Phil Harrison

This has confounded me for about 3 months.

Car ('88 944Turbo) had battery replaced with an Optima about 2 years ago.

In the last 6 months, I have had to jump start from battery pack all the time, once started voltage has shown 11-12 volts on gauge.

I checked engine rail grounds & battery ground = OK, as the car started well from battery pack I assume the engine grounds are good.

I replaced the alternator yesterday, have driven about 60 miles, but the battery is still flat & the gauge still shows about 12v!

So I got a DVM, with car not running battery terminals have 11.12v across them.

After starting the car from the battery pack I have 12.7 --> 13.16 v across the battery terminals. After 10 minutes the +ve battery cable is hot & the battery terminal is too hot to touch.

Car will not start from it's battery, does anyone know what's wrong here?

Why does the gauge show 1 v low? Any way to fix it?

Any feedback appreciated

dime1622

if it gets hot, your grounds probably arent ok. smaller contact area = smaller effective thickness = less current capacity = more heat. like when you use wire too small for your subwoofer amp - the amp will overheat until it shuts off.

streckfu's

Sounds like it's time for batery cables from Iceshark.

Make sure your ground is OK. It's a real pain to get to the contact at the back of the engine. Make sure the connections are OK at the starter as well.

Mike

1. If your +V connector is hot, then the connection between the cable and the battery is a likely culprit. It can be loose, dirty, corroded or a combination. Anything that reduces the surface area of the connection will raise the resistance, causing it to heat up when current passes through it.

2. Since your no-load terminal voltage is low (11.1V) it's possible your battery is bad. Have you had the battery tested?

Clipboard

Mike - I'm having the same issue with my 83SC but: new battery-to-ground cable and new Optima. Could there be some incompatibility between the battery shut-off and everything else?? I'm electron challenged, if that's not obvious.
BTW: are you a Bone driver? and Where in CNY?, I'm moving the SC to Seneca County next weekend.
john

Charlotte944

Your battery has a shorted cell.

Each cell has a potential of about 2.2 volts. So, 2.2 volts X 6 cells = 13.2 volts. Conversely, 11.2 volts / 5 cells = 2.24 volts

special tool

Yup - shorted cell, or corrosion climbing the positive cable at the battery connector UNDER the insulation (peel it back )

z3bra

Boy that's the truth, I think I had to go back almost two feet from the terminal ends on that set of red wires that go to the fuse box to get to where they weren't corroded. The positive cable to the starter was almost as bad too as well as the insulation being cooked and dryrotting. I ended up just putting the ones that go to the fuse box into one piece of 4 gauge welding cable on the battery end of things with a soldered butt splice to simplify it.

Also take a look at your main positive lead going to the starter from the positive battery terminal. It's probably corroded all to hell and the insulation has probably seen better days too because of the proximity to the downpipe off the turbo. Time for an Iceshark kit or to make your own with welding cable. Alternately you could always pay way too much for another factory piece that'll be good for another 15 years or so if not more since you're using an Optima. Just get some high temp fiberglass sheathing for it to make it last longer near the exhaust and have some additional abrasion resistance.

I'd also like to take a moment to say damn group 40 and 41 leaky POS batteries straight to hell. I hate em.

You're in good shape now using the Optima but the damage was started by the original and subsequent leaky batteries over the years.

Oh yeah, also check the starter to alternator cable while you're in there, it's close to the exhaust too and if you're going to replace the battery to starter piece you'd probably be well advised to replace that one too while you're at it. Cooked insulation on a cable that more or less is laying on top of the engine block could lead to a short which in turn could cause a fire which in turn leads to a very unhappy 951 owner who has an engine on fire.