Help me with this A/C thing

[Das Delfin]

hey so I'm setting up my system to run on the original r12. I was all set to convert to r134a but my friend and I pulled a vacuum just for kicks and found out the original system still holds a vacuum. He has a 609 so we were able to get some r12 on ebay. Fast forward to today. I'm using the original two-pressure switch set up with a (new) old-style dryer

We charge up the car, it takes about half the first can, we go to start up the car to kick on the compressor, and the compressor doesn't turn on. The low side gauge is reading 60 psi at this point, well over the ~24 needed to close the low switch. So I jump both switches, ensuring continuity to the compressor, and still nothing. Then I take a voltage reading at each switch. The power at each switch is zero volts. So now I'm like - wtf

When I press my dashboard snowflake it lights up blue and the condensor fan kicks on. So I know those are both getting power. The idle surges a bit, so the ECU is getting the signal. Somewhere in between this and the pressure switches the connection is lost.

I've read about an "evaporative temperature regulator" located somewhere in the dash. I am prepared to dig in and replace this but I need to know is there anything else that could fuck me up? I'm SO close to having this finished. It was like a punch to the face today when my compressor wouldn't come on

[Das Delfin]

So I bought one of those from a local store online and will hopefully pick it up tomorrow and install it. I've searched the wiring diagram online and there is nothing else in the way

This could be why someone gave up on the A/C years ago.. something hard to trace etc. If nothing else it was only $40 for peace of mind

[Das Delfin]

ok well I'm going to try to update this thread along my journey

So I found a wiring diagram and basically the trace is slider switches > snowflake switch > evaporator temp regulator > low pressure switch > high pressure switch > compressor

The problem was I wasn't getting voltage to the low pressure switch. My snowflake and fan would come on but I wouldn't see voltage before the low switch. So I used the link above and realoem to find the part number ( 64508390158 ) and found one at eeuroparts.com for like $40 (they're local so I was able to pick it up next day).

I put it in today. It wasn't hard but it's in an awkward spot. Take off the lower steering column cover and look up on the right. It's part of the heater/AC assembly mounted up and behind the footwell vent. It's held in with a clip on top. Twist it out from the clip and unplug the wiring harness to get it out.

So I started the car, hit the switch, and! Still my compressor doesn't turn. So I jumped both pressure switches. Still nothing. I used a multimeter to verify that I now had voltage before the low pressure switch. Then I checked for continuity from the low switch output wire to the lead which goes directly to the compressor, which verified that the high switch was functioning and that the wiring was good. Then I checked for continuity from the compressor's ground to the battery negative. Also good. I don't think my low pressure switch is functioning correctly, but that's not a huge issue. With the motor running, there is a slight power surge when the low switch's leads are shorted, but I'm still not seeing the front of the compressor rotating.

And then I got to thinking: what if my compressor is bad? It holds a vacuum in the system so the seals are still good. How often does the coil go bad? It's only an electromagnet; there's not much to go wrong. So here's a picture



The screw in the middle is the ground. The screw also has a bracket which holds the pos wire in place. The pos wire comes directly from the high pressure switch and once it reaches that bracket, splits into two signals. One goes to the coil, which has a return wire finishing at the ground screw. But the other pos wire goes to the little white box directly to the left of the ground screw.

What is that box? A fuse? Oil level sensor? Heat sensor? I have an early model Denso compressor

Since EVERYTHING ELSE works (except most likely the low pressure switch, but I have to verify that with my gauges), I'm leaning toward a compressor replacement. But I'm trying to be sure because it's a lot of money

[jeffnhiscars]

I'm not quite following what $40 part you bought but I have 2 thoughts. One is that the probe in the dash you refer to goes in the evaporator to insure the system doesn't ice up. It's set to cut off the compressor at 37 degrees. I suppose in theory it could have failed in the open position and is preventing your compressor from engaging, but I'm doubtful ? If you do replace it be careful as it's actually quite soft and can deflect and block your blend door (AMHIK).

Second thought is that if your compressor is not engaging after jumping everything to power it, its more likely the magnetic clutch that has failed. I'm not sure they are serviceable, but any working stock compressor will handle r12. I have one laying around here as well as an r12 expansion valve (which is nla)

One thing for sure is that it's not being caused by your new seat shocks :)

Ok actually 3 thoughts....is your middle slider at least 3/4 to the right as that will prevent the compressor from engaging even if the snowflake is lit

[Das Delfin]

In some cars (87+ I think) there is a relay which talks to the evap temp sensor and the high pressure switch. This controls compressor operation. This is the part I was talking about. Since replacing it, I'm getting voltage down at the pressure switches. This means the temp sensor is functioning properly and the sliders also work (although they only work when all the way to the right, and I'm pretty sure they're supposed to turn on 1/3 of the way from the left). But again I'm getting 12v all the way to the compressor with the snowflake on.

