Radiator Fan wont shut off after AC compressor kicks on

[Sharp64]

I have gone through multiple threads and not finding this exact scenario. I'll likely throw out way too much info, but here goes.

I have an 85 Westy, but based on some wiring cues, it seems I have wiring that is more in line with the 83/84 diagrams. It does not have the resistor in the circuit called out for in the manual. I have a Small Car in dash AC unit that when first installed, seemed to work flawlessly. Last year, the radiator fan began sticking in the on position whenever the AC was turned on. We incorrectly thought it might be due to the use of a later fan motor and have since switched over to a Small Car radiator shroud and fan with a lower draw.

If the ac switch is turned on and the heat is on, or at least at a level where the AC compressor doesnt kick on, the radiator fan does not come on. As soon as the AC compressor kicks on, the radiator fan jumps to the high position and doesn't shut off regardless if the AC system switch is shut off as well as the ignition turned off. The only thing that shuts it off is either pulling the #7 fuse or the relay on the left under the dash near the ground trees. Once plugged back in or the fuse is replaced, the fan goes back to normal and stays off. I haven't been able to get the van warm enough to get the fan to turn on without the AC running, so I don't know if it would stick on if it kicks on without the AC.

I have tried unplugging the thermo switch on the radiator with no effect. I previously changed the relay with no change. I did order a couple of replacements to have just in case. Was going to get a new thermo switch as well to have as a backup.

I thought perhaps there was a ground issue but have cleaned the three main grounds as well as trying to bypass the ground tree and grounded directly with no change.

Short of wiring in an "interrupt" switch between the fuse and power source to reset things I am out of ideas. Any help or ideas would be appreciated.

One other note, when the AC system is turned off and the fan allowed to run, the #7 fuse gets HOT. Really hot. It literally melted a fuse last year.

Another note, when I got the van back from having the radiator fan and shroud replaced, I drove it around for an hour or so with the air on and had no issues. Then it started acting up again for no apparent reason. Same thing this morning. I "programmed" the ECU again as I had accidentally grounded it and changed the settings. It worked fine in the driveway. On and off multiple times but when I drove for a bit, the fan went back to not shutting off. I tried going through the programming process a couple of times with no change. I did leave it run to see if it would shut off on its own and after 2-3 minutes it was still running.

Thoughts?
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1960 Indigo Blue Ragtop (Blue Barry)
1967 Ghia
1985 Westy Money Pit
“...some men aren't looking for anything logical, like money. They can't be bought, bullied, reasoned, or negotiated with. Some men just want to watch the world burn.” - Michael Caine

[AndyBees]

Where does the current come from that powers the Relay?

My 89 with the 2.1 engine will warm-up enough idling to kick-on the radiator fan. Once it kicks-on the first time, it will continue to kick-on and off (cycle) as long as the engine is idling. Give yours a try. Maybe drive it around the block a couple of times then let it idle in the drive-way... preferably with the front of the Van facing away from the prevailing wind.
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'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.

[Sharp64]

[ALIKA T3]

Your van has a dealer added AC, so the wiring is taped into the 2 speed fan somewhere. I think there are diagrams out there but you'll have to trace the wires unless somebody familiar with this set up chimes in.
If the thermoswitch is unplugged and it still runs, it's definitely on the AC side of wiring.
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Silicone Steering Boots and 930 Cv boots for sale in the classifieds.
Syncro transmission upgrade parts in the Classifieds.
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http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
Syncro http://www.thesamba.com/vw/forum/viewtopic.php?t=4...num+gadget

[Sharp64]

[crazyvwvanman]

Yes, while the fan is misbehaving and running on, remove the lower grill and unplug the radiator temp switch connector.
Does that turn off the fan?

The answer will help us know where to look.

Mark

[Sharp64]

[crazyvwvanman]

While the fan is running on, measure the voltage at each pin of the rad temp switch connector while it is unplugged from the switch.
One probe on chassis ground, then the other probe on each pin of the connector in turn.
Write down the exact reading for each of the 3 wires and share them here.

Mark

[AndyBees]

[MarkWard]

The aftermarket radiator fan might be acting like a generator. Maybe a diode in line to the power lead.

I’m not familiar with the small car AC, but have a Vintage Air dash AC. I fabricated my own radiator wiring circuit. The challenge was to combine the radiator temp switch function to the ac pressure trinary switch function.

To accomplish this, I wired the radiator fan switch to provide grounds for the radiator fan relay I added. I then used the trinary pressure switch to also provide grounds to the radiator fan relay. Basically 2 circuits independently controlling the radiator fan. I believe I posted this before.

I have no idea how your aftermarket AC is connected to the Vanagon wiring. Perhaps a wiring diagram would help. Sounds like the points in a relay are sticking together probably from heavy load and not being sized correctly.
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[crazyvwvanman]

Yes, an accurate diagram of the A/C wiring may be essential.

While they are labeled as 12v relays most small automotive relays will actually turn on with a much smaller trigger voltage than that, maybe even 4 or 5 volts.
Once the relay is triggered on it will stay triggered with even less volts, maybe even only 2 or 3 volts.

So, what this means is any backfeeding to the relay coil can be a very weak source and still keep the relay active when you think it shouldn't be.

If the output of the relay can somehow backfeed even through other devices to the relays own coil wire, the relay can become LATCHED in the on position because it is now feeding itself to stay on.


Mark

[Sharp64]

I am trying to make heads or tails of the AC wiring diagram. I may have come across something that could potentially be the culprit. Doesn't explain to me why it would be intermittent but looking at the wiring diagrams, one shows a binary switch and another a trinary switch. Looking at the drier, it obviously has a binary switch but finding 3 wires. One is to the condensor. The other connection on the switch has two wires coming off it. One seems to go up front and into the dash. The other looks like its going to the evaporator which doesnt make sense.

I will scan the wiring diagrams that I have and see if they make sense. I think something may be wired incorrectly.
_________________
1960 Indigo Blue Ragtop (Blue Barry)
1967 Ghia
1985 Westy Money Pit
“...some men aren't looking for anything logical, like money. They can't be bought, bullied, reasoned, or negotiated with. Some men just want to watch the world burn.” - Michael Caine

[Sharp64]

[Sharp64]