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Wiring nightmare.

J

jimmysjimmy

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Hey everyone Im looking for some help here. I have a 90 gmc jimmy. I just put a 454 in it and converted it to carburetor. My problem now is that I have no headlights or turn signals. I have grounded the battery to the frame and the engine. Grounded the engine to the frame and the body. Hooked up the grounds in the harness to either the engine or the body. Core support has grounds to the frame and to the core support for the light harness. Im at a loss here.
 
Headlight get power from fuseable link at starter. Passes through headlamp switch then to brite switch through bulkhead connector and finally the head lamps.

Turnsignals are igniton switch hot to fuse, flasher in panel, turnsignal switch, bulkhead connector then to lights front and rear.

The two systems are separate, except they both may be powered by the same fuse link. Normally there 2 fuse links could be 3. Ignition switch should have at least 2 heavy guage wires that are hot all the time
 
I also switched to a 1 wire alternator. When I put the original wire to the alternator back on it while I have 12v power going to it thats the only time my lights will come on but its obviously not right cause my electric water pump and fans will kick on too but thats only supposed to be wired when the key turns on
 
There's 1 going from the battery to the alternator. If I touch the original alternator wire to it while it has power thats when the lights will turn on and the pump and fans kick on. If I take that 12v from the battery off the alternator then it has nothing. Won't even start
 
So your electric water pump and fans worked correctly (switched 12v) before you started rewiring for the new carb’d engine?

Are you using the original TBI wiring harness and, if so, have you deleted any wiring? If needed, I have diagrams for 91 which should be the same.

When you touch the original wire to power and the headlights come on, is the headlight switch on or are they coming on incorrectly?
 
The main power tie in the truck is supposed to be the starter motor + terminal. The battery connects there, as does the alternator, and the fusible links. If you drop one of the links, you lose like half of the truck.

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Its a whole new setup, new alternator, electric fans and new electric water pump. When i touch power to it the lights come on correctly as the switch is pulled out. Im running off the original wiring setup
 
Right now I have the main battery wire ran to the starter along with the 2 wires that were originally on the starter as well
 
One of the fuse links I mentioned in an earlier post powers the alternator, along with head lights and a few other things.
Head lights working with original alt batt wire connected tells me that either the fuse link is blown , or not connected correctly. I am thinking there should be 4 wires at starter. 1 batt cable, 2 fuse links, and crank signal wire.

The fans and water pump are a separate issue. Either power is being supplied by wrong circuit, or you have a short to power on that circuit.
 
So do you think I should have a power wire from the battery to the alternator along with the original wire that was on the alternator that has a fusible link in it? Or is that fusible link supposed to go to the starter?
 
jimmysjimmy said:
So do you think I should have a power wire from the battery to the alternator along with the original wire that was on the alternator that has a fusible link in it? Or is that fusible link supposed to go to the starter?
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The fusible link usually goes to the starter.
I prefer having it at the battery personally
 
I figured it out. Im going to start off with saying damn I feel stupid. I had my water pump and fans hooked up on constant 12v power instead of ignition power some how. Guess when I first checked it I didnt have the alternator wire hooked up so thats why it made sense at the time. I moved that and everything works as it should. Thank you for all your support and knowledge. Now time to button things up and get this ol girl back on the road. If ypu want to check it out its on jtcustombuilds on YouTube! Thanks guys!
 
jimmysjimmy said:
If ypu want to check it out it’s on jtcustombuilds on YouTube! Thanks guys!
Click to expand...

Sub’d, it’s always good to have another square body channel.

I fought I wiring gremlin on my Blazer for a while, the best thing I did was buying a PowerProbe. That thing found my issue in less than an hour.
 
jimmysjimmy said:
I figured it out. Im going to start off with saying damn I feel stupid. I had my water pump and fans hooked up on constant 12v power instead of ignition power some how. Guess when I first checked it I didnt have the alternator wire hooked up so thats why it made sense at the time. I moved that and everything works as it should. Thank you for all your support and knowledge. Now time to button things up and get this ol girl back on the road. If ypu want to check it out its on jtcustombuilds on YouTube! Thanks guys!
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Glad you got it, but you still have and issue. The original alt batt wire should be hot with out your additional hot lead from battery. Your extra batt /alt cable is back feeding the original alt circuit, headlights, and half the ignition switch. I do hope the new batt/alt cable has some sort of circuit protection, fuse, fuse link, circuit breaker. I suspect the original alt circuit fuse link is blown and should be replaced. Nothing wrong with having a second feed to/from batt to alt, esp if you have up sized the alt amperage
 
Wes Harden said:
Glad you got it, but you still have and issue. The original alt batt wire should be hot with out your additional hot lead from battery. Your extra batt /alt cable is back feeding the original alt circuit, headlights, and half the ignition switch. I do hope the new batt/alt cable has some sort of circuit protection, fuse, fuse link, circuit breaker. I suspect the original alt circuit fuse link is blown and should be replaced. Nothing wrong with having a second feed to/from batt to alt, esp if you have up sized the alt amperage
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I have a fusible link in that wire as well, I will be getting a new one for the alternator just cause its old and looks crappy anyways. Thank you for all your information sir I greatly appreciate it.
 
jimmysjimmy said:
I had my water pump and fans hooked up on constant 12v power instead of ignition power some how.
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If you can avoid running high power stuff from the ignition switch, it will last longer. Your pump may be fine, but engine fans can draw a lot of current. Best to route a thermostat to a relay and then draw power from an underhood, more direct source.
Blue85 said:
How did you wire your relays?
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This is why I lurk here. I wanted something older than my 96 Express cargo van. But.. it just fell into my lap. Electrical can be a PITA. This van fills a big gap in retirement. It's good to know the knowledge for whatever it may need comes with my cell phone subscription. 2Cav
 
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