A/C Operating but No Cold Air

[cthomasparr]

Hello,

I tried for the first time to get my 96 318IC's A/C to work. All I know is that it never did, since i have owned for the last 4 years

I put a manifold gauge on the high and low ports. the lines were charged from a car just worked on. I was surprised when I opened them up that there was some residual pressure.... I am pretty sure that both high and low were at 65PSI with car not running.

I started the car up and low dropped to under 15 and high was around 90.

I started charging the low side, trying to target around 30-35 PSI. Either I overshot or the car pressure was still rising but it went to 42 low 220 high. when shut off around 110 PSI on both.

There was nothing but warm air. It is possible I was not even setup correctly to have the AC working (on the climate control, turned AC on, AUTO off, set desired temp lowest setting, fan on max). The AC compressor was engaged and pressure readings seemed kind of reasonable.

Two issues I would like to resolve that hopefully can get me cold air.
1. The radiator/condenser fan did not come on. The water temp seemed to reach 1/2 way between cold and hot but didn't keep rising.
2. Warm air was coming out of the vents.. not just the lack of cold air. Was a pleasant low 70F degree day and vents were warm.

One other issue may be that the outdoor temp reading on the dash that warns about ice.. it thinks it is winter time. seems to be about 40-50 degrees colder than it really is.

Any suggestions how to move forward and what are normal pressure readings? Also i noticed that the pressure low and high seemed to rise slowly as the car was idling. I didn't notice an increase in engine speed so this had me kind of puzzled.

Thanks for the help!

[flyfishvt]

First. The outside air temp reading is not connected to the HVAC system. It has no effect on it. It doesn't matter if it reads -30 or 220.

The aux fan should turn on as soon as the a.c. compressor kicks in. It's hard to get cold air without that fan running. Drive the car around for 15 minutes or so and see if you get cooler air. There are lots of reasons for the fan not to come on.

When you filled the system did you pull a vacuum? Dud you put the correct amount of ounces In? Never fill an a.c. system to a certain pressure. Always fill it by weight.

[cthomasparr]

I added by pressure. I may resort to a complete vacuum to make it accurate.

The fan not spinning is a concern. I will try a drive and also grab the service manual and my multimeter and see what I can find.

Does the warm air make sense? I guess if the condenser is not being cooled... or possibly even warmed by the radiator, maybe I could have the reverse effect of warming the Freon??

I am mostly concerned about the climate control (and my use of it) Up until now I almost always turn it off, so I never really had faith that the settings were correct.

Thanks

[samy01]

I added by pressure. I may resort to a complete vacuum to make it accurate.

Just get the old gas out, vacuum and then put in the correct weight.

Edit: I was wrong, A/C gas can be filled by pressure.

[cthomasparr]

I went through some troubleshooting with the electric fan. The car is a convertible 318 with auto transmission.
I first tried to rule out the temp sensor switch on the radiator. I shorted both the high and low speed fan wires and the high speed fan worked, low did not.
Both high and low speed fan had 10-12V.
I removed the relays that were associated with the AC. I swapped the low speed fan and ac compressor relays and still no fan action shorting out the temp switch.The AC clutch was working yesterday, so I trust that relay.
I went through a bunch of fuses and from what I could tell they all looked good. The 5A with a plastic window were tough to see(at least for me)
When I checked the low speed relay, the manual said that both 86 and 30 should have voltage. There was voltage on 30, but not 86.

I guess this is pointing me towards some wiring issue? or maybe a bad fuse that I missed. should have done a continuity check.

Any thoughts where to go next? I can't seem to dig up a wiring diagram that shows the fan.

Thanks again for the assistance.

P.S. The wiring near the fan looks good from what I can see. A buddy has an e46 and he learned that there was a signal wire that controlled the fan speed. Mine looks like three wires, so I guess that is a simpler setup? The wires ran through what looks like a metallic rod. Is that some kind of temp sensor or resistor?

[cthomasparr]

Kind of curious what that metallic rod is if anyone knows.

[samy01]

86 is getting power from F16, which is only 12V+ when ignition is on.

[cthomasparr]

F16 appears to have voltage when the ign is on. Fuse is good

[samy01]

If you have no 12V+ at 86 of relais K21 (low speed relais) with ignition on, but have 12V+ at F16, then you need to do a resistance test from K21 86 to F16 to check if the line between F16 and 86 of K21 is intact.

[cthomasparr]

I will verify that i have the correct relay. I believe it was closest to the firewall and was pointed out in the Bentley manual. If this relay triggers the low speed fan, shouldn't the low amperage part of that relay only be powered when the fan should be energized? I can understand the high amp side always having power, but the low amp(86?) being energized by the ecu or dash controls only when the car is running, AC is on, etc. Is that not true?

Also, does the wiring from F16 to K21 goes to several other components?

I would not be surprised that a wire has been chewed through. this car had evidence of mice living in it at some point and I think a miracle that no problems have surfaced.

[samy01]

If this relay triggers the low speed fan, shouldn't the low amperage part of that relay only be powered when the fan should be energized? I can understand the high amp side always having power, but the low amp(86?) being energized by the ecu or dash controls only when the car is running, AC is on, etc.

It's negative/ground controlled at 85/85b, so it should and could have 12V+ at 86 when ignition is on. That wouldn't make the fan start because the coolant temp switch or the A/C would need to provide negative/ground to close the electrical circuit.

I'm not sure if there should be 12V+ with the ignition on or if it has to be ignition on and A/C on. I think it should be 12V+ with only the ignition on, otherwise it wouldn't make much sense, since the negative/ground is already controlled by the A/C module or the temp switch.

K21 can get negative/ground from the A/C computer, as it seems. i'm not sure if i'm reading this correct. The A/C computer/module (i think that's the module where you press the A/C and temp buttons inside the car) will send negative/ground to K21 via path "B".



Therefore i'd go about it this way:

1) check function of low/high speed of fan. Use 12V power source that has a fuse built into the wire/line, so nothing overheats in case of a stuck motor.
2) check the wire i mentioned in post 9.
3) check the wire i described in this post.
4) ckeck all fuses, wires, relays systematically.

[cthomasparr]

Thanks for the guidance and wiring diagram. Very helpful. Will check it out in a few hours

[cthomasparr]

Now on closer inspection I see an issue. It looks as though the 86 connector on both relays mounts (low speed fan and ac compressor) Is no longer visible. I did take my time removing these relays and gently pulled straight up.

actually each socket has 4 female connectors. I need to find a wiring diagram that matches what I see

[samy01]

i guess making sure your car matches the wiring diagram would be more solution oriented

[cthomasparr]

wiring diagrams seem to be more harm than good as I can't find one that matches what I see. To add to my confusion, I have a single primary electric fan. It looks like some models, maybe even 4cyl have an auxiliary electric fan as well.

If I work backwards and test the fan's low speed motor, how do I do that? The fan wire harness has three wires. A brown, I assume is ground, goes directly to the motor and then there is also a black and blue wire. The black and blue both go to a resistor mounted to the fan and another blue wire exits the resistor and goes to the fan motor.

[samy01]

What? The electric fan ist he auxiliary fan. There's only one.

If you can't read wiring diagrams, or how to get the correct wiring diagram if you think this one isn't good, and don't know how to test the fan, then i would strongly recommend stopping at this point because of safety reasons and bring it to a mechanic.

[cthomasparr]

Low and high speed fan work All relays appear to be working also. Wiring diagram shows low speed fan grounded through ecm as well as climate control/ac pressure switch. Probably ac pressure ok because compressor kicks in
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