No HVAC After Jump Start

[Shuttlesworth]

Alright Gurus both A/C and Jeep. I have a tricky one. I helped a buddy at work jump off his car and my A/C completely stopped working. A little history....

I recently replaced the accessory belt. Some starts depending on the weather the belt would start to chirp, so to stop that I would turn off A/C until the everything warmed up. This went on for a few weeks (I never really got around to adjusting it). Fast-forward to the event in question. It was after work and I was heading home and said buddy needed a jump (old battery). So I pulled around and helped him out. We got everything hooked up and I started the Jeep up (it may have already been on, I can't remember) and the belt started chirping. So, in keeping with what I had always done, I turned the A/C off and the chirp stopped. We waited while the battery charged and he got his car started. After disconnecting everything and I was about to pull away, I turned on my A/C. NOTHING.... No fan, no compressor, no RPM dip, nothing.

I have poked around the fuses and all are still working fine. Nothing I could tell is out of the ordinary. Now, I am pretty mechanically inclined, but A/C and Electrical is something I haven't even "novice-d" yet, let alone mastered. And now we circle around to my original problem.

I have no A/C after a jump start and I can't figure out what needs to be fixed. I planned on replacing all of the A/C equipment as it is a bit old (268K), but I am looking to get some quick fix before I dive into that, just to get me by until I can get all the components to replace.

PS: There is no heat as well (obviously) But things are starting to get chilly where I am. Please help, I'm so cold...

 

[qslim]

Okay, so for clarification after you jumpstarted your pal's truck you're HVAC system entirely stopped working.

When you have AC selected on the knob does your compressor still work? Is the clutch spinning or still?

 

[Shuttlesworth]

I haven't looked to see if the clutch is engaged, but when I select the A/C section on the switch I can't hear it engage. I usually hear it and see a dip/rise in RPM. Also I have no fan at any level. I was getting 1-3 but not 4 ( I know how to fix that, hence replacing most A/C components mentioned in OP)

I have switch all knobs to all configurations and have gotten no results. I am going to lunch now, and I will check the clutch engagement.

 

[pagrey]

PS: There is no heat as well (obviously) But things are starting to get chilly where I am. Please help, I'm so cold...

This is pretty important, are you saying the fan doesn't run? I don't see how heat and air are connected other than the blower fan and that's probably something simple like the control switch.

 

[qslim]

Check fuse 8 (10A) in the fuse block behind the glovebox and fuse 11 (40A) in the PDC under the hood.

I was getting 1-3 but not 4 ( I know how to fix that, hence replacing most A/C components mentioned in OP)

How were you planning on fixing that?

 

[Shuttlesworth]

This is pretty important, are you saying the fan doesn't run? I don't see how heat and air are connected other than the blower fan and that's probably something simple like the control switch.

I say obviously since I said there was no fan in the original post. Everything linked to HVAC went out. Maybe the title should read HVAC instead of just A/C

 

[Shuttlesworth]

Check fuse 8 (10A) in the fuse block behind the glovebox and fuse 11 (40A) in the PDC under the hood.

How were you planning on fixing that?

New switch and replacing blower motor. The common issues with the switch is too much current running through it, due to the windings in the blower motor shorting. I checked fuse 8, but I didn't know that 40A fuse was for A/C as well. I didn't have the service manual with me at the time. Let me go check, I got a few more minutes on break.

 

[Shuttlesworth]

New switch and replacing blower motor. The common issues with the switch is too much current running through it, due to the windings in the blower motor shorting. I checked fuse 8, but I didn't know that 40A fuse was for A/C as well. I didn't have the service manual with me at the time. Let me go check, I got a few more minutes on break.

Just check said fuses, all are intact. I even switched the relay to make sure that wasn't the issue and again it is working just fine.

 

[pagrey]

All good, I just can't read. The chirp is probably because the tensioner is old, it does need to be replaced at some point. The extra load is just causing the belt to slip. Still I have a feeling the switch panel, blower resistor and fan motor are probably all contributing to the problem. Sometimes you can just remove the fan and rotate it a few degrees and it'll work again until it stops on the dead segment again. I don't think jump starting did anything but who knows? The resistors aren't too bad to swap. Short term I might inspect the switch panel to make sure it hasn't melted, replace the resistor and see if you can get the fan spinning. The A/C is probably just not getting signal to turn on from the panel. Sorry if this is obvious, it does sound like you know what you're doing.

 

[Shuttlesworth]

All good, I just can't read. The chirp is probably because the tensioner is old, it does need to be replaced at some point. The extra load is just causing the belt to slip. Still I have a feeling the switch panel, blower resistor and fan motor are probably all contributing to the problem. Sometimes you can just remove the fan and rotate it a few degrees and it'll work again until it stops on the dead segment again. I don't think jump starting did anything but who knows? The resistors aren't too bad to swap. Short term I might inspect the switch panel to make sure it hasn't melted, replace the resistor and see if you can get the fan spinning. The A/C is probably just not getting signal to turn on from the panel. Sorry if this is obvious, it does sound like you know what you're doing.

I will try that this weekend. But I doubt the A/C is down to the switch. I can hear the vacuum lines clearing once I change its position to another space. I have also replaced the resistor before so that shouldn't be the issue, but I will check that as well.

 

[qslim]

I will try that this weekend. But I doubt the A/C is down to the switch. I can hear the vacuum lines clearing once I change its position to another space. I have also replaced the resistor before so that shouldn't be the issue, but I will check that as well.

The position blend door is purely vacuum control, so the fact that you hear vacuum doesn't speak to the integrity of the switch from an electrical perspective. The switch provides path to ground for both the blower and the A/C input request to the PCM. Looking through your wiring diagram it's the only component I see in common.

 

[Shuttlesworth]

The position blend door is purely vacuum control, so the fact that you hear vacuum doesn't speak to the integrity of the switch from an electrical perspective. The switch provides path to ground for both the blower and the A/C input request to the PCM. Looking through your wiring diagram it's the only component I see in common.

Ok, I will give that a check this weekend. I am close to ordering an entire switch cluster (fan selector is burnt out and I cracked the plastic last time I replaced it).

 

[qslim]

Here's a snip from your manual. You can trace the flow down from the PDC fuse # 40, through the blower motor relay, through the blower motor, into the fan speed switch, through the A/C heater control switch and then to ground. Also the fact that you said the highest blower setting doesn't work is odd, and that's another symptom of a bad switch vs. a resistor pack. When the resistor pack goes bad you ONLY have the highest setting because that's the only position that doesn't use the resistors.

On this page you can see how the A/C select input function from the PCM flows down through the A/C heater control switch & goes to the same ground as the blower.