AC Relay and Compressor troubleshooting

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Stella87
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AC Relay and Compressor troubleshooting

Postby Stella87 » Thu May 24, 2018 7:00 pm

Hi guys, I read through the l300 ac wiring thread in the technical library, but am having a difficult time understanding and trouble shooting the system. I cannot find the ac compressor relay as pictured in the thread. Ive had my delica for almost 2 years now and finally just got the ac charged. I took it to a shop, and although it took awhile to cool down it was working... I was SO stoked as i live in arizona. Well right after i had that done, one of the roller bearings on the rocker arms broke so the van sat for around 2 weeks while the parts came in. I just finished installing a new rocker arm and adjusted the valves, and now the ac compressor is not engaging. no click from the relay, no engine rpm change, nothing (side note, is there supposed to be a light behind the AC switch?). I dont know where to begin even after having grazed through that thread i mentioned. The + from the compressor is plugged in, and the thermo switch is plugged in by the coolant hose. i unplugged and replugged in the big relay behind the glove box... is the big one right center behind the glove box the relay for the AC compressor or is it a different one?
Where the heck is this?
ac compressor relay.jpg
ac compressor relay.jpg (64.62 KiB) Viewed 358 times

I would reallllly appreciate a more simple walk through of where to check first. TIA
"Delilah" 91 L300 P35W Exceed

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Growlerbearnz
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AC Relay and Compressor troubleshooting

Postby Growlerbearnz » Thu May 24, 2018 10:44 pm

Whoops. The AC workshop manual mentioned in that thread is for a different vehicle (the Pajero) and isn't entirely correct for our engines. I think I mentioned that in passing, but I've gone back and made it more clear. The correct L300 AC manual has since been found- you'll need to download the entire workshop manual from here: http://www.delica.ca/forum/viewtopic.php?f=17&t=17809

Troubleshooting: easy things first.
-Check the fusible links in the battery compartment- one of them runs the entire AC compressor system, independently of the heater/fans. If the AC fusible link is broken the heater fan will still work, you just won't get any AC.
-Try applying 12V directly to the compressor clutch wire (unplug it from the loom first). If the AC clutch goes "clunk" then it's working.

All the AC electrical bits (relays, secondary fuses, timer/control module) are mounted behind the glove box, which you'll need to remove. The first thing to check would be the 3 glass fuses clipped to the front of the evaporator box- they're in white plastic holders. Above those, at the top of the evap. box, are the AC relays. Below the fuses is the AC timer relay- it's a black box, but on mine the label says "AC timer". That box delays AC engagement by a few seconds to prevent the compressor from "chattering" (between 5 and 20 seconds, by my reckoning, depending on its own internal logic, which I haven't entirely figured out yet). The full throttle switch, for example, causes the timer to turn off the AC for about 10 seconds.

The AC switch has a light in it, but it's only for night time illumination. It's usually green, but there's a flap of yellow filter in the switch which makes the AC lettering glow yellow when it's turned on. If the headlights are on. Basically, you can't tell if the AC switch is good by looking at its light.
Nothing says "poor workmanship" more than wrinkles in the duct tape.

Stella87
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Location: Flagstaff, Arizona

AC Relay and Compressor troubleshooting

Postby Stella87 » Fri May 25, 2018 5:34 am

Will check that first thing this morning and get back. Thanks a lot!
"Delilah" 91 L300 P35W Exceed

Stella87
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Location: Flagstaff, Arizona

AC Relay and Compressor troubleshooting

Postby Stella87 » Fri May 25, 2018 6:52 am

12BCFB2B-7409-4F6D-9301-2F05F6EEDBFA.jpeg
12BCFB2B-7409-4F6D-9301-2F05F6EEDBFA.jpeg (111.46 KiB) Viewed 342 times

Again apologies for my incompetence but where is the fusible link in this? Not working with much room here with my dual batteries!
"Delilah" 91 L300 P35W Exceed

Stella87
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Location: Flagstaff, Arizona

AC Relay and Compressor troubleshooting

Postby Stella87 » Fri May 25, 2018 6:55 am

I jumped the compressor and the magnetic clutch is working and held it there long enough to verify that ac is cooling :x
"Delilah" 91 L300 P35W Exceed

sk66
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AC Relay and Compressor troubleshooting

Postby sk66 » Fri May 25, 2018 7:10 am

Stella87 wrote:Again apologies for my incompetence but where is the fusible link in this? Not working with much room here with my dual batteries!

I think it should be the green one in the lower left of the picture.
Steven
1991 L300
Harrisburg, PA

Stella87
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AC Relay and Compressor troubleshooting

Postby Stella87 » Fri May 25, 2018 8:50 am

Just left the shop, my pressure had dropped significantly. Does the dual pressure switch keep the compressor from engaging if the refrigerant pressure is low? I’m an idiot for installing a used compressor, Butch had one lying around at CVI that he gave me, I should have sent it in as a core for a remanufactured one but I Was trying to save some cash :-( lesson learned
"Delilah" 91 L300 P35W Exceed

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Growlerbearnz
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AC Relay and Compressor troubleshooting

Postby Growlerbearnz » Fri May 25, 2018 2:34 pm

So it's working now? :-)

Stella87 wrote:Does the dual pressure switch keep the compressor from engaging if the refrigerant pressure is low?

Yes. The pressure switch will not allow the AC to engage if the pressure is too high *or* too low, to prevent damaging the compressor.

If the pressure's dropped, I would think you have a leak somewhere. Did the shop put some UV leak-tracing dye in the system? If they did, find yourself a UV flashlight and go around the AC system looking for a glow where it's leaking.
Nothing says "poor workmanship" more than wrinkles in the duct tape.

Stella87
Posts: 40
Joined: Sun Dec 25, 2016 10:07 am
Member's Photo Album: http://www.delica.ca/Photos/
Vehicle: Mitsubishi Delica L300 P35W
Location: Flagstaff, Arizona

AC Relay and Compressor troubleshooting

Postby Stella87 » Wed Jun 06, 2018 1:11 pm

You know its strange when I left he said no leaks, but it obviously was leaking somewhere. I had it refilled and he still said it didn't look to be leaking. Could it be a product of heat expansion or something while im on the road but not at stand still? Is there more pressure on the system when in motion? just a thought. GrowlerbearNZ thanks as always for the help. Was going to start a new thread about troubleshooting an intermittent working rear blower, so looking forward to your advice on that.
"Delilah" 91 L300 P35W Exceed

sk66
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AC Relay and Compressor troubleshooting

Postby sk66 » Wed Jun 06, 2018 1:54 pm

I don't think there's anything relative to being in motion vs at a standstill. If pressure dropped too low for the compressor to engage there has to be a leak somewhere...
Steven
1991 L300
Harrisburg, PA

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Growlerbearnz
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AC Relay and Compressor troubleshooting

Postby Growlerbearnz » Wed Jun 06, 2018 3:27 pm

Stella87 wrote:...when I left he said no leaks...


Pretty sure he didn't check *everything*. Getting at the evaporators isn't easy, you kind of have to remove the dashboard and most of the AC ducts. The rear one's not easy either. If the front condenser (under the bumper on the left) has taken a rock it might be leaking slowly from the core- same with the main condenser in front of the radiator.

I would find out if he put UV dye in the system (and get him to do so if not), buy yourself an LED UV flashlight, and start pointing it at AC pipes, junctions, and components, until you find something glowing. If you're lucky it might be an O-ring at some junction, which is easy to replace.
Nothing says "poor workmanship" more than wrinkles in the duct tape.


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