Glowing orange paper clip

[TurboDonnie]

What in the world? Here's what happened. I was diagnosing a non lock up condition, checked the brake switch and it the switched worked fine, cruise works and disengages when the brake is applied so I assume the brake switch is working properly. But anyway........

I decided to force lock up with a paper clip. Put one end of the clip into pin A and the other end of the clip in pin F, here's where it gets strange. Almost immediatly the paper clip started turning a bright glowing orange, hot! I flipped the clip out and smoke was rolling. What happened? I've used the clip many times with my GN but never did something like this happened. Any ideas? Thanks

 

[kessler]

Re: Glowing orange paper clip

Uhm wow i dont know what to say, Maybe im not understanding but what are you trying to lock up? Converter????

 

[TurboDonnie]

Re: Glowing orange paper clip

Yeah the converter. It's not locking up so I was trying to force lock up with the paper clip.

 

[twin74s]

Re: Glowing orange paper clip

You have a short somewhere....

 

[kessler]

Re: Glowing orange paper clip

Did you try from the ECU Brown wire right?

 

[dgoodhue]

Re: Glowing orange paper clip

A is ground. If its glowing with F connected, it would seem that somehow F is powered. I would guess that the TCC solenoid in the transmission is short, its more of guess, though. I would follow the circuit around with a multimeter.

 

[sly dvl]

Re: Glowing orange paper clip

You have a short somewhere....

A short to power perhaps. A short to ground would blow a fuse as soon as the ECM tried to command lock-up.
I assume you've checked the fuses?

K

 

[TurboDonnie]

Re: Glowing orange paper clip

Yeah, I'll be interested as to what I find as well. You can imagine my surprise when I looked down and found my paper clip glowing like a filament bulb :dropjaw:

 

[sly dvl]

Re: Glowing orange paper clip

I agree: 'Short to power'. A short to ground, on the brown wire, should result in lock-up at all times, unless brake pedal depressed. Engine won't idle in gear; brake off. It would not cause a 'blown fuse', because the ECM applies a 'ground' to lock up TCC. The only fuse that should be in play is "brake".

Short to power: The ECM can't sink the TCC to ground. No TCC apply.

But what kind of short to power, that's un-fused ( the papercilp should have blown the fuse.)?

Interesting to know what you find....
DaveP

True, however, because the brown wire is now powered for some reason when the ECM tries to ground it (for TCC applied) whatever circuit is powering up the brown wire should blow a fuse. I'd double check your fuse ratings. The TCC is on your gauges fuse; 5A.

Also, there's a pressure switch in the transmission that prevents the TCC from engaging until 3rd gear. Not sure if it's on the + side or the - side of the solenoid though.

K

 

[TurboDonnie]

Re: Glowing orange paper clip

What do I need to check first? The brake lights come on when the pedal is pressed and goes out when the pedal is released and all of the gauges, interior lights, radio,etc works. Cruise control works just fine and disengages when the brake pedal is depressed just as it's supposed to. I am baffled to say the least.

 

[TurboDonnie]

Re: Glowing orange paper clip

The wiring diagrams in the back of the supplemental manual shows and in-line diode in the TCC wiring, is it possible that the diode has lost it's function? and if so, where in the crap would the diode be located?

 

[TurboDonnie]

Re: Glowing orange paper clip

Dave, Thank You so much :tup: I'm printing your info off now so I can check all of this out. I will post results when I have them.

 

[sly dvl]

Re: Glowing orange paper clip

There IS a Normally Closed switch in the B+ side of the solenoid, in the trans. It is called "4-3 downshift SW". It is opened during a 4-3 downshift. Probably to prevent "harshness", if the TCC remain engaged during the downshift. It CAN'T have anything to do with 'when' the TCC engages, as it is a 'normally closed' switch. Take a look at a 4L60 hydraulic schematic. It very clearly shows how this switch functions. (I just did :tup: )

The no TCC until 3rd gear, is a function of the ECM. It is not "hard wired" in the transmission.

