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IndyJimW

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Well the electric gremlins finally won today, my '87 is completely dead. :( I've been waiting for this to happen so I wouldn't have to chase all the little mystery problems. Before I dive into the wiring and start to cut open the factory harness does anyone know WHERE the sole power wire that comes off the starter solenoid and into the firewall electrical plug-in goes? The '87 Monte Carlo SS wiring diagram shows three 10 gauge wires supplying electrical power, I can't believe Avanti used ONE 10 gauge wire to supply power to the whole car! That explains the three jumpers on the fuse block necessary to power all the fuses. <_< After I get this figure out and repaired I’ll post info on how to upgrade ’87 wiring.

Jim

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Well the electric gremlins finally won today, my '87 is completely dead.

Wow .. that totally sucks. What were the events leading up to this? Just one day

you went out to start it, OR it was running and died and nothing?

Tom

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Wow .. that totally sucks. What were the events leading up to this? Just one day

you went out to start it, OR it was running and died and nothing?

Tom

Its my daily driver and I've had electrical problems that come and go, never long enough or serious enough to dig into. Was driving around town for a couple of hours and stopped for lunch, came back out and car was completely dead. :o Had a test light and a volt meter with me, so I started looking. Power into and out of firewall plug, but no juice anywhere else. Ignition switch dead, fuse block dead etc. <_< Problem will be easy to fix just need a wiring diagram to help me,(Come on Ernest, THANK YOU!! THANK YOU!! THANK YOU!! :lol: ) I don't want to cut open the entire harness to trace that power supply wire, but it wouldn't be the first time.

Jim

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I don't want to cut open the entire harness to trace that power supply wire, but it wouldn't be the first time.

I am not sure how sensitive they get, but I got a spark plug wire tester from Walmart, that would

glow when near an electrical field. If something was made that could "sense" 12 volts then that

would work nicely to see where the power "ends". I know that the early cars used some circuit

breakers inline. I wonder if Avanti motors did the same??

Tom

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>snip<

Power into and out of firewall plug, but no juice anywhere else. Ignition switch dead, fuse block dead etc. >snip<

Not that I know anything about an '87, but here's some thoughts...

When you say there is power into and out of the firewall plug, do you mean you have power on both sides of the firewall? (eg, on both sides of the assembled male & female firewall plugs)... the earlier cars did not have a firewall connector, the harness passed through the firewall.

Have you separated the firewall plug to check for corrosion in the connectors? Considering that the body is essentially the same, I'm not surprised that there's only one 10 gauge wire supplying power to the body at the firewall, since that's the way it was done on the early cars, except it was a single 12 gauge (black) wire. I have a booklet with a 1981 wiring diagram that shows that wire as a red wire (probably 12 gauge, with a 14 gauge fusible link at the starter solenoid) that runs to the ammeter and exits the ammeter as a white wire with red trailer to connect to the horn relay and then the fuse panel and then the ignition switch and on to the alternator BAT connector

Is it not possible to trace the wire from the firewall plug to the fusebox to find out where you are losing the connection... I understand that you'd have to open the cable sheathing to check the length of the wire, but it must terminate at the fusebox, so there must be a way to check it where it attaches to the fusebox, and the distance from the firewall to the fusebox cannot be great. You could always run a long test wire from the solenoid directly to the fuse box, bypassing the harness, just to see if that main power wire is the issue, or if ground connections or some other issue is causing the problem... if the power wire IS the problem, and the connections are secure at the solenoid, the firewall plug, and the firewall, then you can either install a permanent bypass wire, or open the harness to find the problem.

Another thought is to check that the battery ground cable connections are clean and tight.

Edited by WayneC

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I dived into the wiring today and found the problem and definitely don’t like what I found. The wire that supplies ALL THE CURRENT to the car goes from the battery cable post on the starter solenoid, up to the firewall plug-in, into the harness and then thru a circular plug-in to the AMP METER back thru the circular plug-in and then to the rest of the car.

The circular plug-in was the problem, with a bad connection. It is located behind the center console about where the driver’s right knee would be, it is 1 ½” in diameter with a screw collar that holds it together. The plug-in has 2 large connectors and 16 small connectors. Power goes thru one of the large connectors up to the AMP meter and back thru the other large connector to power the car.

