What is this wire for?

[Casey]

I noticed this loose when cleaning my engine bay today, and don't have a clue what it is.  It's behind the front driver-side headlight, and was wrapped around the larger blue hose:

[jbrasile]

Casey, check to see if it's not the plug for the aux fan

Tks,

Joe

[Casey]

Casey, check to see if it's not the plug for the aux fan

How would I check.  And what is the aux fan?

[jbrasile]

The auxiliary fan is right in front of your a/c condenser, which is in front of the radiator. It's job is to kick in when engine temp goes above 105 C or the refrigerant temperature/pressure reaches a certain level.

Follow the cable from the aux fan down to the bottom of the driver's side headlight, into the engine compartment and see if it's disconnected. If so re-connect to the plug in question. If the fan comes on then the temp sensor is shorted and needs to be replaced, for some reason this sometimes happens to these cars and someone in the past may have simply disconnected the plug to stop the fan.

If the fan doesn't come on (remember if engine temp is below 105 C and a/c is off it should not turn on), you can test it by applying 12V to the wire that's connected to the sensor, thermostat housing, right behind the engine fan, passenger side above water pump, test it with the engine off to avoid loosing fingers, hands, etc....

I am doing this from memory since I had a 79 300SD many years ago so if I am not completely accurate, someone pls correct me.

Let me know what you find.

Tks,

Joe

[1980sdga]

That looks like the location of the AC compressor clutch wire.  You should have a wire coming from that area of the wire bundle to a plug on the bottom of your compressor.

[jbrasile]

1980sdga, I think you are absolutely right!!! I should look at my 450 again, got confused because I replaced the aux fan last year and can't visualize where its cabel went into...

At any rate, Casey, it is either the compressor or aux fan.

Tks,

Joe

[koan]

Looks like A/C  connector with square holes for tags on GM A6 compressor. Most other connectors have round holes.

koan

[1980sdga]

1980sdga, I think you are absolutely right!!!
Tks,

Joe

Oh no, bad news...  It only happens three times a year and it's only May 

[jbrasile]

1980sdga, so you have two left....

Looking at the picture again I confirm, YES it is the compressor clutch wire!

Tks,

Joe

[Casey]

Okay, I can't find the other end.  I'm assuming the compressor is the thing on the bottom side of the engine with a belt attached to it on the same side of the car?  Any pictures of where the wire goes to?

[jbrasile]

Casey, the a/c compressor is on the driver's side below the power steering pump.


In your case you have a Harrison R4. With the engine stopped, look at the pulley and you will see two male connectors sticking up, just plug the wire into it and turn on the a/c to see if the compressor works, you will hear it click when the clutch engages.

The plug is circled in this picture



Since you acc servo might be bad, turn on DEF which will always switch on the compressor, if it doesn't work then you need to investigate further.

Hope this helps.

Tks,

Joe

[1980sdga]

Hope this helps.  It plugs into the bottom of the compressor.  On Chevys they were mounted with the plug on the top. 

Ze Germans have mounting downside-up!!   I believe it's was a pretty solid R-12 compressor but mine was converted to R-134.  When it works it's awesome!  When it doesn't you get heat 

Hopefully yours will fire right up!  Just hope you don't have to do the vacuum leak, amp, servo boogie...

[Casey]

I found the plug - mine is on the side, not bottom, like the picture jbrasile posted.  I believe mine is still R12.  Only problem - I don't know which way to plug the connector in!!  There are two wires - red and green.  Which should go up?  I don't want to chance it and plug it in backwards.  Plus I still have a missing fuse that I don't know what to get to replace, which I think might be needed for this:



Can somebody clue me in on the fuse specs so I can pick one up at the auto parts store tomorrow morning?  And of course, which way the wire plugs in?

Bit by bit...thanks for all the help!

[Casey]

Casey, the a/c compressor is on the driver's side below the power steering pump.

Yep, it's the part I thought it was, and you seem to be right with the part ID (which is different from 1980sdga's!)

Since you acc servo might be bad, turn on DEF which will always switch on the compressor, if it doesn't work then you need to investigate further.

I currently hear a bunch of little ticks and clicks whenever I press any of the buttons on the ACC.  How do I identify the compressor click?  When you say engage the clutch, do you mean I need to shift the transmission into drive?  I also could test the voltage at the wire connector - should it be battery voltage?

[jbrasile]

Hi Casey, don't worry about which way the plug goes in, you can't really hurt anything, besides the wire is old and it will kind of position itself.

The clutch I am referring to is the compressor clutch, with the engine off and key in pos 2 (dash lights on) you should hear a click from the front of the compressor, that is the compressor's electro- magnetic clutch engaging.

The two in line fuses are for the radio, which should be fine since yours is working and the other one is for the acc, it is a 2 amp glass fuse as per the manual. Give it a try and see what happens.

Tks,

Joe