dead battery, now no A/C (Air Conditioning) - Jeep Commander Forums: Jeep Commander Forum
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post #1 of 6 (permalink) Old 07-13-2014, 06:24 PM Thread Starter
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dead battery, now no A/C (Air Conditioning)

Hey y'all:
I sure hope some of y'all can shed some light on this for me.
I have an '06 Commander with 64k miles on it. I'm the second-owner and I've owned it for 4 months, and 15k miles.

I've been noticing that the A/C was getting "sporadic" lately. It's HOT around here right now (most days over 100d), so minor differences in AC performance are noticeable.

Today I ran a short errand (less than 3 minutes driving) and when I came back out 30 minutes later car was dead. Some quick checks showed a dead battery, so I hooked the battery charger to it and immediately noticed a relay clicking under the hood. It turned-out to be the AC Clutch Relay. I removed it and then left the charger on the battery for a couple of hours.

When I went back out to the JEEP, I checked the voltage and had 12.98v. I inserted the key in the ignition and all sorts of weird things happened, like the lights in the dash flashing, the windshield wipers running, etc etc. when I tried to crank the motor, everything quit, and the battery voltage dropped to 4v. Classic bad-battery stuff.

So I replaced the battery with an Optima, and then I put the relay back in the AC Clutch Relay socket. Started the JEEP back up and everything returned to normal.... EXCEPT:
Now I've got ZERO A/C. The clutch doesn't engage, and the relay doesn't seem to be kicking when I switch the A/C to "ON" with all the controls set to HIGH. (Dual Auto Climate)

Has anyone experienced anything like this?
Can you steer me in a direction?

thanks.
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post #2 of 6 (permalink) Old 07-14-2014, 12:08 AM
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Sounds like the relay failed and damaged your battery. (or it was coincident the battery went out the same time as the relay)

New battery fixed everything but the failed relay that was the root of the problem, thus no ac.

Have tried swapping out the AC relay with another relay, see if the AC works and what ever you swap the AC relay into stops working? If so, then a new relay is your answer.

BTW, vehicles with computer control, with multiple computers communicating on a network to activate things, a bad battery typically does cause the random activation and reactions that you got.


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Last edited by Mongo; 07-14-2014 at 12:10 AM.
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post #3 of 6 (permalink) Old 07-14-2014, 08:30 AM Thread Starter
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Thanks Mongo, I had the same thought last night, so I ran to Orileys and picked-up a new relay. No change. Still doesn't kick.
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post #4 of 6 (permalink) Old 07-14-2014, 09:07 AM
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If refrigerant pressure is too low or too high, the compressor will turn off/NOT turn on.

Since you're saying the AC never turns on, then its possible its too low, i.e. if you had a refrigerant leak, once the pressure got low enough the AC would never start. Of course if you turn it on, and wait a minute or two before checking, its possible it turned on and pressure went to high and it automatically shut down, of course it would cycle on/off if that was the case and if left it running and watched it long enough you would have seen it cycle on.

The fan is turned on by the AC system hi side pressure going to a certain pressure, that tells the system its warm enough that it needs the fan to cool it. If the fan doesn't turn on (bad relay/fan) the pressure will continue to climb until the system shuts it down to prevent damage. In most vehicles on a warm day, with the car sitting still, the fan will turn on within seconds of turning the AC on. Some vehicles just turn the fan on anytime you turn the AC on.

You need to put a gauges on it and find out the pressures.

If you don't have a set of proper gauges, but have one of those cheapo low side gauges for just adding a little, you could do a simple check with that. If the AC has been off for more than 1/2 hour, the pressures will equalize throughout the system, i.e. its the same at both ports. Most car ac systems, when off on a warm day (80F) the static pressure in the system should be around 100psi, if its at 25psi or less, the AC system won't even turn itself on. Which would mean you have an AC leak.


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post #5 of 6 (permalink) Old 07-16-2014, 07:49 AM Thread Starter
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Thanks for your help, guys.
Strange thing: it started working again on my commute home monday.

