SF East Bay AC specialist?

[Californio]

Hi folks,

I need an East Bay mech who's familiar with these AC systems to drop the ceiling cabinet and repair/replace the AC thermostat.

Anyone have good ideas? Obviously there's Buslab but they're a bit rich for my blood on the price side, and there's a place called Berkeley Radiator, but I don't know if they'll drop the cabinet.

Anybody have this sort of stuff done here?


Thanks!

[stevey88]

There is no A/C thermostat in the overhead cabinet. However, the A/C thermostat capillary tube is there. Is that what you need to replace ?
Where are you located ?
_________________
Steve

87 Westfalia full camper 4 speed

[Californio]

Yes, that's what I meant. To be more specific, it's the device labeled 1-A/C Thermostat on Bentley 87.3. If I bypass this, the AC works fine; if not, the compressor clutch will not kick on. I don't see any way to replace it or fix it without dropping the cabinet.

I'm in Oakland. Thanks for your reply.

[stevey88]

The A/C thermostat is a black box mounted on the D pillar. Two black wires come out of it and go to the evaporator to measure the temperature there. How did you by-pass the thermostat ? As far as I know, the thermostat is electronic and it compare the setting of your A/C temp knob with the value of the probe that is inserted in the evaporator. Before you spend big effort to drop the cabinet, check if the wiring from the temp setting knob to the thermostat is good. Measure the resistance between pin 2 and 3 of the plug that goes into the thermostat ( see Bentley page 97.140 ). Turn the temp knob to see if the value changes.
_________________
Steve

87 Westfalia full camper 4 speed

[Californio]

I bypassed the thermostat by supplying current directly to the AC relay.

Without doing that, the current coming from the thermostat/into the relay is +-12VDC, but it doesn't have the amperage to work the relay. Makes no difference where the dash knob is at.

Any idea what the resistance should be on the pins of the thermostat plug?

[stevey88]

If all you did was to supply 12V to the A/C relay, you are jumping the gun trying to drop the rear cabinet. There are many things that can be wrong to prevent the thermostat of supplying power to that relay. The part that is inserted into the evaporator is a thermistor, the resistance of the thermistor changes in value according to temperature. The resistance of the temperature control knob also changes according to your setting. The thermostat compare the two value to decide if the clutch should engage or not. So you need to check the following:
1: Does 12V get to the thermostat when you turn the A/C on ?
2: Do you see the resistance changes AT THE thermostat when you turn the temperature control knob ( it varies from 0 ohm to 10Kohm )?
3: Is the thermostat properly grounded ?
4: Is the thermistor working ? The wires for this came out of the thermostat and is not detachable, you need to insert two pins through the insulation to measure the resistance. I do not have the value @ room temperature on hand.
5: if all are good, measure the output of the thermostat ( blue wire ) to see 12V is getting out. If no output, then it may be bad. Get a new/used one to replace the old one. Leave the thermistor out to see if the clutch engage now. If it does, keep the old thermistor by cutting the wire and connect to the replacement thermostat. The last thing you want to do is to drop the cabinet.

One stupid question, is your S12 fuse there ?
_________________
Steve

87 Westfalia full camper 4 speed

[Californio]

The odd thing with this, to me at least, is that 12v is coming out of the blue wire from the thermostat into the AC relay. But it's only nominally 12v; it does not seem to have enough current to trigger the relay. When I remove the blue wire from the relay and supply a real 12 volts, it all works.

There is a good 12 volt connection at the dash switch, and the thermostat is grounded (no corrosion at the screw.)

If there is only the thermostat between the dash switch and the AC relay, what else could it be? That was my line of thinking.

Thanks again for taking the time to think this through. I'd much rather not have to drop the cabinet if possible.

The thermostats are hard to come by and sell for something like $275, too!

[stevey88]

[reido]

Back to the original question:
The folks at Buslab referred me to http://www.berkeleyradiator.com/
Haven't used them yet, so I can't recommend either way...
_________________
1990 Camper, 2.1 stock AT...sold july2018

[Californio]

Yes, Berkeley Radiator is good, but my impression is that they like to work mostly on the mechanical side of the AC systems, not the electrical. They brazed up a fitting for me a year or so ago and, last time I checked, no leaks. I just want to find the right person to drop the cabinet, and not sure they're the ones. If, that is, I can't diagnose/fix it myself...

