Early model r134 conversion question

[shawmcbigdis]

So I've read this thread; https://www.r3vlimited.com/board/for...ion-thread-diy and figured this wouldn't be to hard to finally get the AC working (for the first time under my ownership) and have a modern refrigerant.

So I bought everything from the thread and got to work. Well I think my big problem is I have an early car (1986) and I think this write up cover a late model. So the first issue I have is the pressure switches (yes plural) on my drier. What the heck is up with this?




From what I can tell the top one is the standard switch that should turn the fan on low when the compressor pressurizes the lines. That second one on the bottom right seems to be wired to the temp sensors at the top of the radiator housing. So at first I thought maybe the early model pressure switch is a 3 wire, one for low and one for high, but no it is still a 2 wire, just a different connector. I plan on running a cheaper single speed aftermarket fan, so I jsut need to make sure the fan gets single to turn on from the pressure and the temp, not 100% on how to get those 2 feeds from in this scenario.

Second issue. Car had the Denso compressor on it, so I ordered the 4 season Bosch with black pressure switch form rock out, since the stock on had a small black box with a single wire coming from it. However, the new compressor has 3 wires coming off of it? I don't know where they go in either scenario as the compressor wasn't hooked up when I got the car. Can I still use this new compressor or do I need to get a different one?



Any AC guru's got any ideas/tips for me?

TIA

[cory58]

This might help a little - 134a conversion works fine with the 2-switch set up on the dryer. I have it on both of my E30s.

[ZeKahr]

So the first issue I have is the pressure switches (yes plural) on my drier. What the heck is up with this?

The green switch is the high-pressure cutoff switch and the black switch is the low-pressure cutoff switch. This is the factory setup on R12 E30s. R134a cars have a single pressure switch; I guess they finally figured out how to combine the high/low switches into one switch by the time R134a came out.

From what I can tell the top one is the standard switch that should turn the fan on low when the compressor pressurizes the lines. That second one on the bottom right seems to be wired to the temp sensors at the top of the radiator housing. So at first I thought maybe the early model pressure switch is a 3 wire, one for low and one for high, but no it is still a 2 wire, just a different connector.

The pressure switches on the receiver-drier don’t have anything to do with the AC fan or radiator temperature sensors; they’re there to shut off the compressor in case the high/low-side pressure readings are out of bounds and thus prevent the compressor from prematurely failing.

I plan on running a cheaper single speed aftermarket fan, so I jsut need to make sure the fan gets single to turn on from the pressure and the temp, not 100% on how to get those 2 feeds from in this scenario.

the aftermarket AC fan only needs a signal from the one of the temperature sensors. The easiest setup is to wire one terminal to the black wire going into the resistor for the factory AC fan and the other terminal to the brown ground wire the factory AC fan is grounded by. This will power the fan on using the “low-speed” white temperature sensor.

Second issue. Car had the Denso compressor on it, so I ordered the 4 season Bosch with black pressure switch form rock out, since the stock on had a small black box with a single wire coming from it. However, the new compressor has 3 wires coming off of it? I don't know where they go in either scenario as the compressor wasn't hooked up when I got the car. Can I still use this new compressor or do I need to get a different one?

Yeah that’s odd. My 86 Eta has a Bosch compressor with the diode (AKA black box) and single wire. Not sure what the other 2 wires are for. I’d reach out to the place you brought it from and ask them about the wiring on that compressor