So I made an appointment at my dealer to bring it in and have it checked-out, thinking it probably needed a charge. But yesterday when I took it in, they told me that pressure is correct, and the outlet temperature is within parameters, and that they do not recommend I do anything with it.

I dunno. I guess I'm shrugging my shoulders a little bit? and scratching my head.
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post #6 of 6 (permalink) Old 07-16-2014, 09:29 AM
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First, if you have an AC problem, any good AC shop is probably better than the dealer for working on your AC problems.

Second, it might have been a stuck thermal expansion valve or electrical relay, that has come unstuck and will continue to function normally, so you might have just had a glitch.

If it comes back, then you have something intermittent. If it starts functioning normally again, and tests normal, then its likely the only thing that could fail intermittently on an AC system. You can't be losing refrigerant and oil if the system is passing the test with gauges, so don't add regrigerant or oil, until a real test shows you've lost it, you'll just mess up the system.

I'm no expert, but to the best of my knowledge, the only thing that could fail intermittently.

The only moving parts "inside" an AC system are the pump and expansion valve. The pump being driven by the motor, if it fails it will almost always chew itself up and thus NOT come back to life and function normally again. So, that just leaves the expansion valve. (sure you can argue pressure relief valves, but you'd lose all your refrigerant if the pressure relief valve failed).

*Thermal Expansion Valve intermittently sticks.
*AC clutch intermittently fails to engage. (the solenoid/coil is the only thing I could think would be intermittent in that) the rest would give obvious signs.
*Relay to power the AC clutch.
*Relay to power the AC fan.
*Pressure Sensor for the AC.

I've had a bad pressure switch on another vehicle that caused the AC to intermittently fail, if would fail to turn turn on the fan sometimes, and at low speeds or a stop, the AC pressure would build so high and make the pump so hard to turn, the engine would stall at idle. Then the pressure switch would start working normal again, and no one could figure out the problem.

The commander has a single pressure sensor in the AC and a temperature sensor at the evaporators. A computer uses readings from those sensors to decide how to control the AC, an erronous reading from one of the sensors could cause the computer to conclude the wrong thing and thus the AC won't work, until the sensor sends the right info.

I'm NOT sure on the relays, I "believe" there is at least one relay to power the clutch to the pump. Relays are notorious for failing intermittently. Thus you clutch won't turn on.

The relay for the fan (it might be a solid state relay, i.e. a big transistor pack that if it fails at all it would burn out and NOT work again) if the fan does NOT turn on when it should, like slow speeds and stopped, the AC pressures will build too high (often in seconds) and the computer will shut off the AC.

Finally, the solenoid/coil for the AC clutch. The relay sends power to the Coil in the clutch, which is a big electromagnet that engages the clutch and starts the pump turning. If that solenoid/coil fails, it will NOT engage the clutch and thus no AC. Solenoids/coils are big windings of lightly coated wire (for insulation) encased in plastic/rubber/silicone to seal it up, it is NOT uncommon for these to become compromised and it causes them to fail intermittently. I.e. if they get wet they fail until they dry out, too much humidity in the air can cause them to fail, they have minor internal shorts and just temperature will effect the short, i.e. if they get too hot or cold they fail, but work if they stay at another temperature, etc, etc.

A good AC shop would have checked things that could cuase intermittent failures, like test the relays, the pressure sensors, solenoid/coil and test the thermal expansion valve. Granted, if its intermittent, they might pass the test at that moment with flying colors, but a part that shows something off spec, like resistance, they would replace it and hope that eliminates the problem.

A dealership will just put the gauges on it and check the readings against the book and tell you there is nothing wrong, please pay your bill now.

I had a car that sat for 4 months, the AC didn't work when I fired it up again, the gauges showed it wasn't flowing correctly but properly charged. I tried again in an hour, the 2nd time I engaged the AC after sitting for months and everything worked perfectly. My guess, the thermal expansion valve stuck from sitting so long, once it started moving, it worked fine again.


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