Couple of electrical questions

eaglecap · Dec 17, 2007

I finished rebuilding a 75 Silver Ghia last year. I purchased it new
in 1975. It sat for over ten years before the rebuild and now has
about 6000 miles after. I did a total rebuild on 2.8L V6 and the 4
speed tranny. New alternator, starter, PS unit, brakes, etc. you name
it I replaced it. Total cost was twice what the car cost new.

1. Anyone know the purpose of the grounding strap that runs from the
transmission to the cross support under the tranny. Can't figure out
why this ground is necessary.

2. Since the rebuild I have had a few minor issues that seem to
be related to the electrical system. When the car is idling with the
lights on they seem to flicker like the juice is rising and falling or there is a bad ground. I replaced the alternator a second time with no help and rechecked the ground connections. Also the starter very intermittently will just spin and not kick in, like it may not have a good ground or enough juice. If I try it two or three times it finally catches and goes. Wonder it this is a starter problem, solenoid, or an elusive ground problem. I checked all the connections and found nothing wrong. The battery cables are new and the posts look good.

I am wondering if I am unaware of another grounding point other than the one on the firewall and the engine.

itsaMustangtoo · Dec 17, 2007

Your starter problem sounds to be a bendix. Easy to replace and not expensive either. As far as the lights flickering at idle. I had a 74 that did this alot. The lights also dimmed at idle and brightened when the rpm's came up. Since the wiring had been hacked up under the hood due to a v-8 swap I chalked it up to resistance. I suspect if you skinned the insulation off of the wiring you would see the corrosion and resistance I am speaking of. As long as you have a good ground from motor to chassis and all of the other small grounds are clean and tight the only other place I would look is the connection @ the firewall. Take this connection apart ( 3/8 " bolt) and make sure it is not corroded inside and tight as well. You say you replaced the alt but what about the regulator? I do not know what the gnd to the trans is for. Maybe someone else can shed some light on this for you and I as well. LMK how you make out. My 77 cobra I have now only dims ever so slightly at idle but all else is fine , no flickers etc.

Power Surge · Dec 17, 2007

Sure sounds like a poor engine to body ground. That extra strap on the trans may have been Ford's suppliment to the problem you are having.

I had the same two issues you are having, on two seperate vehicles. On my old 76 Cobra II, I had the starter issue. Turned out, there was NO engine to body ground on the car. Added one, and that solved that. Second car was a customer's 98 Lincoln LSC that I did a custom blower install on. I also had the alternator powdercoated and rebuilt. His car had the light flickering. He also had inadequate engine to body grounding. Added a nice heavy braided stainless strap, and no more problem.

The factory II negative battery cable goes from the battery, to the engine head, to the firewall. It's a crappy ground to the body. You should add a nice heavy ground cable from the engine block, to somewhere on the frame rails.

eaglecap · Dec 18, 2007

As to bendix, it is a new starter, suppose it could be the problem but felt I should check out the electrical first. Like maybe a new solenoid. Maybe it has some corrosion on the contacts.

Grounds--I think I will add a new ground from engine to chasis as suggested. The interior lights when on flicker just like the headlights so I am guessing ground not individual wire corrosion. The firewall connection was burnished well when I put the thing back together and I have checked it twice.

Will be after Xmas, will let you know. Thanks

itsaMustangtoo · Dec 19, 2007

eaglecap said:
As to bendix, it is a new starter, suppose it could be the problem but felt I should check out the electrical first. Like maybe a new solenoid. Thanks

I see, you feel as though you are not getting full voltage to the starter when you turn the key. Which very well could be a solenoid, But, if it does start and only misses engagement occasionally I would still say bendix. New starter,get an exchange on it. First though check voltage accross solenoid and resistance in the cable to the starter.

Wart · Dec 19, 2007

eaglecap said:
1. Anyone know the purpose of the grounding strap that runs from the
transmission to the cross support under the tranny. Can't figure out
why this ground is necessary.

Short answer: electricity is funny.

2. ....... Also the starter very intermittently will just spin and not kick in, like it may not have a good ground or enough juice. If I try it two or three times it finally catches and goes. Wonder it this is a starter problem, solenoid, or an elusive ground problem.

Probably none of them.

In the Ford starters of our era one field core is attached to the bendix actuation arm, and it's field coil is shorted. When power is applied to the starter the shorted field coil pulls the field core into the field coil thus engaging the bendix in the flywheel. When the core and arm travel a sufficient distance the arm opens a switch which de-shorts the system and allows current to flow through the starter motor.

If the switch the bendix actuation arm opens is corroded, pitted, charred, and so forth, the field coil does not short to ground so the field coil does not make a powerful enough electromagnet to pull the field core into the coil, the bendix does not engage and the starter only spins.

If this is the problem you can run a ground strap directly to the starter and it will make little difference.

If you have a good battery, all connections are correct, and the motor/bendix aren't making funny rattle bang chatter noises look at that switch inside the starter.

Stang2Man · Dec 24, 2007

I've got a few questions that kinda go in hand with this discussion. On my 78 Cobra I had problems with the starter after she got warm not starting back up. So I replaced the starter a few months back, since I drive the Expedtion or the wife's 05 I dont' get a chance to play with the II's as much. So I got back out the other day after it finally quit raining and tried to jump it, of course the car was cold and acts just like it does when it's hot and trying to turn over. Just to check some things out I popped the hood on my Ghia and the solenoid is wired to opposite to what the Cobra was, positive/negative were on opposite sides on each car. Which side of the solenoid is supposed to be the negative side? I got a feeling the Ghia was correct with with the negative towards the front and the positive towards the back. Can anyone verify this or does it even matter. Reason I got to looking at it though was to see how the grounds were run on each of the two cars cuz I thought my Cobra may just have a ground problem. I think I got a bunch of problems on the Cobra straighten out.

eaglecap · Jan 16, 2008

Final resolution

I told you I would get back with the fix. I put the Tx ground strap on with no effect on the light flicker or starter. Had the alternator checked for bad diodes etc, all is good. Rechecked all grounds and burnished up the firewall connection. No changes to the filicker or the starter problem. Might have to live with the flicker, only thing left I can figure is the regulator so will check that out.....

