Before any voltage issues / electrical issues Replace those 3 Groundstraps first!

[Hotshot]

I just wanted a share a very overlooked issue that’s so often over looked and will solve you electrical wows. GROUNDS!!!!

Most 911s have 3 ground straps, I’ll bet if you haven’t changed them, or think they look ok, they are not. This is also a time I went to the local box auto store and used a new cable for 2 of them. You can’t see them and they are better than Porsches. In fact if you look at the classic retrofit guys, it’s the same 1AWG wire they supply.

New Neg Battery to front ground strap - 1AWG.

New Porsche or Uro Chasis to gearbox Strap ( the flat one )

And most overlooked because it hides, New 1AWG strap from Alt to top of block.

I had replaced every strap, working system, and cleaned every ground / fuse point to a shine, and still had over voltage issues. Why?? Because I missed the 36 year old Alt strap. Look in the pic how corroded it was. And it’s small. I tested it with a meter and it was bad. Inside it’s toast. Get a new one. Preferablya 1AWG Clean those terminals.

Along with a new Alt ( not rebuilt ) from Valeo and VR, I’m Finally free of issues. 13.9-14.4 like a champ.

The VR sends over voltage to ground. You want that path clean.

I also decided to glass bead my fan to raw magnesium, clear cerakote it, and yellow zinc the fan strap and bolts, and clear cerakote them too. Happy with result, will never get dirty or oxides again.

For those SC and earlier folks, make sure to leave a non coated part of the fan shroud as it’s a ground point.








Look how bad my hidden bolts were oxidized. Rest assured they are all shiny now and that strap is long gone. So annoyed I missed that one before. The wires was awful too on the test bench.

[hienz]

Originally Posted by Hotshot

I just wanted a share a very overlooked issue that’s so often over looked and will solve you electrical wows. GROUNDS!!!!

Most 911s have 3 ground straps, I’ll bet if you haven’t changed them, or think they look ok, they are not. This is also a time I went to the local box auto store and used a new cable for 2 of them. You can’t see them and they are better than Porsches. In fact if you look at the classic retrofit guys, it’s the same 1AWG wire they supply.

New Neg Battery to front ground strap - 1AWG.

New Porsche or Uro Chasis to gearbox Strap ( the flat one )

And most overlooked because it hides, New 1AWG strap from Alt to top of block.

I had replaced every strap, working system, and cleaned every ground / fuse point to a shine, and still had over voltage issues. Why?? Because I missed the 36 year old Alt strap. Look in the pic how corroded it was. And it’s small. I tested it with a meter and it was bad. Inside it’s toast. Get a new one. Preferablya 1AWG Clean those terminals.

Along with a new Alt ( not rebuilt ) from Valeo and VR, I’m Finally free of issues. 13.9-14.4 like a champ.

The VR sends over voltage to ground. You want that path clean.

I also decided to glass bead my fan to raw magnesium, clear cerakote it, and yellow zinc the fan strap and bolts, and clear cerakote them too. Happy with result, will never get dirty or oxides again.

For those SC and earlier folks, make sure to leave a non coated part of the fan shroud as it’s a ground point.








Look how bad my hidden bolts were oxidized. Rest assured they are all shiny now and that strap is long gone. So annoyed I missed that one before. The wires was awful too on the test bench.

That ground strap is not the correct one for engine strap. Must be a flat ground strap.

[wazzz]

That ground wire is indeed the original one that connects alt. negative to engine block.

Then there are flat straps that connect block and trans to chassis. And a round wire that connects chassis to battery negative.

[GH85Carrera]

Little doubt the vast majority of electrical problems on cars are from faulty or weak grounds.

One absolute, you simply can NOT have too good of a ground. Like having too much money or too much horse power, it can't happen to you. When in doubt, check the grounds.

[Hotshot]

Originally Posted by hienz

That ground strap is not the correct one for engine strap. Must be a flat ground strap.

Check the part manual. That’s the ground wire. From the Alt to the top of the block is not a copper strap OEM.

[911obgyn]

There is another one on the 3.2 from intake manifold to chassis on the left side.

[Hotshot]

Originally Posted by 911obgyn

There is another one on the 3.2 from intake manifold to chassis on the left side.

Yes, that’s a grounding point. I was referring to the straps. Parts manual only states 3.

The electrical diagrams show all the ground points and I highly suggest folks clean them all up. I like a micro dermal with a brass wire brush and eye protection.

[917_Langheck]

Same alty ground wire - '84 3.2 Carrera

A good ground wire can be flat, or round, but should fit the need. The flat straps used on Porsche are ultra flexible and high current capable, but a round wire with the same properties could be used. The only "must" that need to be obeyed are the laws of electrical physics.

