 02, 2013 4:21 PM

Quote
Originally posted by: mk378
You should have either near zero, or 12. Are you grounding the meter properly? Put the black probe on either the battery - post or the engine block.

Yes, 5.7 Volts with AC button ON and putting black probe on either battery - post or engine mount that has large ground straps.

wptski on Mon September 02, 2013 7:29 PM

Quote
Originally posted by: Solar4


Yes, 5.7 Volts with AC button ON and putting black probe on either battery - post or engine mount that has large ground straps.
I assume that you double checked your meter right on the battery?

That very low voltage considering that the load from the clutch coil isn't even on it. Find which relay powers the clutch and if the same value/number is used in another position to swap with. If not, pull the relay and check if you have 12V coming into the relay. There should be two, one powers the relay coil and the other supplies 12V through the relay contact when closed to the clutch coil.

Solar4 on Tue September 03, 2013 1:47 AM

Quote
Originally posted by: wptski

I assume that you double checked your meter right on the battery?

That very low voltage considering that the load from the clutch coil isn't even on it. Find which relay powers the clutch and if the same value/number is used in another position to swap with. If not, pull the relay and check if you have 12V coming into the relay. There should be two, one powers the relay coil and the other supplies 12V through the relay contact when closed to the clutch coil.

Yes, the meter indicates about 12.4 battery volts. Leaving the black probe on the negative Batt post and putting the red probe on either pressure switch or compressor power plug indicates 5.7 volts. I counted 5 total relays. Two of the same and 3 of the same. I swapped all 5 relays into different positions (of same P/N) and still no compressor engagement.

Sounds like I need to check the relay source voltages.



Edited: Tue September 03, 2013 at 1:52 AM by Solar4

mk378 on Tue September 03, 2013 8:21 AM

The pressure switch is possibly a low voltage logic - level circuit. Are you sure the wire you're testing on the compressor goes to the clutch coil under the pulley? If you unplug the compressor you should measure 3 or 4 ohms through its coil circuit to ground.

Solar4 on Wed September 04, 2013 1:05 AM

Quote
Originally posted by: mk378
The pressure switch is possibly a low voltage logic - level circuit. Are you sure the wire you're testing on the compressor goes to the clutch coil under the pulley? If you unplug the compressor you should measure 3 or 4 ohms through its coil circuit to ground.

Well I can't seem to upload a picture from my device to the thread. The link below is a picture of the compressor's plug. It has three wires. Let's call em #1, #2 & #3 in order from left to right. I cannot get continuity among any single one of the three and ground. The only combination that resulted in continuity was by attaching a meter probe to #1 and the other meter probe to #3. This resulted in 0.2 ohms.

Compressor Plug

Edited: Wed September 04, 2013 at 1:10 AM by Solar4

mk378 on Wed September 04, 2013 8:06 AM

The center pin (yellow wire?) appears to go to the clutch coil. It should have continuity to ground.

The other two are a thermal switch that should be normally closed between the two but no continuity to ground.

wptski on Wed September 04, 2013 8:17 AM

Quote
Originally posted by: mk378
The center pin (yellow wire?) appears to go to the clutch coil. It should have continuity to ground.

The other two are a thermal switch that should be normally closed between the two but no continuity to ground.
If the center wire goes to the clutch coil and the other two are a thermal switch, where's the ground wire at?

mk378 on Wed September 04, 2013 9:45 AM

One of your pictures of new compressors has a green wire coming out of the clutch coil, that wire goes to a bolt which grounds it to the compressor frame. So the coil circuit should return to ground through the engine.

Solar4 on Wed September 04, 2013 9:55 AM

Quote
Originally posted by: mk378
One of your pictures of new compressors has a green wire coming out of the clutch coil, that wire goes to a bolt which grounds it to the compressor frame. So the coil circuit should return to ground through the engine.

Ok, so the coil is open/ bad. Compressor is original- 6 years old and 81,000 miles. Guess I should replace the whole thing? Clutch and compressor?

wptski on Wed September 04, 2013 11:35 AM

With the plug remove, on the compressor two of three contacts should read 3-4 ohms, if not the coil is open. The only problem is what about the 5.7V that you are reading, something isn't right.

mk378 on Wed September 04, 2013 1:22 PM

The thermal switch circuit is logic voltages like the pressure switch, in fact it is likely just in series with the pressure switch.

Compressor unplugged, center wire on compressor plug to compressor frame should be 3-4 ohms. Outer 2 wires near zero ohms to each other but open circuit to ground.

wptski on Wed September 04, 2013 2:47 PM

Quote
Originally posted by: mk378
The thermal switch circuit is logic voltages like the pressure switch, in fact it is likely just in series with the pressure switch.

Compressor unplugged, center wire on compressor plug to compressor frame should be 3-4 ohms. Outer 2 wires near zero ohms to each other but open circuit to ground.
The OP never read 12V on anything yet as far as I know. One end of the coil is grounded internally? Didn't think they still did such things.

Solar4 on Thu September 05, 2013 2:05 AM

First off, I want to thank everyone for their input, suggestions and most importantly patience with me! Thanks to you, The problem has been narrowed down to the coil circuit - it's open. Unfortunately the compressor is at the bottom and I will have to remove power steering pump or at least alternator just to make sure it is indeed the coil versus bad power or ground wiring. Haven't had much time other than a few minutes of troubleshooting a day. Once again, I appreciate everyone's help but I gotta give an extra shoutout to mk378! You 'da man!... Or woman if applicable...

The compressor thermal switch is in series with the high pressure switch. Makes sense: high temp and/or high press, shut it off! Verified by continuity of one wire from press switch plug to a compressor plug outer wire. I also noticed that the electric condenser fans would not run unless both the press switch and compressor plugs were connected (closed series circuit). Therefore, I had to jump the compressor plug outer 2 wires (simulating a closed thermal switch) and have the car running to FINALLY read 13.8 Volts on the Center wire of the same compressor plug! The 5.7 volts must indeed be a low voltage logic as mk stated. Seems like it took me forever but I was finally able to prove that the compressor coil (at the plug anyways) is receiving 13.8 Volts+/- of juice when the car is running. Who needs schematics and wiring diagrams?? HA!

So my next question is, (didn't think I was done did ya??) am I gonna have to open the system and replace the the whole compressor and clutch assy? Or can you buy just coils anywhere? The compressor isn't that new but it's been blowing ice cold air down in our 100+ degree weather and I hate to mess with that if I don't have to.... not to mention the cost difference


Edited: Thu September 05, 2013 at 2:10 AM by Solar4

wptski on Thu September 05, 2013 7:53 AM

It depends on the type of compressor and its location. Some clutch plate require a puller so you need room to use that. Same goes for the pulley, a bigger puller yet that you need room to use and a snap ring to remove first. The coil is pressed on but can be removed using a large screw driver prying back/forth.

To put everything back means room for a hammer, etc.