1987 Chevy Truck No current!

Tiny
CRESTA
  • MEMBER
  • 1987 CHEVROLET TRUCK
Electrical problem
1987 Chevy Truck V8 Two Wheel Drive Automatic

I have no SES light. I have done the diagnostics and have no 12v power to ECM terminals C16 and B1. (I do have power on A6).
I have checked ECM B fuse and it is OK however I do not have 12v at the fuse holder? Nor do I have Horn/Dome or Lights, tail and park. All these fuses are OK and are on the left side of the fuse box (Which is the Batt side which I think should be a permanent 12V). This is telling me that I may have a feed problem to the fuse box. Can anyone tell me where the feed is to the fuse box and what color wire should it be?
I have checked the wires from the convenience center and they are OK. I have also checked for 12v down line from the fusable link and that is OK (if it is the black lump in the wire from the convenience center!)!
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Tuesday, March 17th, 2009 AT 6:23 PM

5 Replies

Tiny
JAMES W.
  • MEMBER
The only fuseable links (2) that feed your fuse block come off the starter solenoid unless you have a factory dual battery system.
It sounds like most of your fuse block is dead. If it's not one of the links by the starter it must be in the fuse block itself. Pull it lose and check the backside for any burned areas. You should be able to see the power grid route from the back. Let me know what you find.
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Tuesday, March 17th, 2009 AT 11:55 PM
Tiny
CRESTA
  • MEMBER
Thank you for your reply.
I do have ignition power to fuse box along with accessory power, just no permanent batt power!
(I do not have the optional factory two batteries).
There are only two pos wires to/from the starter solenoid (not including the switch wire). One goes directly to the pos batt post (thick), the other goes to the convenience center (medium) neither appear to have a fusable link!
There is no apparent alteration to the wiring harness.
I do not have a wiring diagram but in supposition I think that the two wires that leave the convenience center are as follows. I medium thickness RED wire goes towards the passenger side and eventually terminates at a relay on the A/C evaporator.
The other is a medium thickness ORANGE wire with a black "lump" in it about 4 inches from the convenience center with the #16 on it. This is the wire I THINK maybe takes battery power via the big connector through the firewall to the fuse box.
I do have 12 volts in this wire about an inch down line of the "lump"
Are you able to confirm I am on the right track?
Thanks again,
Ric
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Wednesday, March 18th, 2009 AT 9:06 AM
Tiny
JAMES W.
  • MEMBER
Normally I can pull a power distribution diagram but, there isn't one available for your truck. The diagram I have shows 2 fused links off the starter.
You're on the right track. The wire with the "lump" in it. Do you have 12 volts on BOTH sides of the lump? If no, this is probably where the problem is. Let me know.
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Wednesday, March 18th, 2009 AT 9:54 PM
Tiny
CRESTA
  • MEMBER
Thanks for you help guys but I have found the problem! What was confusing to me was the second wire (with fusable link from the starter) was not there. From all the research I did it should have been. On the Diesel and I think 454ci this power lead went directly from the battery + to the alternator. It must have done with this one as well although it is a 350ci. I did find someone else on th internet with the same problem, sound like some may have come off the production line like this. When we got this truck it had no engine so we put a 92 TBI in it with some electical modifications but the pos battery cable was not with it so we used the one that came with the 92, this went straight to the convenience center. Truck is now up and running!
Thanks again,
Ric
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Thursday, March 19th, 2009 AT 7:45 AM
Tiny
JAMES W.
  • MEMBER
Glad you found it, Ric. Our resource system is usuallt pretty much right on but, there are some holes in it. Anything else, you know where to find us.
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Thursday, March 19th, 2009 AT 2:18 PM

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