[Waffles]

Hello friends, I'm coming to you from Baja where about two weeks ago our AC stopped blowing cold. It wasn't much of a concern until recently as it's been getting hot driving across the desert and we will have a several day trek back to the US soon where it will also be hot!

I've been in full research mode as we live in this thing full time with 3 dogs (yes we're crazy) and their comfort is my main concern. First step was checking the compressor clutch which was not engaging. I've checked fuses, all are OK. I attempted to jump the low pressure plug as mentioned here on the forums and that was a no go. Finally, today, I jumped the AC Enable Relay and the clutch engaged and beautiful cold air blew into the cab! I checked the freon level with a very basic gauge and it's in the green.

I'm not much of a mechanic, I know enough to be dangerous and keep us hopefully rolling down the road. My question to you all is, would this be as simple as replacing the relay, or is there something else I should be looking at? I have access to an auto zone about 40 min away where I'm hoping they will have the relay. But I've also seen people on this forum report replacing this relay and it not fixing the problem. I'm camped out with friends for a few more days so I have time to poke around some more if yall have any ideas.

Also question #2 , is it safe to leave the relay jumped while driving so we can have cool air or is this not safe? The last thing I want to do is create a more expensive problem.

Sorry forgot to mention this is a 2005 cargo, no rear AC.

 

[bryancraftyhands]

My extent of knowledge on a vehicle AC system is limited, but I will offer what I can.
The low pressure switch you jumped is to turn off the AC system when it determines low pressure in the system. The idea is that if there is low pressure in the system, there must be a leak, and the oil in the system must also be gone, so if it were to continue to run without the oil, the compressor would seize. If the compressor seizes, you break a belt, and you don't go anywhere.
You jumped that and the system still didn't turn on, and you checked with a gauge and show in the green, so that should be good.
The AC enable relay, could very much be your culprit. If you turn on your defrosters, does you compressor cycle on and off intermittently? It should.
If you turn to full AC, it should stay on.
If it is not turning on for either, then that would be a good bet.
In theory, the jumping the relay should be no problem so long as you have proper pressure in a good sealed system. You have a direct drive fan, so you don't have to worry about a secondary electric fan turning on. This would basically be like running "max AC".
If you need your defrosters, this isn't practical though.

 

[highfigh]

Hello friends, I'm coming to you from Baja where about two weeks ago our AC stopped blowing cold. It wasn't much of a concern until recently as it's been getting hot driving across the desert and we will have a several day trek back to the US soon where it will also be hot!

I've been in full research mode as we live in this thing full time with 3 dogs (yes we're crazy) and their comfort is my main concern. First step was checking the compressor clutch which was not engaging. I've checked fuses, all are OK. I attempted to jump the low pressure plug as mentioned here on the forums and that was a no go. Finally, today, I jumped the AC Enable Relay and the clutch engaged and beautiful cold air blew into the cab! I checked the freon level with a very basic gauge and it's in the green.

I'm not much of a mechanic, I know enough to be dangerous and keep us hopefully rolling down the road. My question to you all is, would this be as simple as replacing the relay, or is there something else I should be looking at? I have access to an auto zone about 40 min away where I'm hoping they will have the relay. But I've also seen people on this forum report replacing this relay and it not fixing the problem. I'm camped out with friends for a few more days so I have time to poke around some more if yall have any ideas.

Also question #2 , is it safe to leave the relay jumped while driving so we can have cool air or is this not safe? The last thing I want to do is create a more expensive problem.

Sorry forgot to mention this is a 2005 cargo, no rear AC.

It's a PITA, but it would be a good idea to check the high pressure switch, especially if it starts to blow the fuse whenever you try to use any of the AC modes, including defrost. Mine had a shorted HP switch and when I used a meter to check continuity, I had that across both pins AND from either pin to the block. I inserted a paperclip in the plug and covered it- worked like a charm, but that switch is necessary, for long-term survival of the compressor.

If you bypassed the Low Pressure switch and got it to work, you can use the heater controls to turn it on and off, but replace it ASAP.

 

[ehbrown1]

Assuming that the control switch is working and all fuses are good, next in line is the low pressure switch. If you jump this out - NEVER jump this one out for very long. If the system is low on refrigerant, the soluble oil which is mixed with the refrigerant during operation won't find its way back to the compressor and that's bad news. The other reason for not jumping it out is because when the correct amount of refrigerant is in a given system, there is a certain amount of subcooling involved which is basically the low temp suction line refrigerant returning to the compressor also keeps it cool. That's why you have condensation on the accumulator with a properly operating system. If you are low on refrigerant, there is no subcooling and the compressor won't like it for very long.

Next in line is the high pressure switch, which is handy during fan failure, overcharging or contaminants in the system restricting flow, as it keeps the refrigerant IN the system and prevents vision costly blowouts.

That signal passes to the Vehicle Control Module for AC enable. That signal goes to the AC enable relay under the hood.

Three fuses make it all work, the 20A HTR-A/C fuse #12 (under dash) for the control switch and the 12 volts to the selector switches, the 10A IGN-E mini fuse H7(under hood) which supplies current during IGN ON condition, and the 10A A/C Comp mini fuse K11(under hood) which is the switched voltage feed for the relay. That's really all there is to it.

If you jump the A/C relay and the air works, then either the relay is bad, a wire is loose or the VCM is holding out the A/C enable for another reason.

