94 Cutlass Defroster wiring help - Need help getting wiring connector apart. Update and pics in post 4

[Leadfoot]

Earlier this year, my rear window defroster worked fine.  However, when it should cut off, the relay under the passenger side of the dash would make a loud buzzing noise.  I could manually turn the defroster off.  I replaced it with 2 new relays with the same result.  I briefly checked the wiring and relays under the dash, but didn't have time to dig deeper.  About 2 months ago the defroster stopped working altogether.

 

I finally had time today to dig into this more. I do not have power at the hot side (passenger side) of the rear defroster (purple wire from the relay).  I tested the defroster itself with a multimeter and it works fine.  I ran a jumper wire from the relay to the back window and the defroster worked.  The jumper wire got warm, but did not blow the 25amp fuse inline (smallest spare fuse I had).  I need to address the hot (purple) wire from the relay having a break in it, but did not get back to that yet.  I was concerned the ground side from the drivers side of the rear window might not have a good ground causing the warm jumper wire and possibly being the cause of the initial problems.  

 

I followed the ground wire all over the car while pulling seats and carpet to ensure I followed the correct wire (I could kill some GM engineers for running that wire back and forth across the car.  I traced it to a large connector right next to the parking brake pedal mounted to the kick panel.  I tested for continuity to verify this is indeed the same wire.  I then noticed the wire goes into the drivers door.  At this point I was out of time.  I cannot think of a reason why this wire would run into the drivers door.  The only possible idea I can come up with is that it triggers a heated mirror on the door?  I don't believe I have heated mirrors, but I could be wrong.  I plan to pull the door panel in the next couple of days to see if I can figure out what it is connected to and why it even runs into the door.  

 

Has anyone ever traced this wire?

 

I was considering cutting the wire in the trunk and grounding it good right there.  I believe depends on what else this wire connects to.  It seems that this wire would not run all around the car to the door if it could just be grounded in the trunk.  However, I have seen similarly foolish designs so I am not ruling it out.  

 

Any help or advice before digging deeper would be appreciated.

[ManicMechanic]

Unless you bought the car from Taylor, it does not have a heated mirror.

 

Those grounds run to a ground distribution which is why they go everywhere. I'm not entirely sure where they are located.

[rich_e777]

Sounds a lot like what happened/ happening with my 1994 CS, buzzing sound and all. My defroster button doesn't activate my defroster every time, like it doesn't "click" at the console. Then when it does I can only get it on for awhile before it shuts itself off. I still haven't fixed it as I`m in the middle of an interior project and need to pull the dash and will dig into it more then.

 

I`m about as far as you are at this point , Ive got all the seats and carpet pulled and had this exact thing to do on the list so I`ll post what I find as I find it. My FSM is at my shop so I don't have it with me but I`ll post what info it has about this circuit with the ground locations tomorrow, or later tonight if I get out I`ll run by and grab it.

[Leadfoot]

Ok, so an update.  I pulled the drivers door apart and its the ground for the switches on the drivers door.  Testing I had continuity to ground, but it was roughly 1 ohm.  I spliced a ground in the trunk to where the ground comes off the drivers side of the defroster.  Once I did this I had very good continuity to ground (0 ohm).  Once doing this I tackled finding the break in the hot side.  What I found was the big junction box near the kickpanel on the passenger side is where I lose power.  I have continuity of the purple wire, but its very poor (47 or 470 ohm.  Not OL, but bad and no power transfers through).  I tried to take this junction apart to check and see what the problem was as I assume it could become a problem with other wires making a connection there.  I could just wire around it for this particular wire, but would rather inspect all connections.  I could not get this apart for the life of me.  Am I missing something?  I am concerned the heat from the poor connection may have melted some of the plastic making it difficult to get apart, but it is entirely possible I am wrong.  Here are pics of what I am talking about.  

 

 

 

[Leadfoot]

I guess I should note that I did take the torx bolt in the middle out.  I am not that dumb.  

[Leadfoot]

Spent some time yesterday and just kept gently prying until the connector came apart.  The plastic right around the connector for the purple defroster wires was melted slightly which was causing it to stick.  Once I saw the condition of the connector, I realized that I needed to bypass this block for the defroster wire.  I tested all of the wires around it and all had good connection and continuity.  After cleaning it up and bypassing the defroster wire around it, I tested the defroster and it worked perfectly.  It stays on the proper amount of time, the window gets warm, and it shuts off with no buzzing or anything like that. 

 

While I had the seats out, I cleaned the carpets and am waiting for them to dry to finish reassembly.

 

Anyone having this problem, I would suggest checking for continuity from the defroster relay (purple wire) to the connector at the back window.  If you don't have good continuity check this large wire connector first.  This seems like it could be a problem area.

[Leadfoot]

Time for an update.  Once I put it all back together (wiring harnesses, etc tucked into the right places) I assumed all was fine.  Needed the defroster 2 days later in the morning and after 3 minutes the relay was buzzing again.  It has done this every time I have used it since.  I think the wire might have a bad spot somewhere that is affected when everything is put back into place (possible a bend that has gotten brittle or broken over the years).  As soon as I can find time, I am going just run a new wire and see if that fixes it.  At least the defroster comes on now, but it only works for a couple of minutes.  Progress, but I am not giving up.  I have too much work into it to give up now.  

[Leadfoot]

Ok, had a few minutes to mess with this over the weekend.  I took the under dash cover off and turned the defroster.  After roughly 2 minutes the buzzing started.  I reached to touch the defroster relay and verify that indeed was the buzzing.  In this process I touched the circuit breaker for the power to the defroster relay and it was really hot and nearly burned me from just brushing against it.  I have purchased a new breaker and need to put it in.  I am guessing it could be the result of a bad connection coming to the breaker and that the new breaker won't fix it.  Any thoughts?