I thought it was strange that the car was completely dead after driving it all day, I found out why, after starting the car if you unplug the circular connector the car will continue to run on the alternator until you shut it down. Then the car is completely dead.

If your Avanti is wired this way you can test it easily by unplugging one of the large press on wire clips at the AMP meter, it will create the same problem. The car will not start and you will not have battery or ignition power to the fuse block. I don’t like this setup because all the current from the alternator goes thru the wiring harness in the dash then to the battery. I also what my fuse block to get current first.

Jim Wood

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the earlier cars did not have a firewall connector, the harness passed through the firewall.

My '87 uses a firewall plug just like the newer cars.

Have you separated the firewall plug to check for corrosion in the connectors? Considering that the body is essentially the same, I'm not surprised that there's only one 10 gauge wire supplying power to the body at the firewall, since that's the way it was done on the early cars, except it was a single 12 gauge (black) wire. I have a booklet with a 1981 wiring diagram that shows that wire as a red wire (probably 12 gauge, with a 14 gauge fusible link at the starter solenoid) that runs to the ammeter and exits the ammeter as a white wire with red trailer to connect to the horn relay and then the fuse panel and then the ignition switch and on to the alternator BAT connector

Separated firewall plug first, was suprised not to find a problem there. Not sure where wire goes from the amp meter, but I'll check the horn relay. Hoping to get a wiring diagram soon.

My chassis is a Monte Carlo and uses all the same electrical, Chevrolet uses 3 supply wires because of the load so I will probably do some rewiring. I have plenty of spaces on the firewall plug. I'm thinking of installing a fuse block also because the main wire doesn't look like a fusable link.

Sorry, I didn't see your reply before my last post.

By the way I'm an ASE Master Truck and Master Auto mechanic with 30 years experience and my own shop. I'm just having fun with my Avanti and welcome any help or comments.

Jim

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My '87 uses a firewall plug just like the newer cars.

>snip<

By the way I'm an ASE Master Truck and Master Auto mechanic with 30 years experience and my own shop. I'm just having fun with my Avanti and welcome any help or comments.

Jim

When I said early, I meant Studebaker and early Avanti II.

Considering your vast expertise, I feel silly to have replied at all.

How about creating a wiring diagram for your 87 and submitting it

to the AOAI magazine so others can gain from your experience?

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When I said early, I meant Studebaker and early Avanti II.

Understood. :)

Considering your vast expertise, I feel silly to have replied at all.

Your reply about the '81 wiring was very helpful, I'm know the wire coming off the amp meter is white, so now I'll know to look at the horn relay. ;) Thank you.

How about creating a wiring diagram for your 87 and submitting it

to the AOAI magazine so others can gain from your experience?

Mr Earnest Edwards is making copies of his '87 Avanti wiring diagram. Thank you Earnest.

I have been making alot of posts since I purchased my Avanti a year and a half ago and I just wanted the members to know that I have some experience and am not just yapping. I know enough to be very, very dangerous :D , and I value everyone's advise.

Some of the projects I have planned with pictures;

Front air damn.

GM serpentine belt kit for small block chevy.

Rebuid door hinges.

Install new window rubber and felt.

Rear disc brakes.

Have the parts for most of these projects just need to get off my dead rear end and install them. <_<

Would love to help anyone with keeping their Avanti on the road, or improving them.

Jim

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I recieved a copy of the '87 Avanti factory wiring from Mr Edwards a couple of weeks ago.

Thank you Mr Edwards. :D

About two-thirds of the manual are copies of the Chevrolet Monte Carlo wiring diagram with the other third showing some wiring and optional equipment installed in the Avanti. It is quite helpful for showing how all of the computer controls and relays are wired in, BUT is wrong on some of the major wiring. It shows three hot wires coming off of the starter, not one, and doesn't show an AMP gauge at all since the Chevy didn't use one. Since the single hot supply wire goes to the AMP gauge first in the '87 Avanti this is a problem. A loose connection at the plugin for the Television/Rear Head Phone Cut-Out Switch was the problem. I have wired around the plugin for now until I can decide how to rewire. I will try to draw a correct diagram.

Thanks WayneC for starting me in the right direction. ;)

Jim

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