Help me diagnose my AC trouble

[15Michaeljoseph]

Alrighty. This forum has a lot of smart people on it...I ain't one of them. Please give me your opinion based on my info. I'm trying to make this easy to understand.

Car: 1/1987 BMW 325is, has had an r134-a conversion.

The lowdown/ my steps: Make sure foot well vent slider is all the way to the right. Turn on blower. Press snowflake button, and it lights up a pretty blue. cool. but not cool enough. Pop the hood, and look at the compressor. clutch isn't engaged, and won't engage even if r134 is added to system. Look through the kidney grills, and the Aux. Fan isn't going either. hmmm okay.

What I've concluded from tests:

• The compressor isn't getting any voltage at it's plug (so it isnt kicking on)
• The Aux fan will work on HIGH only...and only if I use a wire to jump the pins on the sensor (the one on the radiator)

• Pulled K1 relay, and no voltage at pin 86, however pin 30 does have.

Through my internet research and personal 'gut feeling', I think this:

• I might be in need of a new 'Evaporator Temperature Regulator'... AKA this bad boy: http://www.redlinemotive.com/store/r...tion=000059647
• and/or I will need a new low speed fan resistor.

What I'd like to know from you gize:

• If the ETR is bad, will both the fan and the compressor not work when the snowflake button is pressed? I'm looking at this wiring diagram my mom gave me and it appears that way, but I'm not that well versed in this kind of stuff.

I thank you in advance and I really hope you can help me ;D

[cunninglinguist]

I'd check for a bad "compressor enable" microswitch before spending any money. This switch lives behind the ventilation sliders and can be bypassed (deleted) to restore power to the compressor.

[15Michaeljoseph]

So do you think that the fact that the compressor and the fan don't come on are actually unrelated? I will take the hvac panel off and look at that switch.

[cabriodster87]

http://wedophones.com/Manuals/BMW/1987%20BMW%203%20Series%20Electrical%20Troubleshooting%20Manual.pdf

Start on page 119, hope this helps.

[15Michaeljoseph]

http://wedophones.com/Manuals/BMW/1987%20BMW%203%20Series%20Electrical%20Troubleshoo ting%20Manual.pdf

Start on page 119, hope this helps.

well it actually was a great resource. I got home from school early today because of finals, and I have been fooling around with the AC since then. so new things I've concluded:

If I jump the compressor, the clutch engages
there is no voltage at the low pressure cut off switch on the reciever-drier (behind the passenger headlight
pulled K1 relay again and used my jumper wire to jump all four plugs in various configurations... fan didn't come on.
I took the hvac panel off, and got really scared looking at all the wires. since i had to pull the headunit I found a ground cable undone, so I plugged that shitz back in sounds better now.

Took the AC snowflake/recirc. switch off, and found nothing wrong with that...i think.


someone test this out for me: put the key in and turn it to get the radio and ac, but don't start the engine. does the blower start blowing on it's own? what else happens? on my car all it does is start blowing at like speed 1 or something. I unplugged the switch, and jumped the plugs in various configurations, and the only reaction i got was when I jumped the top two plugs, and there was a noise like a relay clicking. but nothing else. the blower didn't turn on. huh.

As far as i can tell:

The fact that the fan doesn't come on with may be unrelated, and may just be the relay, but I really don't think so.
power is getting to the A/C/recirc. switch, but something's not sending juice to the compressor.
there's no voltage going to the low pressure sensor...so


So what stands in the way of the compressor and low pressure sensor getting voltage? Does the Evap. temp. switch cut power not only to the fan and compressor but also to the low pressure switch?


Thanks for all the help so far guys, I'm sorry to be a pain in the A.

[cabriodster87]

Do research on the ac circuit "diode", its inside the fuse box. it may be bad.

[cabriodster87]

Im assuming your system is charged (low pressure switch closed)

[15Michaeljoseph]

Im assuming your system is charged (low pressure switch closed)

Going to look up the diode right now. The system is charged, but like I said the connector to the low pressure cut off is not getting any voltage at all, I unplugged it and tested it with a multimeter.


--Mike

[15Michaeljoseph]

just an update, I've been busy with final exams. I took the AC snowflake switch out and pulled it apart and cleaned it. that's about all I did since my last post but i thought it would be worth mentioning. #bump


--Mike

[15Michaeljoseph]

just an update, I've been busy with final exams. I took the AC snowflake switch out and pulled it apart and cleaned it. I also pulled K1 and tried to get the fan to come on. the good news is I know my compressor is good because i jumped that using the 12v from the washer pump.
that's about all I did since my last post but i thought it would be worth mentioning. #bump


--Mike

--Mike

[15Michaeljoseph]

Update: Got around to more tests (so busy with other things) and found that the low and high pressure switch doesnt get any voltage. tracing it backwards. pulled the knee bolster to get a look at the evaporator temp sensor, and found it unplugged!! plugged it back in, but haven't had the car on yet to check.


--Mike

[15Michaeljoseph]

well, got my other repairs done and fired her up to try the AC just for the hell of it. Made sure it was charged... Nothing. I'm going to replace the Evap Temp Sensor because they aren't crazy expensive and it would completely rule it out. at this point I'm looking at two parts that are messing up AC operation, the Evap Temp Sensor, and Evap Temp Regulator. #Bump


--Mike

[e30rapidic]

how do you know its charged? are you testing AC readings while the car is running?

[ahlem]

If you jumper the coolant temp sensor you should hear the low speed and high speed relays click. If both click and only the high speed fan turns on, you need a new low speed fan relay. Auxiliary cooling fan that is.
If you can only get your heater fan to run on high, you need a heater fan motor resistor pack. See write UPS in the DIY section or in your Bentley Manual. Once you Eliminated these two, you can move on to your AC. Too many things wrong at the same time is not good

[15Michaeljoseph]

how do you know its charged? are you testing AC readings while the car is running?

Yes, car running, snowflake button on, fan blowing on 4


--Mike