Bypassing AC low pressure switch

[baltik]

My AC was last charged about 5 years ago (r134a). Lately it's been getting less and less cold and today when I went to turn it on I can hear the relay click on, the radiator fan turns on but the headbanger cabinet fan does not turn on. My assumption is that too much refrigerant leaked out. I am not looking for a long term solution since I'll be pulling my engine soon and opening the system anyway. What's the best way to bypass the low pressure switch and force the compressor on so I can feed it a can of 134a from FLAPS just to get a few more trips under my belt.

[piruvan]

Check the fuses behind the left rear pillar. Two 20amp fuses work the condenser. One on mine was blown. Don't bypass the low-pressure switch (???) just charge it with another can. R134a leaks out of the Vanagon R12 system. Switch to RedTek or Envirosafe.
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'89 Vanagon GL "Whitestar" Wolfsburg edition. 4-speed, 2.1L
'06 Accord EX-L 5-speed

[MarkWard]

Are you asking where the switch is located or how to jump it? Easiest would be to temporarily ad power at the compressor electrical compressor. Usually just connecting a can is enough to close the switch. The compressor may cycle but each time it can draw in a little more freon.
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[baltik]

Got it - I believe the location is near the fuses inside the westy cabinet. Just to re-confirm, if the low pressure switch is the culprit, the AC fan should not go on right? or just the compressor?

[MarkWard]

You don't say what year or if it has factory AC or Dealer Installed AC. Its very rare to need to bypass the low pressure switch for a charge.

We'd need to know more details about the AC to answer your rad fan low speed question. Not all are wired the same.
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[baltik]

This is a 1990 Westy with factory AC, converted to 144a

thanks!

[MarkWard]

Looking at the wiring diagram 97.144 and 145 It appears that the low speed radiator fan works independent of the AC pressure switch. The wiring diagrams are not always 100% accurate though.
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[kamzcab86]

[baltik]

Got it - thank you. So it seems like i have multiple issues then
issue 1 - AC fan not turning on, will check duses, relays and grounds
issue 2 - lack of 134a - jump the blue wires on the low pressure switch and feed a can until up to temp

[MarkWard]

Sorry, I misunderstood. I thought you were asking about the radiator fan, not the blowers on the evaporator core. The AC wiring is sort of complex and without using the wiring diagram in the manual, could be difficult to troubleshoot where the problem is. I can make out the 50 amp fuse in Kam's picture and if I had to guess, I can make out the two blower fuses in the rear corner of her picture.
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[dgbeatty]

You add enough refrigerant to close the low pressure through the HIGH side with the engine off.
You will positively need to find the leak, repair the leak(s) and then evacuate the system to remove any air or moisture that has creep into the system.
There are no shortcuts if you want it to work properly.

[kamzcab86]

[baltik]

All the fuses look clear... is there another good spot to check?

[MarkWard]

You need to test them for power. Looking is not enough. A 12 volt testlight is handy to have in your arsenal.
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[baltik]

Just to wrap this up - I ended up connecting a can of 134a, compressor spun up, I was able to get to the desired pressure, AC worked well enough for our trip and still blows cold. Thanks for all the help

[Abscate]

Monitor it over the summer. It usually doesn't leak out slowly over five years, you develop a leak, which you have to fix.

The best way is to have your Freon 'recovered' free where I am, then put the system under vacuum for a few hours, then see if it holds vacuum

If it does, then recharge by weight - much easier than trying to do the calc for low/high/temp

Every Oring that is disturbed gets replaced.

If it holds vacuum for 4 hours, no need to replace drier.

Manifold, gauges, and pump cost about $150 from HF. I just did my tenth AC job with them, so Im down to 'shop supplies' on a per use basis.
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.ssS!