Literally everything works except the fan clutch. I'm like..how probable is it that a coil goes out? After reading up on it, inside the compressor there are three electrical components: the coil, a diode for the coil (because when you switch off the compressor it can create a current flow back up the system) and a switch which reads oil temp. Any one of these could be at fault

The plan is to grab a new coil and go from there! I'll have to pick up an impact gun to take off the pulley nut. What a terrible predicament ;)

[jeffnhiscars]

The slider needs to be 2/3 to the right more or less and I'm not aware of a relay so am no help on that

[Das Delfin]

It's cool. Some cars just had the switch. Now I'm on the hunt for a clutch/coil/bearing assembly for a Denso 10P15E. Ebay has it brand new for like 175 but for another 100 I can get a whole new compressor. I'll have to check if it's R12 or R134a compatible but for the moment I'm looking for a used compressor to swap parts over

[e30rapidic]

run a 12V power supply directly to the compressor. You should hear a loud click, engaging the clutch. That will take out the guesswork of a compressor replacement at least.

[jeffnhiscars]

It's cool. Some cars just had the switch. Now I'm on the hunt for a clutch/coil/bearing assembly for a Denso 10P15E. Ebay has it brand new for like 175 but for another 100 I can get a whole new compressor. I'll have to check if it's R12 or R134a compatible but for the moment I'm looking for a used compressor to swap parts over

I'll check my spare and let you know.

[uturn]

No impact gun needed, just snap ring pliers and special pulley removal tool. Just be sure you don't get a worn clutch that slips.

[jeffnhiscars]

The compressor I pulled from my Cabrio is a Bosch. Sorry

[Economy Sport]

run a 12V power supply directly to the compressor. You should hear a loud click, engaging the clutch. That will take out the guesswork of a compressor replacement at least.

I just did this and it was surprisingly easy; the positive wire going to the compressor has a connector right next to the low-pressure switch connector (not sure if it's the same on newer models):



I ran a 3' jumper wire between it and the positive terminal on the left side of the firewall and heard a reassuring click as the clutch engaged.

As long as I'm here...On my car, the AC has not been working for at least 16 years, probably longer (P/O bought it in 2002 and it didn't work then). I recently started looking into it and was quite surprised that there is still pressure in the system (both high and low side) and no obvious sign of leaks anywhere. Unlike the OP, when I push the snowflake, the aux fan doesn't come on. I have read about a 3 prong switch on the radiator, but mine has 2 separate 2 prong switches, one for high speed and one for low. I shorted each of them out, and the relays clicked and the fan ran both speeds.

A few questions:
Since the system is under positive pressure and has never been opened, is there really any reason to replace the receiver/dryer? Along the same lines, wouldn't all of the mineral oil in the system still be there? Would there be any reason to replace it? When I jumped the compressor with the engine running and when the clutch engaged, it ran smoothly with no noises, which I took as a very good sign. However the aux fan didn't come on. I'm guessing the resistor or the ambient temp sensor is bad? The OBC doesn't work at all so have never seen a temp reading.

Once I get the aux fan sorted out I'll likely take it somewhere to get the system emptied in an environmentally responsible manner so that a precise amount of R12 can be added (mine takes 1100 grams or 2.43 lbs). I figure I could save a good bit of money by filling it myself using a scale to get the required amount into the system without overfilling (after I get the online EPA 609 cert of course). Cans of R12 are readily available on Craigslist for $20 to $30. Does anyone know what shops are charging these days for R12? I've read the prices have dropped considerably in recent years; might be worthwhile to just let a shop do everything.

Any info much appreciated!

[Das Delfin]

the wedophones website has the electrical troubleshoot manual for our cars. You can download it and trace the entire system.

If your system still has pressure and blows cold when you jump the compressor, don't open it up to add oil or change the dryer.

There's a chart which shows ideal pressures at certain temps in the R134a conversion thread. It shows both R12 and R134a specs. You might be able to use that to figure out how much more freon you need.

[Das Delfin]

I am leaning toward whole compressor replacement. I went over to a friend's house last night to pick up his old compressor but we couldn't figure out how to get his clutch off. I was expecting a circlip but it turns out the clutch top plate sits on with one bolt. Since it didn't readily pop off, I didn't want to force it and potentially ruin something.

Finding a clutch/coil/bearing kit for this compressor is hard. 10P15E is the designation for our cars. The E refers to the type of manifold (both low and high ports coming straight up). There is also a C (on Porsches) where one goes up and the other points toward the back. So the main unit itself is just a 10P15. Then there are v-belt clutches and serpentine belt clutches. The clutch kits I was able to find were either really expensive (more than half the cost of a remanufactured compressor) or for a serpentine belt application.

At this point I'm looking at a rock auto reman unit for $285 shipped. It's a Four Seasons 57352, which means it's for BMW, using the V belt, and was originally a 10P15E (but doesn't include the E-designated manifolds). I t has updated seals for R134a but they are backwards compatible for R12. There may be a cross-reference for another Four Seasons reman unit which is really the same as my 10P15E (but cheaper) but at this point I don't want to mess around too much. I'll have to figure out which oil to put in. I'm assuming it won't come filled with oil but that's something I'll have to double check.

[jeffnhiscars]

You may want to confirm if a replacement compressor comes with oil since it's more than likely PAG which is completely incompatible with r12'and the mineral oil that is used with it.