Regards,
Dave P

Correct me if I'm wrong but is this not a 700R4 transmission?
When the TCC solenoid in my 700R4 went bad (89 S-15 w/4.3 - windings started to short) when I commanded it through the ALDL connector as soon as I hit 3rd gear it took out my gauges fuse.
The schematic I have shows the ppl. wire leading into the brake switch (N/C contacts) coming from the gauges fuse - 5A.
Then again, my schematic is not SyTy specific. Perhaps there's a difference?

 

[MAITAI1993]

Re: Glowing orange paper clip

I tried it im mine worked fine so short is it im sure. look at the brightside If you cant fix it take the paper clip coil it up and use it for an in car toaster just grab a english muffin and roll hot snack anytime. :tup:

 

[TurboDonnie]

Re: Glowing orange paper clip

Here are the results so far.

I unplugged the connector on the brake-light switch with the 1 purple and the 1 pink/white

Pink/White, voltage = 12 volts
Purple, voltage = 0

Brake fuse is good, which is a 15amp fuse

For giggles, I put the voltmeter to the ALDL port and with the probes in pin A and in Pin F and it read 12 volts, with the engine off key on it read 11 volts.

Do I still need to check the voltage at the trans with the trans connector unplugged? If so I'll have to do it tomorrow since I've run out of light and it's raining.

I've been trying to back track anything that I might have done to cause this. The only thing I can think of is I installed ny PLX DM100 and Vac/Boost modules, but it was pretty uneventful. The power for the modules goes to a +12v ign. source in which I used one of the acc. spots at the fuse box, the grounds just went to a chasis.

 

[TurboDonnie]

Re: Glowing orange paper clip

Okay, I checked the trans plug with it disconnected, the tan/white = 12v, the purple = 0. I didn't get to check them however with the brake switch connector disconnected. I will do that in a little while. I also didn't get to check it with the engine bulkhead disconnected, simply because I couldn't get it loose. I was afraid of breaking it. To verify, the engine bulkhead connector is outboard, under the hood just to the bottom right of the brake booster and is the one with the screw in it. Does that sound right?

 

[TurboDonnie]

Re: Glowing orange paper clip

I'll try and see if I can get it disconnected.

One thing I did do, with the voltmeter, I put the probes in A and Fat the ALDL, truck running, and it shows 12v and when I depress the the brake pedal it goes to 0. Does the same when I use a chasis ground. I'm going to a freinds shop in a little while to put my new Prime Gears front prop shaft in and I'll have him help me get that bulkhead connector loose.

I just don't understand why all of a sudden it to start doing this.

 

[sly dvl]

Re: Glowing orange paper clip

Hang on, that's what it's supposed to do. With 12v on the ppl wire going through your brake sw. and into your TCC, but no path to ground of course you'll get 12v on the F term at the ALDL. When you hit the brakes you remove the 12v from the ppl. wire - removing the12v from the circuit.

The question is why did your paper clip glow hot and why didn't it blow the fuse?
Sounds to me like your TCC Solenoid is completely shorted and there's no longer any "load" on that circuit, which would explain the glowing paper clip.

You need to measure the resistance of the solenoid. Easiest way would be to unplug the brake switch (make sure there's no power on it, Ign.off) and connect an ohmeter between the ppl. wire leaving the brake switch and the tan wire in the F term. I don't know the spec. but I think around 45 ohms should be decent. I'll bet your reading is much lower then that.

A quick "Google" search revealed a resistance reading of about 20 ohms.

 

[sly dvl]

Re: Glowing orange paper clip

Any update on this issue?

 

[TurboDonnie]

Re: Glowing orange paper clip

I am leaning toward the TCC solenoid being completely shorted out. I'm going to drop the pan this week and put a new one in. This has certainly been strange. There has been no other issues whatsoever, drivability has been flawless as well as every other electrical function. I'm hoping to get the pan dropped and the TCC changed out today or tomorrow depending on the weather.