Resurrecting Early Overhead A/C?

[Gauche1968]

Finally, some photos. I tested the relays under the dash today. The one on the right in the photo is resposible for the blower fan operation. I was able to test all three existing relays by swaping in a know good fourth relay and moving each existing relay to this position. Fans operated with each relay. So, at least in that function they are all good. Still, there is no power on the wire to the compressor: engine running or not; with either the fan switch or the temperature switch in the on position.
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1984 Vanagon GL
1984 Vanagon Westy

[djkeev]

You may find this thread helpful, or the many links within this thread......
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Stop Dead Photo Links how to post photos

Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[Gauche1968]

[djkeev]

[Gauche1968]

[jlrftype7]

Saturday is meant to be dry. I'll take our Vanagon apart and trace the power output wire from the Compressor backwards to the A/C controls/Fusebox and report back in the late afternoon. Tonight is supposed to be very wet, so no go for working out in the Street with our Parked Vanagon...
Although, has Vanis13 already done this while overhauling and updating their A/C system? Just wondering.
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'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto

[Gauche1968]

[vanis13]

[jlrftype7]

[xflyer]

These 'add-on' aftermarket AC systems are usually all electro-mechanical. As someone described it, the temp control knob changes the tension on a spring. The spring is push-pulled by the pressure of a diaphragm. One side of the diaphragm has refrigerant on it that travels through a tube that has its end in the evaporator. As the temp of the evaporator changes, that changes the pressure in the tube and at the diaphragm. When the temp knob is rotated clockwise ("colder") the spring tension is changed and the switch contacts will engage sending power to the compressor clutch.
The electrical part is a 'series' circuit. If the fan switch is "OFF" no power goes anywhere. Switch the evap fans to any "ON" speed and power goes to the fan motors and the temp control. If the system has not been running for a minute or more, no matter where the temp control is set, the evap is likely warm enough to engage the switch in the temp control and the compressor should engage.
What looks like the sense tube for the temp control is in one of the photos near the black plastic piece. It is coiled up and would be long enough to go back through the overhead duct and be inserted into the evap fins.
There could be a low pressure switch somewhere. Usually the switch is on the filter drier. It could be anywhere in the refrigerant lines. Just need a fitting for it to screw into.
Need to trace the wiring with a test light or voltmeter.
BTW many of these aftermarket systems from VPC (Volkswagen Products Corp) or DPD had wiring that was all black insulation. Much harder to trouble shoot/trace.
Which leads me to think that the red wire going to the compressor clutch was a later repair or add on.
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1989 Campmobile, 1984 7 passenger beater Vanagon
Both with cool A/C

[Gauche1968]

I had a chance to do some wire tracing yesterday, which involved peeling back a lot of 40 year old electrical tape:

There are three wires coming from the evaporator housing area into the driver's wheel well: a small gauge green wire, a similar gauge red with black stripe and a larger gauge black with red stripe. These three then run together with the small gauge solid red wire coming from the compressor in the wheel well.

These four wires meet up with two solid red wires coming directly from the hot post on the battery. One is a heavier gauge than the other. All six wires then run concurrently up to the front of the van then into the dash where they travel various paths to the two spade fuses or the three relays.

The two red wires coming from the battery terminate in the spade fuse holders. I measured voltage here and there is only 9.6 volts at both holders, compared to 12.2. volts on the solid red wires at the battery box.

That is as far as I have gotten.
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1984 Vanagon GL
1984 Vanagon Westy

[Gauche1968]

A little more progress today: I verified the solid red wire to the compressor is good, by applying 12V directly from the battery at the end that terminates at the relay connector under the dash and I got 12V back at the compressor, so thankfully no need to run a new wire there. Also, the two red wires directly from the battery to the relays are providing battery voltage to the two relays they connect to through the spade fuses, when using a good ground for the multimeter.

I still have no voltage at the relay connector that contains the compressor wire under any condition. This connector contains the compressor wire, a ground, a red and blue wire to the radiator fan wiring and a red and black wire, which I assume is the one that travels back to evaporator housing. I am able to get 12v to this connector, by jumpeing the red and black wire from the neighboring relay to the red and blue wire at the connector to the radiator fan wiring and turning the evaporator fans on, but this does not trigger the relay to send voltage to the compressor wire.