[Californio]

Stevey, with the thermostat connected, I measured 12 volts at the connection between the blue thermostat wire and the AC relay (on the relay.) But this 12 volts, which I was calling "nominal," would not trigger the relay. When I supplied an external 12 volt source to the blue wire (jumpered from the fusible link), the relay works fine, and the compressor kicks on.

Then I went back from there to the thermostat itself, to see if there was a connection problem. This seemed very unlikely as the AC shut off suddenly, and there was no apparent damage to the connectors. The pin from the thermostat connector reads 12v. Supplying a "real" 12v to the connector from the thermostat also kicks the relay on.

This is why I thought the problem must be upstream from the thermostat connector, but downstream from the dash switch. That pretty much leaves the thermostat, unless there is some other funky connection in there that would supply the "nominal" 12v but not allow enough current to pass for the relay to actuate.

This was all a while ago, so it sounds like I ought to go do some checking again. The thermostat probe will be next.

[MultiVanAgain]

I recently took my rig to Berkeley Radiator Works. The owner of the place seemed a little rigid at first but turned out to be a great guy. He figured out what was wrong with my system and made the necessary repair. My problem was mechanical so I can't comment on whether he deals with the electrical side of things. I can say that he knows the Vanagon A/C system very well and seems to be an honest guy.

I just got back from a 3-night camping trip in the Sierras and we had the A/C on while driving on I-80. The wife and kids were happy as the system worked like a champ blowing cold air. If you can't fix the problem yourself, I'd give that shop a call.

[Californio]

Yes, thumbs up for the owner of Berkeley Radiator, he's honest, doesn't overcharge, knows his stuff. Small shop with no employees if I recall.

Almost across the street is Berkeley Auto Service, also good for Vanagons. Roger knows them and charges way less than some others in the area (he installed my conversion engine 11 years ago.) I used to leave beers in the fridge to get him started in the morning...maybe helped with the bills...

But now I'm getting the idea I can fix this AC myself...

[Californio]

Ok, I confirmed my findings from before:

1. The system starts and works perfectly if I jumper to the blue wire from the thermostat (stripped wire above the connector to make sure it wasn't that.)
2. When NOT jumpered and with the connector NOT attached, voltage is around 13 with the engine running.
3.HOWEVER, and this is the difficult part, when I reconnect the blue/brown wires to the AC relay, the relay does not kick on and VOLTAGE DROPS TO ZERO.

In other words, even though there is nominal voltage, placing a load on it shows there is not enough current coming through to trigger the relay.

Is it worth doing the same test BEFORE the thermostat (green wire from dash switch)?

[stevey88]

Ok, let me confirm this is what you see:

1. When every thing is connected, there are no voltage from the thermostat blue wire output.
2. When everything is still connected, if you put 12V at the thermostat blue wire ( stripped insulation above the connector ) the clutch will engage.

Then assuming you have measured the resistance of the temperature setting input to the thermostat at the thermostat connector, the resistance will varies from 10K ohms ( warmest setting ) to 0ohm ( coldest setting ), short out the thermistor wire to see if clutch now engage. This is to fool the thermostat to think the temperature of the evaporator is high.
I have just measured the thermistor resistance, it is around 9K ohm at room temperature. It has a negative temperature coefficient that means the resistance goes up when temperature goes down.
_________________
Steve

87 Westfalia full camper 4 speed

[Californio]

Yes, that's it.

The only odd thing (to me) is that with the double pin connector disconnected, the blue wire shows +-12V with the dash switch on. Then, connecting it to the AC relay so there is load on it, the voltage disappears.

Just to get it back up and working, I bypassed the thermostat altogether by cutting the green-in and soldering it to the blue-out. Works perfectly but, as expected, there's no temp control from the dash switch--it just turns it off and on. Which is how I use it anyway--never had it get too chilly in there.

Is there anything wrong with leaving it like this? Eventually I'd like to get it back to stock, but for now, good enough for me. Unless it will damage something.

[stevey88]

If you mean connecting the 12V input of the thermostat to the output blue wire, yes it will work.
_________________
Steve

87 Westfalia full camper 4 speed

[Californio]

OK, will leave like that for now. The thermostat can wait until I or someone else does the resistor pack for the fan motor, also up there in the cabinet IIRC.

Thanks so much for your help--I'll come back to this post when testing time comes!

[madspaniard]