I have no 12volts at the rear window. I've compared this to another cavalier so I know I should see 12 volts.
I searched this topic a few times in this forum and tried out a few suggested things to narrow down my problem.
I checked the green connector at the kick panel on the driver side and it's not burned or corroded. I measured the pins and some read 14v, 5 v etc. I have power going through the connector.
I haven't measured the grid yet, and I have tint on the rear window, so I'm really hoping its a voltage problem.
The yellow light comes on and the fuse is not blown.
My question is, I came accross a schematic from this post....
diagram of circuit
Where is this green connector in relation to the diagram?
If I am getting power to all of the pins on the green connector, will this mean that the defroster relay and switch are ok in the Hvac panel?
Does the path GO....fuse panel to hvac unit to green connector to rear glass?
Anyone offer some help?
Ryan1
no updates yet, hopefully someone can suggest something
Ryan1
Well, as there are no replies so far I'll try!
I would GUESS that the connector C204 is the one talked about. It is after the HVAC unit and before the defogger grid---(but see below) as the +12 volts goes in on pin C and out on pin E
(On my '93, although the connector is a different number, it is roughly up above the drivers feet under the carpet, Behind I/P near LH shroud)
So you should have supply going in, from the fuse, on pin C of Connector C204--then pin A HVAC panel---through closed timer relay contacts (in the HVAC panel)---out of the panel on pin D----pin E of connector C204 to the defogger grid.
Check pin/skt C (in) and E (out)
This is the point where the connector pins were overheating and had to be bypassed by a link.
The connector MAY not be green, some cars have had different colours.
Post back again with your progress-hope this helps a little
Alont
UPDATE:
I pulled apart the dash today and found the wiring harness that plugs into the rear defogger timer (has 8 pins) the purple wire was burnt. Also the plastic harness was melted on the purple wire only. I tried ot repair this using some 10Ga wire but it still was getting hot. I have opted to replace the harness with one i got from teh junk yard. I picked up a entire HVAC controller with the harness for $50 CDN. I will update more on Saturday when i actually do the repair.
Ryan1
Ryan
As you have the 8 pin connector disconnected at the rear of the defogger timer and you said:- [I tried ot repair this using some 10Ga wire but it still was getting hot.]
can you also (carefully) disconnect the purple wire at the grid/last connection before grid.
Now the supply wire should be isolated at both ends.
Then check with a meter, set to the highest resistance range, between one end of the disconnected wire and the chassis ground---the reading should be infinite/open.
If you have some sort of lower reading that purple wire could be shorting to ground before it reaches the defogger grid
I just would not expect a 10g wire to get hot with the normal draw of the defogger grid, as the chart in this link shows.
5mm/10awg at 25degC /77 deg F even the worst spec wire takes 65 amps continuously
http://www.littelfuse.co.jp/data/jp/Product_Catalogs/AUTOFUSEOLOGY.pdf
As you are replacing the timer and wiring the above may not be necessary but it would help to find out why the wire melted?
Alont
alont,
You make a good point about checking for a short to ground.
I am a little confused how I am checking the purple wire as a short to ground. How i understand it is, disconnect the purple wire from the timer circuit, and place the positive lead on the meter to the purple wire and the black lead to a chassis ground?
Is that right?
I have an extra timer circuit so i may replace it. I was thinking that maybe the timer circuit was shorting causing the draw to the wire.
what do you think?
Ryan1
I just reread your post talking about the purple wire. SO you are saying disconnect the timer circuit harness from the timer circuit, and then also disconnect the harness at that "green" connector and measure the resistance of the purple wire?
Is the green connector the "grid"
Can u explain further?
Ryan1
Hi Ryan
referring to Kardain's diagram, you have the link in your first post:-
I would GUESS that the connector C204 is the one talked about--the Green connector..the purple wire passes through it on pin E--see below.
At the bottom right of the Heater- A/c and Rear Defogger control Assembly (The timer circuit box) there is a Purple wire starting at C3-D (Connector C3, Pin D)---{This is the connector to the timer circuit box, which you have disconnected
the path is then--3PPl-293 (size 3 metric gauge cable, purple in colour, circuit #293)----E-C204(Pin E, connector C204)----3PPL-293----Pin A-C220[Now changes color]--3Black-293--A-C1 {Disconnect here, this is the grid connector positive}
you said [SO you are saying disconnect the timer circuit harness from the timer circuit,---YES
and then also disconnect the harness at that "green" connector{NO--at the grid] and measure the resistance of the purple wire?--YES--but to GROUND
[How i understand it is, disconnect the purple wire from the timer circuit, and place the positive lead on the meter to the purple wire and the black lead to a chassis ground?