The easiest way to diagnose the relay is to switch it out with the relay in the rear of the fuse box. That's the headlamp relay and if that relay works for you then you just solved your problem. Just make certain the relays are in the correct way as they are easily reversed and don't work well that way.

 

[Waffles]

Thank you everyone for the feedback. We made it to auto zone and sadly the relay did not work so I'm back to the drawing board.

Here's where we're at:

I checked both the defroster and max ac and the compressor does not cycle for either. Literally the only way I can get the compressor to cycle on is by jumping the AC Enable Relay. Not the AC Relay, and not the low pressure switch.

Fuses all check out. I will need to wait until we get to our next camp to check the high pressure switch.

At this point I'm at a loss and not sure what to look for next. I do have some freon and the gauge is on the lower end of the green so I may try adding some more unless you all feel that would be worthless.

I may just end up seeking a mechanic in La Paz at the end of the week.

 

[ehbrown1]

If the low pressure switch is not open then adding refrigerant will change nothing. It never hurts to buy a cheap set of gauges and see what's really happening while the system is running. The Vehicle Control Module is holding the AC from running. I've attached a wiring diagram so you can test wiring individually. The signal from the selector/control goes thru the low pressure switch, then the high pressure switch and finally to the VCM. If the VCM is in a good mood, it enables the AC Enable relay to bring the compressor on. If both switches are OK then the wiring or the VCM has a problem. If you have access to a Tehc 2 tool then you can narrow the problem down even further. If not, then the old fashioned voltage tester will work too.

 

[Rod's Trucks]

Assuming that the control switch is working and all fuses are good, next in line is the low pressure switch. If you jump this out - NEVER jump this one out for very long. If the system is low on refrigerant, the soluble oil which is mixed with the refrigerant during operation won't find its way back to the compressor and that's bad news. The other reason for not jumping it out is because when the correct amount of refrigerant is in a given system, there is a certain amount of subcooling involved which is basically the low temp suction line refrigerant returning to the compressor also keeps it cool. That's why you have condensation on the accumulator with a properly operating system. If you are low on refrigerant, there is no subcooling and the compressor won't like it for very long.

Next in line is the high pressure switch, which is handy during fan failure, overcharging or contaminants in the system restricting flow, as it keeps the refrigerant IN the system and prevents vision costly blowouts.

That signal passes to the Vehicle Control Module for AC enable. That signal goes to the AC enable relay under the hood.

Three fuses make it all work, the 20A HTR-A/C fuse #12 (under dash) for the control switch and the 12 volts to the selector switches, the 10A IGN-E mini fuse H7(under hood) which supplies current during IGN ON condition, and the 10A A/C Comp mini fuse K11(under hood) which is the switched voltage feed for the relay. That's really all there is to it.

If you jump the A/C relay and the air works, then either the relay is bad, a wire is loose or the VCM is holding out the A/C enable for another reason.

The easiest way to diagnose the relay is to switch it out with the relay in the rear of the fuse box. That's the headlamp relay and if that relay works for you then you just solved your problem. Just make certain the relays are in the correct way as they are easily reversed and don't work well that way.

An excellent description of the system. Thank you.
Rod J

 

[bryancraftyhands]

If you jump your AC enable relay, and change the switch in the dashboard from AC to anything else, does it respond accordingly? Could your dashboard switch be malfunctioning?

 

[AstroWill]

Fuses all check out. I will need to wait until we get to our next camp to check the high pressure switch.

Did you check them all, or just the ones related to the A/C compressor. Visual check only or with a meter? Have you looked at the wiring diagrams?

Info Share - Owners/Service/Parts Manuals - Wiring Diagrams

Got any good info ? schematics ? wiring diagrams ? trouble shooting charts ? links to informational webpages ? pictures ? upload them here! feel free to upload anything you want and put it where ever you want or wherever you can. also you can download the info from this website ...

www.astrosafari.com

 

[AstroWill]

If the low pressure switch is not open then adding refrigerant will change nothing. It never hurts to buy a cheap set of gauges and see what's really happening while the system is running. The Vehicle Control Module is holding the AC from running. I've attached a wiring diagram so you can test wiring individually. The signal from the selector/control goes thru the low pressure switch, then the high pressure switch and finally to the VCM. If the VCM is in a good mood, it enables the AC Enable relay to bring the compressor on. If both switches are OK then the wiring or the VCM has a problem. If you have access to a Tehc 2 tool then you can narrow the problem down even further. If not, then the old fashioned voltage tester will work too.

That wiring diagram would be incorrect for how his van is wired.

 

[Waffles]

If you jump your AC enable relay, and change the switch in the dashboard from AC to anything else, does it respond accordingly? Could your dashboard switch be malfunctioning?

Yes every responds as normal! Yesterday was errand day and we ran it with the relay jumped all over town and 45 mins out to the beach. Max AC/AC/off, low to high and cold to hot all working fine.

Did you check them all, or just the ones related to the A/C compressor. Visual check only or with a meter? Have you looked at the wiring diagrams?

Info Share - Owners/Service/Parts Manuals - Wiring Diagrams

Got any good info ? schematics ? wiring diagrams ? trouble shooting charts ? links to informational webpages ? pictures ? upload them here! feel free to upload anything you want and put it where ever you want or wherever you can. also you can download the info from this website ...

www.astrosafari.com

We checked them with a meter but I'll admit we've only looked at the AC related fuses.


I'm camped with someone who sells industrial compressors for a living and he thinks it's the high pressure switch. Is there an easy way to test for it, like jumping it or just putting a meter on it?