Really stuck electrical system 70 Mach 1

callys · Aug 18, 2007

Hi everyone I have not posted in the classic section before, but I have always gotten some good info on this site in the 5.0 tech area.

A little while ago my grandfather gave me his 70 mach 1. Its a 4 barrel cleveland car, but I think the kind of stuff I am dealing with would be universal.

2 weeks ago I was driving the car around the block and the alternator light came on. I drove the car home, and thinking it was just a bad dummy light, disconnected the negative cable on the battery to keep it from draining. Well the other day I hooked it up to troubleshoot the problem, the regulator started buzzing, then all the power in the car went out. I don't have any lights and the car won't crank.

So I replaced the regulator. Still nothing. All the fuses are good inside.

When I jump the battery positive over to the other side of the metering block, the engine cranks. So I figured maybe the metering solenoid was stuck closed. I replaced that. Still no luck.

The metering block on the 70 is the 4 post style. There is a line on the positive battery side that runs inside the dash from the block. This line then connects to the fuse panel on a stud. There is no power at the stud. I disconnected both sides of the line and tested it to see if it was broken with leads. It is fine.

So I am guessing it is a grounding problem somewhere inside the car?

Is there a master fuse somewhere?

Any other ideas or things I should check?

Thanks for any help.

Chip

TOM B · Aug 19, 2007

I think what your calling the meter block is the starter solenoid on the right fender.
That said, the hot wire from the battery goes to the solenoid large stud and the other side large stud goes to the starter. The one small stud in the front of solenoid is the start wire from you ignition switch start position. when you turn the switch to start this wire should go hot and kick in the solenoid to turn the starter. The battery ground wire is connected to the engine block, check for being loose. also a ground wire from the back of block to the firewall needs to be checked, this is the ground that goes bad most of the time and will cause a no start no lights problem. There is also a ground on each headlight to the front radiator support.
If all that fails the check the fusable links, these are in wire fuses that look like a round black cylinder. They will burn out if overloaded, there are 2 of them in the wiring coming to the starter solenoid on the fender, if they are bas just replace them with a inline mini fuse, a 20 amp works fine.
One last thought is to check the wiring from the alternator to the regulator.
this harness runs under and through the lower radiator support and rubs through and burns up, had that problem many of times.

Really stuck electrical system 70 Mach 1

callys

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TOM B

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Really stuck electrical system 70 Mach 1

callys

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TOM B

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