Is that right?]--EXACTLY RIGHT--if the Purple wire/293 circuit is shorting to ground{like trapped or rubbing] your meter will read from the positive lead,through the wires centre copper conductors, through the broken/damaged insulation to ground and back via the black negative lead to the meter.
Metric gauge 3 = AWG 12, AWG 10=metric 5 for info
[I was thinking that maybe the timer circuit was shorting causing the draw to the wire.] No, I don't think so because, if it were the ORANGE supply wire Circuit#-1340--from the fuse would be the melting one or the fuse would have blown. If the purple wire is melted(we know it is) it has to be some overload anywhere on the purple wire up to the grid to cause it.
As a seperate check, disconnect the grid ground, G302 in Kardain's diagram and make sure the connector/ring terminal is "shiny" clean, as is the chassis surface to which it connects. Then reconnect the ground.
Alont
i am assuming that when you say "grid" you are referring to the "grid" on the rear window AKA defogger lines? That should have clued in by now lol.
Ryan1
Sometiems i jump the wire and it takes time for thigns to sink in, I now understand what you are saying about the "grid" and the connector. I will measure it now and post results
Ryan1
Final Update:
I disconnected the purple wire from the timer circuit and also from the rear window "grid". I measured from the "grid" connector to chassis ground. The measurement on my meter was infinite on all ranges.
I spliced in the new harness into the circuit and connected it to the timer circuit. I then ran the car for a while with the defroster on and touched the casing of the wires, mainly the purple and the orange. They were not hot, maybe slightly warm, due to what I believe is a result of the current travelling through them when the defroster is turned on. I let the circuit complete it's timed operation and while still touching the wires, they didn't get any warmer or hot like they were before. I do believe that my first repair to just replace the wiring in a melted harness and re-using an already burned pin was what probably contributed to me feeling a hot wire the initial time.
I am still using the original Hvac controller that was in my car, i didn't use the one I bought from the junk yard.
Ryan1
Thanks for posting the reply, good to hear it's fixed and that you now have a spare controller.
Agree with the burned pin theory.
That's some impressive building in your sig background
Alont
Alont, i hope that others will come across this post in the future and it will help them also.
Thanks for the help, you helped me understand the schematic and where I needed to go next.
The building is the back side of an old church
Ryan1
UPDATE:
Problem came back again.....same purple wore is burining.,....i will have to look at it again...
Ryan1
I will be working on this again tomorrow ot find the source of the problem. I will keep you updated.
Ryan1
Alont if you read this,
In the above diagram, (see link) what do the dashed lines mean in the schematic? I am refering to the ones connecting H to D and H to E? I know it's not a wire, i can't recall what those mean.
Ryan1
I have gone ahead and checked for resistance placing the positive lead on the purple wire at the harness and negative lead to the grid connector on the drivers side of the car where all the wiring for the defroster is running. I had continuity and my readings were 0 ohms. I didn't notice any fluctuations in my readings that could suggest a wire rubbing etc.
I also took the grid connector from the other side of the rear window and again connected the purple wire to the positive lead and the negative lead to the grid connector. When i did this i noticed an erratic reading bouncing from some 4 digit number to open etc. I am not sure but wonder if this is an issue.
Luckily, I have another cavalier to compare this against in the morning.
Alont if u read this what do u think is causing that purple wire to melt?
Ryan1
Update:
Here's what i have tried so far to chase down this problem:
-Replaced burned purple with new wire
-Replaced Timer module (circuit board) with another one
-Directly ran a new wire from the module to the rear grid
After doing all this the purple line still gets hot after only a few seconds of being active.
I have a 99 cav here so I started searching between the 2 looking for a problem. Heres what i did.
-Took second timer module and connected it to the 99's system. No hot wires, so that works fine.
-Connected my rear window grid to the 99's wiring, using my second timer module. No hot wires
-Connected 99's rear window grid to my wiring, Hot wires.
I even thought maybe the ground side of the rear window grid might be an issue, so i made a new ground. Still hot wires.
I even disconnected my remote starter, foglights so they had no power with the key ON and still hot wires.
At this point I'm lost. I am thinking the only thing i can do is take it to a auto electrical specialist to diagnose.
I will keep everyone updated.