Which post on the 5 pin relay generally carries voltage into the relay? Is there one that is usually the signal post?
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1984 Vanagon GL
1984 Vanagon Westy

[jlrftype7]

[Gauche1968]

Here is how that relay I am having trouble with is wired: Pin 87 is not used, Pin 87a is the compressor wire. Pin 30 is the red and black wire from evap housing (I am assuming this from the fan or temp switch), pin 85 is ground and pin 86 is the red and blue wire to the radiator fan. There is no source of constant 12 volt power. The red and blue wire runs to a two pin connector to the rad fan where it meets the red and black wire from the neighboring relay, which provides power to turn on the rad fan, when the evap fan switch is turned on. I thought maybe power would back feed to the relay from the red and blue wire but, no dice. This relay does not appear to have a power source with how it's curtebtly wired.
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1984 Vanagon GL
1984 Vanagon Westy

[jlrftype7]

Okay- that gives me something to follow along and possibly match with our A/C system.
_________________
'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto

[Gauche1968]

So, there is this wiring diagram in the Bentley. It's not an exact match to my system, but it is close. I don't have any idle stabilizer valves, and some of the wire colors don't match what I have, but the basic lay out is the same.

The trouble seems to be with the "AC Compressor Cutout Relay." I don't see how power gets into this relay. Pin 30 is connected to a red wire with black strip that comes from the evaporator housing. The diagram says this is coming from the thermostat, but where does the thermostat get power? Also, the diagram says the red wire with blue stripe on pin 86 goes to the Radiator fan relay, but that doesn't seem to be the case on mine. It goes towards the radiator fan itself. There is a seperate red with blue wire from the rad fan relay also. Unless those two wires are joined somewhere? At any rate, I am not sure what it's purpose is.
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1984 Vanagon GL
1984 Vanagon Westy

[jlrftype7]

30 is from the Temp switch, after IT gets it from the Evaporator Switch. SO, EVAP fan switch on, sends power next door to the Thermostat adjustment assembly. IF, the sensor bulb allows the power to come out of the Thermostat by deeming the EVAPORATOR is getting warm enough to turn on the Compressor.
The Compressor Cut-out relay is used to TURN OFF the Compressor. Now I see the Pin arrangement. AT rest, the relay normally ALWAYS sends power out via the 'resting' contacts inside the relay.
Once the relay is powered up, that moves the contacts away from the rest position, turning off the Compressor power.

So, you should be able to drop the front Duct Section to access your two switches, and see why you HAVE Fan Control, but no power out to the Compressor from the T-stat, if you haven't done this yet.
In my NOTES ON EARLY SYSTEM thread, you can see the mess of wiring for those two controls, shown in one picture since I have the duct all apart. Since there are TWO legs OUT of the A/C thermostat, and you are showing 2 connectors before the wire gets to the A/C cut off relay, you might have an open circuit there, or a mouse damaged wire. I thought you said the Radiator Fan was coming on LOW correctly when selecting A/C on. That SHOULD mean your A/C thermostat works correctly for the leg going DOWN to the Cooling Fan Relay in the diagram. 86 coil power to that relay.

Last NOTE- you MAY, or MAY NOT, have issues with idle load and A/C compressor LOAD being on, AND NOT having the Vacuum 'IDLE UP' or Idle Speed Stabilizer vacuum valve mounted on the rear firewal of the engine, behind the Intake Boot area. If you DO have one of those vacuum valves, you will get an increase in idle speed of the engine, to assist in keep the engine from dying out at idle with the increased load of the A/C compressor engaged.
Picture of the wiring, notice the use of SCOTCH LOCK 3M wire connectors? These are notorious for open circuits or voltage drops as they age, or loosen up in tension on the wires they're crimped through. Your issue could be as simple as one of these failing.

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'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto

[Gauche1968]

Thanks jlrftype7,

Yes, I just got through dropping the control panel and the "wind tunnel section." There is power on the green wires at the connector that runs from the fan switch to the thermostat switch when the fans are on. There is no power "coming out" the other contact on the thermostat switch, to the solid red wire, which becomes a red with black stripe further in its run to the compressor cut out relay," with the thermostat turned on. Mechanically, the switch seems to function fine, but there is no "signal out" to the compressor relay. So, is this a bad switch?
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1984 Vanagon GL
1984 Vanagon Westy

[Gauche1968]

"30 is from the Temp switch, after IT gets it from the Evaporator Switch. SO, EVAP fan switch on, sends power next door to the Thermostat adjustment assembly. IF, the sensor bulb allows the power to come out of the Thermostat by deeming the EVAPORATOR is getting warm enough to turn on the Compressor.
The Compressor Cut-out relay is used to TURN OFF the Compressor. Now I see the Pin arrangement. AT rest, the relay normally ALWAYS sends power out via the 'resting' contacts inside the relay.
Once the relay is powered up, that moves the contacts away from the rest position, turning off the Compressor power. "

Yes, but what sends the signal to this relay to "turn on" and thus turn off the compressor? Is it the removal of power to terminal 30 when the thermostat switch turns power off? Also, I am not sure what the purpose of this relay's connection to the high speed rad fan relay is?

And yes, the low speed rad fan comes on with the evap fan. That relay gets power on the green wire that starts at the fan switch and then "makes a stop" on one leg of the thermostat switch, before traveling down to the radiator fan relay.
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1984 Vanagon GL
1984 Vanagon Westy

[jlrftype7]