I'm assuming it's an Oldsmobile. Can you say the year, model, etc. It may help.

 

What kind of car is it? There's usually a ground wire going from NEG at the battery to the case of the alternator.

Pics and more info would definitely help.

 

my chevelle has one and it goes to a little junction block behind the battery,it's got 3 or 4 wires and they ground to the radiator support,and if it's not there it will not crank.

 

Whatever that wire is, its not going to prevent your car from starting. Do the headlights come on bright? Do they dim when you try to start the car?

 

Both my '68 and '69 4-4-2 convertibles have the little wire going from the negative battery cable to the core support, just adjacent to the battery.

Randy C.

 

Sorry about that. I have a 72 cutlass convertible. See the attached pic. Also, I think the battery is dead as no lights come on...not even when you open the door.

I wonder what that goes to. The frame?

 

A dead battery will definitely prevent the car to start. And again, that wire will not prevent the car from starting unless the big black battery cable is no good. Chances are if that's the case the little black wire will melt.

 

As a matter of fact, my battery tender doesn't like this battery. I think the voltage is way to low for it even to crank. I took a multimeter to it and I believe it was reading in the 4s or 5s. Even if the problem is the battery, I'd still want to know where that wire goes. I cannot find the other end or terminal where it attached.

 

It should be shown in the CSM or the AM.

 

It should ground to the core support alongside the battery

 

Thanks. I'll look into this when I get home.

 

What Randy said. Invest in the manuals for this car they are worth it. You should see a hole on the drivers side of the radiator core support which this wire attaches to. Clean the terminal and the spot on the core support before using a sheet metal style taper threaded bolt and star style lock washer. Careful to not puncture the radiator tank with the bolt. The bolt is very shallow. I like to spray battery terminal protectant on the cleaned connection. This keeps it in tact longer.

Pull the battery and have it load tested. Id do the same for the alternator. Have it bench tested. That battery looks like the wrong "group" size for the car, Replace it with the correct "group" size and CCAs...at least 650-750 CCAs IMO...

Clean both sides of both the positive and negative cables. The negative battery cable should be attached to the engine behind the power steering pump with a shallow bolt and a star washer. There is a ground strap that connects the rear of the cylinder head to the firewall. Install one if its missing or ratty.
With a fresh battery and good cables and connections the car should start right up as long as the starter and solenoid are in good shape too.

Fusick, Year One and others offer OEM parts for your car. Dont go the big box places and try to find "will fit" grade zero parts & fasteners.

https://www.fusickautomotiveproducts.com/
https://www.yearone.com/Catalog/1964.72.cutlass.442

 

That is an accessory ground there to get the front end of the machine in electrical balance a little more quickly than bouncing back through the block and alt case. Prevented flickering headlights. Will absolutely not prevent car from starting if not hooked up.

 

If you know the battery is dead, thats your problem. Get a good battery and go from there

 

 

Good news, but dont rest yet...A new battery will mask bad or not so good grounds and other tired components. In other words, the charging and starting system are still working harder than designed. Which will tax the new parts (battery in your case) and reduce life expectancy on the rest. Every 40-50+-year-old vehicle should have its grounds and + connections cleaned and sealed. ? Read your charging VDC. It should be 13.8 to 14.2 VCD ish. The voltage drop should not dip below 10.5-11.5 VDC...ish.

 

Ok so from the battery, you connect the 2 wires from the negative terminal to the engine block (Thick wire) and to the frame (Thin wire). Does this thin wire allow you to connect other grounds to the frame? Or it has noting

 

The negative big wire I think goes to the alternator housing, someone will confirm.

The little wire goes to the core support (black thing that holds the radiator and headlights. Move the wire around and look for a mysterious hole (or one with that bolt above) in reach of the wire for no good reason. This provides an additional ground path for the core support for the headlights.

Everything else is grounded to the body. There is a large braided ground strap somewhere from frame to engine, and probably one from body to frame. The fisher body manual and chassis service manual will have details. You should get those books for your year.

 

I posted this the other day in another thread the batt neg bolts to the block just below the drivers side head, in the post the other day i incorrectly stated it bolted to the head.

 

The thin 10ga wire attaches, as we described, to the radiator core support. Look at the vertical driver's side metal support that the radiator sits in. The wire is the right length to reach it. At least that's where it attaches in a 68-69. The assembly manual for your car will show the correct location if I'm incorrect.

 

Generally a black wire is on the negative post of the battery and bolts to the engine block. Be sure its metal to metal, remove any paint, grease, grime, etc where you put the ground. The Red goes to the horn relay on the drivers inner fender.
Its ok to put extra grounds. There is usually one on the firewall behind the motor that also bolts to the motor, usually a valve cover bolt or anything (clean) within reach. The heaver the wire the better. I also put one at the rear of the car, frame to body. My extra black off the battery terminal was/is on the drivers inner fender, i added another to the same screw to the radaitor core support. Cant have too many grounds.
Steve

 

this^^^^^^same as 1970