Ryan1
hey ryan.
just saw this post now.
this is exactly what happened on my 98 4 door. the purple wire in the 8 pin connector was burnt and chared to hell. i went to the scrap yard and picked up a new timming circuit board and new harness. the original circuit board had a burn spot in it too.
i replaced the board and soldered in the new harness, which seems to have fixed the problem. i belive something ight have gotten inbetween the traces or some type of a bad connection that caused excessive current or heat build up.
all is well with my fix so far, though i would like to replace that entire part of the harness one day.
rob.
1997 RedR - ZedR
Ya, I thought it might be the board also, that's why I bought a spare. I think it's a different situation considering when I plugged in my new board to the 99 cavalier it didn't heat up at all. It only got warm in my car.
I'm not sure what to think.
Ryan1
well it seems this is a pretty common thing to happen now. seems if the wire doesnt burn in the foot well there by the fuse box, it will burn up by the HVAC controls.
1997 RedR - ZedR
Now that i think about it, maybe my problem could be the repairs made to the wireing. I soldered them but the Larger purple and orange ones were harder to solder so the connection might not be a good one. i am going to go buy butt connectors and connect the wires that way and test it again.
Ryan1
Hi Ryan, I rambled on in this, but I will post it all in case it gives you a new direction
[In the above diagram, (see link) what do the dashed lines mean in the schematic? I am referring to the ones connecting H to D and H to E? I know it's not a wire, i can't recall what those mean.]
They just mean that the Pins H and D are in the connector C3 as are A.B and E at the top of the Defogger Control
[I also took the grid connector from the other side of the rear window and again connected the purple wire to the positive lead and the negative lead to the grid connector. When i did this i noticed an erratic reading bouncing from some 4 digit number to open etc. I am not sure but wonder if this is an issue.] Just to clarify, were you connected from the Positive lead of the tester to the Purple wire at the harness which was connected to the drivers side of the heater "grid' and the Negative lead was connected to the Passenger side of the grid?
[Alont if u read this what do u think is causing that purple wire to melt?] It can only be a low resistance in that circuit--somehow the purple wire is carrying more current than it is designed to carry--you have already replaced it so the actual cable can not be the problem.
Whitegoose wrote [I believe something might have gotten in between the traces or some type of a bad connection that caused excessive current or heat build up.] It's something like this!
Stating the obvious:-
Took second timer module and connected it to the 99's system. No hot wires, so that works fine.--Second timer modules OK
-Connected my rear window grid to the 99's wiring, using my second timer module. No hot wires--Your grid is OK
-Connected 99's rear window grid to my wiring, Hot wires.--There is still something wrong in your wiring harness.
I you imagine the circuit like this:-
Simplest
+12volts-----------VVV(Heater Grid)VVVVVV----------Ground
Actual
+12volts---[](Connectors)--[](Timer Module)--------VVV(Heater Grid)VVVVVV----------Ground
As you know your heater grid is OK and you have a good Timer Module, you have checked the Ground point---It must be the connectors or something to do with them
You could you try this--connect a fused(Same rating as the normal supply) NEW wire(Same gauge as the original, directly from the battery(or a 12 volt supply/battery charger) to the grid and ground. This will bypass the Timer module and all the connectors in the circuit. Does the wire overheat ? It should not because you have already checked this by using the 99’s wiring.
As a coincidence I was working on one of my ‘93 2.2’s and I have installed a shorting switch across the input and output of the Timer Module to be able to bypass this. On the ‘93 the door locks are fed from the same fuse and I have now fed them from a separate fuse to eliminate the door lock circuit from the defogger.
Good Luck
Alont
well I cleaned up the connections like i said above, Tested it again and it still gets hot.
As stated earlier this i know....
Grid is ok,
Timer module is ok
So I guess it's something in the wiring that goes through the car on this circuit.
I can't see what could be causing this.
I am looking at the schematic and am thinking of maybe bypassing everything.
I wonder if one of those other wire's in that connector could be causing this low level resistance?
i could remove then one by one to see if they make a difference?
Any thoughts are appreciated
Ryan1
I just tried removing each wire on the harness one by one and testing to see if anything there is causing the wire NOT to get hot. The purple wire still gets hot even when only the Orange (12volts) the black (ground) and the brown (on/off switch) are left.
I don't think it's the ground wire as I cut the wire that is going to ground on the grid and simply grounded it to metal to see if that was the issue and yet it still made no difference.
What about the 30 Amp fuse being weak? Could that add more resistance to the line?
I even went as far to try a new relay for the heater, i swapped the AC and heater ones as they were the same part number. No difference.
Ryan1
