Low Coolant Light Trouble Shooting.

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diaric

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I'm putting my dash back together on my 87 6.2 Jimmy Restoration and I seem to have an issue with the low coolant sensor light not coming on.
Does anyone know how to troubleshoot the controller box for it?

I've tried searching around bit keep coming up empty. When I unplug the wire from the sensor in the rad, the light should come on from a signal loss, but I'm getting nothing.
The only odd thing I had previous, was when I put the batteries in a few months ago. The light stayed on steady, grounded sensor it not with the passenger battery installed. When I hooked up the drivers battery, it went out, but that battery just grounds to the block and chassis, no extra wiring.

Trying to get this sorted out so I can get the dash and cluster all back together for good before paint.

Thanks, Richard.
 

chengny

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I doubt you'll be able to fix the lamp driver (Low Coolant Switching Module). Pretty involved, unless you are familiar with board-level repairs.

For a start, just make sure all the leads (4) to the module are doing what they are supposed to:

1. PINK/BLK - module power supply - should be 12VDC (from the ignition bank of the fuse block)

2. BLK - main module ground - should have continuity to common ground bus

3. GRAY - warning lamp grounding leg - should have continuity from the warning lamp to pin "E" on the module

4. BLK/YEL - sensing leg - should have continuity to ground when the probe is submerged. Infinite resistance when not in contact with coolant.

Schematic with major components highlighted:

You must be registered for see images attach
 
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diaric

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Thank you very much.
When I find the little box. I'll test out the contacts and see what's up.
Hoping I accidently disconnected something when I was rewiring a ton of stuff under there.
 
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highdesertrange

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hey diaric nice to see you over here on this forum. I see you on that other forum all the time. so I know you got this figured out. highdesertranger
 

diaric

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hey diaric nice to see you over here on this forum. I see you on that other forum all the time. so I know you got this figured out. highdesertranger

Thanks, all solved.

Found the box, and with the help of the diagram, solved it, kinda. The power Y's off at the box directly to the bulb, guess what, no power . I went through every pink/black wire, every fuse, everything seemed fine. I don't know where pink/black 139 gets its power, but I didn't find it and don't know if I accidently screwed up the connection somewhere in my rewiring.

Didn't fix it correctly, but its fixed. Ran an ignition jumper over to the bulb, and it cycles perfectly with the key and comes on if I unplug the sensor.


thanks for the help
 

chengny

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That pink/black wire plugs directly into a socket in the the upper section of the fuse block. It would have one of those dedicated plugs that can only fit into a certain type of socket.

In this case it plugs into one of the "IGN" sockets - they are the sockets that form columns 3 & 4 from the left. But all that doesn't matter now - as long as you found a switched power supply
 

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