The starter problem was a defective new starter. Not the bendix switch but an intermittent internal short of some kind. I took it out and checked it out on the bench. The switch points looked good but the commutator segments looked like they had been coated with some kind of sticky black goo. When it failed on the bench to kick in there was a lot of arcing at the brushes even though it was spinning. When it did kick in there was still way too much arcing. Swapped in another new (rebuilt) starter, after checking it out on the bench, and all is well.

MUSTANG J · Jan 17, 2008

New means un-tested

MUSTANG J · Jan 17, 2008

Stang2Man said:
I've got a few questions that kinda go in hand with this discussion. On my 78 Cobra I had problems with the starter after she got warm not starting back up. So I replaced the starter a few months back, since I drive the Expedtion or the wife's 05 I dont' get a chance to play with the II's as much. So I got back out the other day after it finally quit raining and tried to jump it, of course the car was cold and acts just like it does when it's hot and trying to turn over. Just to check some things out I popped the hood on my Ghia and the solenoid is wired to opposite to what the Cobra was, positive/negative were on opposite sides on each car. Which side of the solenoid is supposed to be the negative side? I got a feeling the Ghia was correct with with the negative towards the front and the positive towards the back. Can anyone verify this or does it even matter. Reason I got to looking at it though was to see how the grounds were run on each of the two cars cuz I thought my Cobra may just have a ground problem. I think I got a bunch of problems on the Cobra straighten out.

One side of the solinoid leads to the starter (+) the other side of the solinoid leads to the battery (+). I don't think it would mater what side each was bolted to. (-) for the solinoid is the screws holding it to the car, and (-) of the starter is your engine / transmission which are grounded to your cars unibody.

Wart · Jan 18, 2008

eaglecap said:
I told you I would get back with the fix. I put the Tx ground strap on with no effect on the light flicker or starter. Had the alternator checked for bad diodes etc, all is good. Rechecked all grounds and burnished up the firewall connection. No changes to the filicker or the starter problem. Might have to live with the flicker, only thing left I can figure is the regulator so will check that out.....

I remember seeing several cycling/ pulsing lights back in the day.

Reaching way back into my memory ... spooky thing .... I believe Ford went from a electro-mechanical regulator system in .. ? .. 78? .. IIRC the old and the new can't, or shouldn't, be mixed. You may be running a new alternator with an old style regulator.?

The starter problem was a defective new starter. .... The switch points looked good but the commutator segments looked like they had been coated with some kind of sticky black goo.

That's a good one, motors with new brushes are suppose to be ran with a brush break in compound. After the brushes are 'set' the compound is suppose to be washed out. Seems like someone forgot to do that final step. Or mayhaps they had a squeaky set and greased them. ... LOL

When it failed on the bench to kick in there was a lot of arcing at the brushes even though it was spinning. When it did kick in there was still way too much arcing.

Your black gunk was keeping the brushes from making good contact with the commutator.

Swapped in another new (rebuilt) starter, after checking it out on the bench, and all is well.

Last time I went starter shopping I took a screwdriver. Pulled the shield and cover to inspect the electricals and movable field core. One 'parts house' had a starter with brushes firmly jammed in their holders with blast abrasive.

MUSTANG J said:
New means un-tested

Yep.

Used parts are proven parts. They worked all the way to the accident.

MUSTANG J said:
One side of the solinoid leads to the starter (+) the other side of the solinoid leads to the battery (+). I don't think it would mater what side each was bolted to.

Probably does not matter at all.

I have seen the Ford style solenoid with the housing about the main terminals marked but then the Ford style remote solenoid has found it's way into numerous applications. I guess what I have seen was the use of generic housings.

Unless your using a 4 terminal solenoid on a points ignition it probably does not matter at all which side the battery goes to.

MUSTANG J · Jan 18, 2008

MadMark said:
I remember seeing several cycling/ pulsing lights back in the day.

Reaching way back into my memory ... spooky thing .... I believe Ford went from a electro-mechanical regulator system in .. ? .. 78? .. IIRC the old and the new can't, or shouldn't, be mixed. You may be running a new alternator with an old style regulator.?

True dat ^ The early II's had the old electromagnetic regulator. My 1974 Mach 1 had one, I thought the 1975 had the electonic one but It can be swaped for the electronic unit. (they have the same plug) If the electromagnetic unit sits, it can cause the problems mentioned. (dirty corroded connections). The top comes off the electromagnetic unit. The contacts can be cleaned. You can adjust the voltage on the old ones (with a screw) as well! As much fun as that sounds, I would pitch it, and put the Electronic one on. (they are more reliable and don't create as much electrical noise). The Electromagnetic one is about 3" tall and the electronic one is about 2" tall. (So you can tell them apart)

eaglecap · Jan 23, 2008

All fixed

New voltage regulator fixed the light flicker problem.

MUSTANG J · Jan 24, 2008

Did it have the electomagnetic type (tall) on the electronic regulator?

eaglecap · Jan 24, 2008

Regulator Type & BTW

I replaced the mechanical type that was installed with a new electronic model.

By the Way, several months ago I posted a problem about my Tach which I also thought may be a ground issue. If I turned on my heater/AC blower while driving the tach indication would change. The higher the blower setting the higher the tach change. At 70 the reading was 35 with blower off and 40 with it on high. The new regulator fixed that problem as well.

Couple of electrical questions

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