AC Jumper?

[Sundowner]

Okay, forgive me for not finding it posted somewhere, but I've been searching and not finding: how is the bypass jumper wire installed in the switch circuitry on a variable-load AC system? I know I've seen it discussed, but I can't find a diagram for it and I can't find my electrical schematic .

I'm pretty sure that the control box is actually working correctly, because I can hear a relay engaging when I move the load control dial...but the compressor isn't kicking on, so if there's something amiss it's on the downstream side. I figured that if I can bypass the box, I'll be able to start troubleshooting.

 

[TreadingLight]

Are you confident the system is charged? The pressure switch might not be closing.

You can find schematics for most 70 series at cruisercult.com.

 

[Sundowner]

Actually, no... I'm not confident in that at all. I'm confident in the other direction; I know it needs at least a bit of refrigerant. Hadn't even considered that, to be honest.

I know I have some R-134a laying around, but I've always added refrigerant with the compressor running...which is what it's currently not doing. No idea why I've done it that way; someone probably told me to a long time ago and I've never thought about it.

 

[jblueridge]

I think the signal (or its absence) from the pressure switch is evaluated in the little box and if all is well the relay closes.
You can run power direct to the compressor’s clutch to test it.
I had mine running that way for 2 summers.

 

[Sundowner]

Okay, so here's a better question: in order to fix the low-refrigerant problem and eliminate that part of things, can I just untangle the compressor circuit, manually engage it, run a pile of R-134a into it, and then see where we get?

 

[jblueridge]

That’s what I would do,
but that is not the same as telling you it’s the right thing to do.

 

[Sundowner]

That’s what I would do,
but that is not the same as telling you it’s the right thing to do.

Well, here's what I found on the compressor....

 

[TreadingLight]

If you apply 12v to that connector the magnetic clutch on the compressor will engage and it will start spinning. Assuming your clutch is good, which it probably is. I wouldn't do that for long though, since you don't know if the system is charged (and thus lubricated). It would be useful only to tell you if the clutch is working.

Since I am not an AC expert I would do this by the book and go through the troubleshooting section from the manual.

When you get to the point of charging the system, you can either do it with the engine off (adding liquid refrigerant on the high side) or with the engine on (adding refrigerant vapor on the low side).

You can get gauges pretty cheap on amazon or at harbor freight, assuming those vendors are available in the virgo supercluster.

The Toyota manual is very thorough.

This is from the rm3626e covering early 70 series.

 

[Sundowner]

If you apply 12v to that connector the magnetic clutch on the compressor will engage and it will start spinning. Assuming your clutch is good, which it probably is. I wouldn't do that for long though, since you don't know if the system is charged (and this lubricated). It would be useful only to tell you if the clutch is working.

Well, 24v, but yeah, that's what I expected it to do. Thing is...that little red wire isn't a factory wire. It doesn't feel good at all - like, kinda janky inside - and it's been spliced...so something has gone wrong here before.

Since I am not an AC expert I would do this by the book and go through the troubleshooting section from the manual.

When you get to the point of charging the system, you can either do it with the engine off (adding liquid refrigerant on the high side) or with the engine on (adding refrigerant vapor on the low side).

I have a small quick-connect dingus that I use on the low side ports. I connected it this morning and it was showing 70-ish PSI, but who knows if that's accurate.

You can get gauges pretty cheap on amazon or at harbor freight, assuming those vendors are available in the virgo supercluster.

Might be a Hobo Fright thing, or possibly just a rental, for as infrequently as I'd use them.

The Toyota manual is very thorough.

Problem is, I'm very inept.

I managed to grab a copy of the wiring diagram; it located one of the AC relays directly adjacent to the controller box behind the glove compartment; I can hear that one engaging, so I know something is happy enough to tell it to work ...but if there's another circuit somewhere that's cutting power to the clutch, then it makes sense that it's still not working.

 

[AirheadNut]

I would remove the jumper wire and return things to stock, then proceed with diagnosis. It is pretty easy to check the pressure switch for continuity (should be closed circuit with the engine off) and also check for 24v at the compressor. Run a jumper from the battery to the magnet clutch plug to test for proper clutch engagement, you can do it with the engine off (listen for the clutch to engage) or with the engine on (watch for the clutch to start spinning). If both those things check out then your problem is further upstream in the AC control system.

 

[Sundowner]

I would remove the jumper wire and return things to stock, then proceed with diagnosis.

Well, I don't know if the red wire is a jumper or a replacement wire or something else; I just know it isn't a stock Toyota wire.

It is pretty easy to check the pressure switch for continuity (should be closed circuit with the engine off)

Gotta find the pressure switch, first; I was looking for where it should be and haven't come up with it yet...but it was also dark and rainy at the time, so that might have had something to do with it. Gonna jump back in here in a bit.

and also check for 24v at the compressor. Run a jumper from the battery to the magnet clutch plug to test for proper clutch engagement, you can do it with the engine off (listen for the clutch to engage) or with the engine on (watch for the clutch to start spinning).

That's basically what I was going to do; unplug that connector, clip a lead on the battery and touch the other end to the connector pin, and see if anything clicks or spins.

If both those things check out then your problem is further upstream in the AC control system.

I really wish I was better at troubleshooting; even when I try to be systematic, I always get overwhelmed and confused and forget to start with the fuses.

 

[Sundowner]

AC clutch works when jumped to the battery, and there's actually a bit of refrigerant still in the system: maybe 10 to 12 PSI. Unfortunately my little AC-filling dingus isn't doing anything more than reading the working pressure because the only can of R-134a that I have is dysfunctional...so I have to rectify that before I can go much further.