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Dodgerench
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3385
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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We have a 2001 Dodge Durango. Lately we have been having

Customer Question

We have a 2001 Dodge Durango . Lately we have been having different issues going on.
The A/C won't work, turn it off and back on it works. Last night after coming home the car would not unlock the back doors. Then this morning the headlights came on when my husband started the car and he can't get them to turn off. Is this a wiring problem? or a computer issue?
Submitted: 1 year ago.
Category: Dodge
Expert:  Dodgerench replied 1 year ago.

Goood morning, welcome to JustAnswer!.

Your A/C problem can have a number of causes and will require some investigating to find out which one (or ones) are responsible.

To begin with, the A/C compressor request signal is sent directly from the HvAC control head via a hard wire to the PCM (not a bus signal), depending what the evaporator temperature is. Once a signal arrives at the PCM (engine controller), the PCM will need to look at other inputs such as refrigerant pressure, engine speed and time-since-start to determine whether it really wants to energize the A/C compressor clutch relay.

It's a chain of events that stops the process at any point where a link breaks, so...

The HVAC head may have problems with the switch, logic or hard-wiring to the PCM.

The evaporator fin temperature sensor may be showing an unrealistically cold state, which wouldn't normally require compressor engagement (to prevent freeze-up). An already-cold evaporator doesn't need compressor engagement, but the fin temperature sensor might not be accurate. Either way... no compressor for you.

You have to have refrigerant pressure in the Goldilocks Zone -- neither too high nor too low -- before the PCM will command the compressor to come on. Pressures that are too low suggest a leak in the system which could cause compressor damage and high pressures suggest that the system is already pressurized or overfilled. Engaging the compressor at pressures over 450 psi would be a bad idea either way, so conventional logic would be to leave the compressor off at that point. The actual problem would be more likely that the A/C pressure transducer is lying its butt off than that you have an actual over-pressure situation at first request unless the system had been recently worked on and severely overcharged with refrigerant.

If OK to this point, the PCM will wait a period of time consistent with its programming to allow the engine to settle after a startup event, which can take up to 30 seconds.

Once the start delay (or engine speed delay if RPMs aren't correct), the PCM will ground the control circuit for the compressor clutch relay, hopefully sending power to the compressor clutch. Relays are basically magnetically-controlled switches, so this simple task may also fail at times.

Now, if power actually gets sent to the clutch coil, the air gap that separates the friction surfaces of the clutch must be narrow enough to allow available magnetism to pull the clutch shut, engaging the compressor itself (the end product). Clutches wear with use, gradually increasing this air gap, so you may have issues with attaining engagement intermittently, especially with a hot engine.

So, there are a number of places where your A/C can fail and it'll take some digging to find where the problem is. My expectations would be with the A/C pressure transducer (located in the liquid line) and an excessive air gap on the clutch. Lightly tapping on the clutch with a hammer when the compressor refuses to engage will normally cause it to snap to attention as a quick-n-easy test.

Power door locks have two control circuits: One for just the driver's door and another that's split between the rest of the door locks. If you lost the rear doors, you almost had to have lost the RF and liftgate locks as well, but may have gone unnoticed. If you had control of the driver's door lock, but intermittently lose the others, it strongly suggests there is a problem with the Central Timer Module (CTM), which leads us to the headlight problem, which is almost certainly CTM-related.

The CTM has its fingers in a lot of places on your Durango, with the odd exception of compressor operation. Almost all lighting, front wiper delay, theft, rear wiper operation, rear defrost, horn, key-in chime and 4x4 transfer case operation depend on this one module, located in the left kick panel (left of the e-brake). CTMs do have a history of throwing an occasional fit that may be corrected with a quick battery disconnect, but they're likely to do it again at that point.

I'd suggest unplugging the CTM itself first, to preserve trouble codes in other systems if you need to have them scanned later. To reach the CTM, first yank the door opening sill plate off by pulling straight up against its mounting clips. Then remove the two Phillips screws that secure the left kick panel to the body; one in the sill trough and one far-forward and high. The black plastic box with 3 connectors now exposed is your CTM. Disconnect all three connectors, wait 10 seconds and reconnect. The dome lights should come on now (in case they weren't operational previously) and headlights should be off.

If effective in restoring anything that didn't work previously, it does implicate the CTM, meaning you're going to need one sooner or later. Besides the power lock and headlights on problems, there may have been other systems involved, but these two are likely to go together.

Replacement is simple for the CTM, but none of your key fobs will work until programmed by the dealer or a repair facility. I can't recommend using a salvage CTM either, as they can carry undesirable features from the donor unit to yours, immobilizing it by causing theft activation (especially if your Durango doesn't have theft). CTMs come in three variations depending on accessory build differences, so you'll need to take your VIN to the parts counter at the local Dodge store for proper matchup. Expect it to cost between $350 to $500, plus a half-hour of shop time to program the fobs (another $60).

I'll stop there for now to let you get caught up. Let me know if you have any questions and I'll be happy to help.

Good luck!

Ed

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