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Trans Light on when the Run Switch is Off?

DHumvee

DHumvee

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I have an 1157 from GP I'm slowly going through and noticed that my Trans light stays on when the switch is OFF. When I switch to RUN, the light gets brighter. Any ideas?
Thanks in Advance!


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Mogman

Mogman

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That is an interesting thing that seems to happen often.
If you look at page 49 of the attached document you will see the trans. check light is only powered when the trans relay is closed, that is when the run switch is on.
I have not seen this personally so I have not had the opportunity to trouble shoot this.
I would be interested in what voltage is on pin U of the TCM and also what voltage is on wire 290/291 measured to ground with the run switch off.
There are two different 290/291s on each side of the transmission relay I am talking about the "switched" side of the relay.
Also step on the brake and see what the lamp does with the run switch off.
 

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86humv

86humv

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Relay will sometimes stick....with ignition off...go back to panel behind front right seat where relay is and pound on it...sometime relay will reset.
 
DHumvee

DHumvee

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Mogman said:
That is an interesting thing that seems to happen often.
If you look at page 49 of the attached document you will see the trans. check light is only powered when the trans relay is closed, that is when the run switch is on.
I have not seen this personally so I have not had the opportunity to trouble shoot this.
I would be interested in what voltage is on pin U of the TCM and also what voltage is on wire 290/291 measured to ground with the run switch off.
Click to expand...
I am still in the process of tracing wires that GP cut with a grinding wheel.
Mogman said:
That is an interesting thing that seems to happen often.
If you look at page 49 of the attached document you will see the trans. check light is only powered when the trans relay is closed, that is when the run switch is on.
I have not seen this personally so I have not had the opportunity to trouble shoot this.
I would be interested in what voltage is on pin U of the TCM and also what voltage is on wire 290/291 measured to ground with the run switch off.
There are two different 290/291s on each side of the transmission relay I am talking about the "switched" side of the relay.
Also step on the brake and see what the lamp does with the run switch off.
Click to expand...
That's better than really bad news I suppose. We just moved from Fl. to Al. , my tools aren't here yet. As soon as I can get my hands on a voltage meter I will respond. My first truck took forever to be released, this one only took two weeks. I had to get it picked up from GP before the Al. move was a done deal. That means I got to ship it twice! Thanks for your reply Sir.
 
DHumvee

DHumvee

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Northwest Florida
Mogman said:
That is an interesting thing that seems to happen often.
If you look at page 49 of the attached document you will see the trans. check light is only powered when the trans relay is closed, that is when the run switch is on.
I have not seen this personally so I have not had the opportunity to trouble shoot this.
I would be interested in what voltage is on pin U of the TCM and also what voltage is on wire 290/291 measured to ground with the run switch off.
There are two different 290/291s on each side of the transmission relay I am talking about the "switched" side of the relay.
Also step on the brake and see what the lamp does with the run switch off.
Click to expand...
86humv said:
The panel close to relay bolts...about in the middle.
Click to expand...
86humv said:
The panel close to relay bolts...about in the middle.
Click to expand...
The suspense was killing me so I opened the panel. What sticks? I want to thump it...

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DHumvee

DHumvee

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DHumvee said:
I am still in the process of tracing wires that GP cut with a grinding wheel.

That's better than really bad news I suppose. We just moved from Fl. to Al. , my tools aren't here yet. As soon as I can get my hands on a voltage meter I will respond. My first truck took forever to be released, this one only took two weeks. I had to get it picked up from GP before the Al. move was a done deal. That means I got to ship it twice! Thanks for your reply Sir.
Click to expand...
Update: I found my meter... I haven't had time to find the two wires 290/291 yet but 687 A and B (the indicator TRANS light wires) are getting 8.7 v all the time making the dimmer light and 11.6v when the run switch is ON for the brighter light. Ideas??
 
Mogman

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Both lamp wires are getting 8.7V as measured to ground?
EDIT and was that measured with the lamp plugged in?
 
TOBASH

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Just out of curiosity, are any 24 Volt systems getting voltage? If so, the problem is in your EESS or PCB. If not, then it is most likely the 12 V solenoid (unless you have a short circuit somewhere bypassing the relay).
 
DHumvee

DHumvee

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TOBASH said:
Just out of curiosity, are any 24 Volt systems getting voltage? If so, the problem is in your EESS or PCB. If not, then it is most likely the 12 V solenoid (unless you have a short circuit somewhere bypassing the relay).
Click to expand...
Everything is working but I have been chasing something that's making it run hot.
 
TOBASH

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DHumvee said:
Everything is working but I have been chasing something that's making it run hot.
Click to expand...
I should have been more specific. When the ignition is off, is there any 24Volt current flowing? If so, the PCB/EESS is sending power to the 12 V relay and the problem is the PCB not the 12V relay.
 
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Mogman

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OK, well that was not the information I was asking for, I'm sure you will get it figured out.
 
Retiredwarhorses

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You guys need to break out the schematic, the transmission and it’s associated components are all 12v, The input voltage at the Trans relay from the ignition is 24v, once 24v is presented, the relay closes, this forces the adjacent 12v relay to close and supply power to the TCM and Transmission lamp, it’s a civilian 12v GM transmission setup, nothing fancy.
 
DHumvee

DHumvee

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Northwest Florida
Mogman said:
That is an interesting thing that seems to happen often.
If you look at page 49 of the attached document you will see the trans. check light is only powered when the trans relay is closed, that is when the run switch is on.
I have not seen this personally so I have not had the opportunity to trouble shoot this.
I would be interested in what voltage is on pin U of the TCM and also what voltage is on wire 290/291 measured to ground with the run switch off.
There are two different 290/291s on each side of the transmission relay I am talking about the "switched" side of the relay.
Also step on the brake and see what the lamp does with the run switch off.
Click to expand...
Good Afternoon, I wanted to thank you for your response and help with my question about the trans light on my truck. I wasn't ignoring your advice, we were moving and I hadn't sat down in weeks long enough to figure out where those wires were located so I could check them. I am new to the hobby and eager to learn. Thanks again for your help.
I didn't know how to determine which was the switched side wires so I checked both.
- With the switch in the OFF position the top wire on the Reset button measured 12.6v and the bottom wire measured 0v. There is no change to the brightness of the trans light when you press the brake with or without the headlights lights turned on.
- The only time the light gets brighter is when you switch the Start Switch to the Run position (without starting it).
- The light goes OFF when the truck is running.

I look forward to hearing from you.
Dave
 
TOBASH

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If you can turn on your lights when the ignition is off, or operate the flashers, then you know.
 
DHumvee

DHumvee

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TOBASH said:
If you can turn on your lights when the ignition is off, or operate the flashers, then you know.
Click to expand...
They are working fine. I just saw another owner asking the exact same question (same symptoms) on one of the Face Book groups. Must be pretty common, Thank you guys for the help.
 
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