Pretty sure my Convertible has grounding issues. This would explain a few weird things. First, the radio has "noise" and the some instrument cluster gauges move with the turn signal. Second, my stock 89 Auto LB9 ECM has had a strange problem that seemed to come out of nowhere after I did an extensive tune up on the engine that went all the way to the valve stem seals and timing chain. I may have disturbed or broken some grounding in the process now that I think about it.

Being a convertible, I have noticed that when I open the dash or look under the console, that a light brown "rust" is present after so many years. I am pretty sure this was a beach area car for many years so I would not be surprised if various ground areas are weak or bad from corrosion.

I am planning to check chassis and body grounds, equipment grounds (like the instrument cluster), and ECM grounds.

My plan is to start with a jumper from the battery (-) to various points on the engine block and body panels.

I have read in other posts that anything above .02 ohms needs work.

I also have read that there are several ECM ground circuits that should be checked as well. I have found which pins these are in other threads and will check those.

Any advice or things I have missed? I am hopeful that cleaning up the grounds will solve the remaining audio and ECM issues on this car.

 

There really aren't that many grounds on the car, so it shouldn't take too long.
The dash is one that I have thought about. I think the ground is to the dash carrier, which is then screwed to the firewall, the connection there could be slightly resistive, or opening. I would ran another terminal from there to you'r own connection to the body to tie everything together

 

 

thanks all. I will report back with my findings...

 

As Scooter hinted at, our cars are woefully under-grounded. In addition to checking your grounding wires and straps I would also add grounding wires. From your battery I would have three grounding wires, a 10 gauge that grounds to the Core support for the headlights, at least a 6 gauge to one of the frame rails and another ground that goes to the engine block. The ground to the engine block should be the same gauge as the power wire to the starter. One of the heads should be grounded to the firewall with at least a 6 gauge and both heads should be grounded together. The transmission is also relatively easy to ground to one of the inner frame rails. All cars also have the grounding points painted so you need to either buy some star washers and torque them tight so the teeth bite into the metal or use one of the round wire brushes for a drill to clean the paint and rust from the grounding location. Use Anti Seize on the screws and mating surfaces and not dielectric grease.

 

Not to argue, but this seems a bit excessive. Would you be able to explain this one? Just wondering what the thought pattern is for that?

Also, I would add one to your list. I have read from an alternator place that also suggested running a ground wire from the alternator case to the engine block as sometimes electrical gremlins can be chased and it can stem from a bad case ground connection to the alternator.

 

The answer to your question is almost in the second part of your reply. Most likely if they had appropriate grounding of the heads they wouldn't need an additional ground. The alternator and ignition systems make enough noise that the factory grounding system really isn't sufficient. As far as the heads go, I think the factory only grounds one head to the firewall and the engine block to the frame or battery. The heads are separated from the engine block via the head gasket and the heads from the intake via the intake gasket. The only thing linking them together are the head and intake bolts that should be coated with teflon tape, thread sealer or something else, neither of which promote conductivity. You're only options are to either ground one head to the body and ground the heads together or to ground each head to the body. I've also heard of guys that have iron blocks with aluminum water pumps to also ground the water pump to help decrease the rate of galvanic corrosion

 

Awesome feedback. I did run extra grounds with #12 THHN stranded to the heads, intake manifold, block, and O2 sensor housing. They all run to body locations. I also ran a big one from the battery to the passenger fender. This alone cured a random idle drop-dead. I'm sure there are many places with weak grounds on my particular car. I will certainly add the headlight center.

 

I find it hard to believe that the 15 bolts per head, and some aren't coated, aren't enough contact points to the block. I'm not saying you're wrong, I just think it is unlikely. Food for thought, for sure.The problem with the alternator is that you have an aluminum case, which is unprotected and is vulnerable to oxidation from the air and salt. I think there is more likelihood that the alt ground would be more an issue than heads. Either way, it's not a bad idea.

There is one thing that you haven't mentioned, ground loops. If you're going to add a bunch of grounds, you can introduce ground loops. This is why GM grounds most of, if not all, the engine stuff to one place and keeps the amount of grounds to a minimum. I wouldn't go too crazy with adding too many to the body, I think wire size and good contact area is more important than the quantity and location. I like to use the star washers like you mentioned.

 

Just having continuity isn't the whole picture. Forgot to mention that MSD also recommends grounding each cylinder head. The weaker your ground path is the weaker your spark is. The materials in the head, bolts and block are also different so you can get galling and electrolysis which will weaken the electrical connection of the bolt. One way to avoid ground loops is to ground as much as possible to a single point.