[Ok here we go]

Would the alt ground strap be a cause as to why my tach bounces around wildly then dies? When I was replacing the intake manifold seals, I cleaned the contact ground patch and tightened the nut. I replaced the capacitors in the tach about 2 months ago and had it tested. The VR is also relatively new - I replaced it 2 years ago with a Valeo part. The alternator was serviced about 5 years ago by Romaine Electric in WA. The battery and the trans ground straps were also replaced a year ago. I have a plug-in voltage meter that goes into the cigarette lighter, and it reads between 12.5 - 14.4, even when the tach bounces and dies. The model year is a 1987. Thanks for any input

[brighton911]

That behavior is similar to how my tach went bad. And the repair was courtesy of Bob Ashlock and his wonder tach board. Tach repair - a new easy way

[manbridge 74]

Learned a good tip way back: use grounding washers instead of flat washers. A grounding washer looks like a anti-vibration washer but the teeth are more substantial. They allow for around 20 points of contact instead of one, the ground paths being increased. Sourced from GM is where I got them.

[Gretz]

I agree on replacement of the ground straps. The process for replacing the straps is generally easier than cleaning up the rest of the ground points throughout the car. The worst ones for me were behind the master cylinder in the trunk and behind the fuel accumulator in the engine compartment. Cleaning all of them and replacing my fuse panel with a modern one were keys in fixing various electrical gremlins.

[Danimal16]

This is a very timely thread. Just finished Targa California and a couple of days of robust driving. When I pulled up my home, I shut the car off; but it would not start again. Opened the bonnet to find that the battery strap had failed and the negative ground braid gave up the ghost and was completely sheared through. LUCKY!

Replaced the battery strap and the ground strap (the original was the one that had sheared).

SOOOO, my clock which had not kept consistent time for the 23 years I have owned this 1971 T is now keeping perfect time.

Check those grounds!

[Jonny H]

The flat ground straps fitted to 911s have a habit of looking 'ok' but they can be oxidised and degraded. This is not fixed by cleaning them - buy new - they are not that expensive.

Cleaning ground points on the chassis and replacing the straps can sometimes get you another whole volt at the battery which can be the difference between charging and not charging.

Another test to do is the battery + cable and connections. Get two long wires for your meter. Connect one on the + at the starter and the other on the + at the battery (yes, both on the +).

You are now measuring the volt drop across the + cable and its connection points. Start the car and switch on every high power accessory you have, even beep the horn. You should have less than half a volt drop. Anything more then clean and remake cable ends and battery terminal connections.

[Hotshot]

Originally Posted by Jonny H

The flat ground straps fitted to 911s have a habit of looking 'ok' but they can be oxidised and degraded. This is not fixed by cleaning them - buy new - they are not that expensive.

Cleaning ground points on the chassis and replacing the straps can sometimes get you another whole volt at the battery which can be the difference between charging and not charging.

Another test to do is the battery + cable and connections. Get two long wires for your meter. Connect one on the + at the starter and the other on the + at the battery (yes, both on the +).

You are now measuring the volt drop across the + cable and its connection points. Start the car and switch on every high power accessory you have, even beep the horn. You should have less than half a volt drop. Anything more then clean and remake cable ends and battery terminal connections.

Amen!

I saw one of your alterbpnators had the big 1AWG and I went and did the same.

My old wires were terrible when metered and checked!

[Hotshot]

Here’s a look at the old strap for the battery. Even though it looks shiny, twisting it revealed oxidized and gross. Replace replace replace!

I used the same AWG on the Alt and used washers to make a great contact.

You can see the front main Ground point.






I also can’t not stress the Ceramicfuses vs the cheap plastic ones. Make sure all these points are shiny.

[GH85Carrera]

Originally Posted by Hotshot

Here’s a look at the old strap for the battery. Even though it looks shiny, twisting it revealed oxidized and gross. Replace replace replace!

I used the same AWG on the Alt and used washers to make a great contact.

You can see the front main Ground point.






I also can’t not stress the Ceramicfuses vs the cheap plastic ones. Make sure all these points are shiny.

I found a set of ceramic fuses from Amazon. I am set for several lifetimes with fuses. The plastic ones are just garbage, and useful to get back home, but not long term. Since my new set of fuse was so many, I replaced all the fuses with new.

[GH85Carrera]

One of the other things that makes me feel much better, is a modified tachometer. The stupid shift light is gone, and replaced with a voltmeter that looks like what the factory should have done. I can see at a glance that the battery is charging properly in all conditions. Even more important, if it dropped to not charging, I know to go check the fan belt and make sure I have the cooling fanbelt running.

[Ok here we go]

Originally Posted by brighton911

That behavior is similar to how my tach went bad. And the repair was courtesy of Bob Ashlock and his wonder tach board. Tach repair - a new easy way

Thanks for the link. I'm going to try replacing the alt ground wire first. Replacing the circuit board on the tach will be my last ditch effort

[Danimal16]

Originally Posted by Jonny H

The flat ground straps fitted to 911s have a habit of looking 'ok' but they can be oxidised and degraded. This is not fixed by cleaning them - buy new - they are not that expensive.

Cleaning ground points on the chassis and replacing the straps can sometimes get you another whole volt at the battery which can be the difference between charging and not charging.

Another test to do is the battery + cable and connections. Get two long wires for your meter. Connect one on the + at the starter and the other on the + at the battery (yes, both on the +).

You are now measuring the volt drop across the + cable and its connection points. Start the car and switch on every high power accessory you have, even beep the horn. You should have less than half a volt drop. Anything more then clean and remake cable ends and battery terminal connections.

Yes, I replaced the transmission strap when we rebuilt the transmission about two years ago.