Topic: 87 Mustang - battery keeps dying

[06JettaTDI]

I have an 87 Mustang with a 5L 4-bbl.  The battery and alternator are new.  If the car is left more than a week, the battery discharges and won't start.  Any suggestions

[Arthur Dent]

I'd guess you have a wiring that is grounding its self.

[initial_D]

Do you have an aftermarket stereo, alarm, remote starter system installed?

[articsteve]

My first look would be to the ignition switch and that your juice is running out of the starter when off and the key is out.

One good thing about Ford of that era is they kept the starter solenoid off the starter and in the engine bay.  You could try disconnecting the hot wire to the solenoid when not in use or put a digital meter on it.

Go to a Mustang forum. 

[06JettaTDI]

Do you have an aftermarket stereo, alarm, remote starter system installed?

yes, I have all that and detach the face-plate when the car is parked.  when I had the alternator replaced a few weeks ago, they checked the draw from that source and it was miniscule.

[articsteve]

Check the super obvious.  Glove box and trunk lid.

[06JettaTDI]

Check the super obvious.  Glove box and trunk lid.

Done and done-er.  Taking it back to the shop where I'm sure they'll replace yet another component in the electrical system and cross their fingers.  I have to admit, after the new alternator was installed, the old beast was easier to start - except after it had been sitting too long

If the car hadn't belonged to my late mother...

Thanks for all the feedback!

[initial_D]

How did those 'shop guys' measure the total current draw?

You can stick an AMP meter on the positive terminal of the battery to measure the 'leakage' when the car is OFF, and turn the meter to DC Volt and measure each device that has a power connection ... the most difficult thing is to get to them ... when buried inside the dash ...

[articsteve]

How did those 'shop guys' measure the total current draw?

You can stick an AMP meter on the positive terminal of the battery to measure the 'leakage' when the car is OFF, and turn the meter to DC Volt and measure each device that has a power connection ... the most difficult thing is to get to them ... when buried inside the dash ...

How did those 'shop guys' measure the total current draw?

How did those 'shop guys" conclude the starter and alternator needed replacement? 

[mar1990]

How did those 'shop guys' measure the total current draw?

You can stick an AMP meter on the positive terminal of the battery to measure the 'leakage' when the car is OFF, and turn the meter to DC Volt and measure each device that has a power connection ... the most difficult thing is to get to them ... when buried inside the dash ...

To narrow down which circuit pull a fuse and stick the leads of the AMMETER on the two fuse connections to see what each branch is drawing. Do this one by one on each fuse, both under the dash and in the engine compartment.

[06JettaTDI]

The fellows at Fountain Tire informed me that the old (Motomaster) battery is hooped i.e. will not hold a charge.  So, I decided to have them put in a different one, and I took the "old" one back to Canadian Tire.  The idea was to get a replacement battery to keep as a spare.  CT charge the old battery and told me there's nothing wrong with it.

It will be interesting to see what happens now.  Depending on who I believe, either my electrical system is not causing the battery to die or I bought a new battery I didn't need.

[barrie1]

How many CCA's is this particular Battery you are having problems with as the Canadian Tire Batteries are not all really that good a product  for very long at all. 

[06JettaTDI]

How many CCA's is this particular Battery you are having problems with as the Canadian Tire Batteries are not all really that good a product  for very long at all. 

Not sure about the Amps.  CT only had one battery that would fit my car.  With the 4-bbl instead of FI, it's a bit of chore to crank it over - although, the new alternator helps.  Time will tell.

[barrie1]

As a suggestion I would check the contact points on the inner fender well where the Solinoid and the brain box bolts onto. The legs on the bottom of these 2 devices have to have a nice clean surface on them as they actually ground with the part. Make sure theres No Rust under each foot part of them as it will create a short and can kill the Battery over a short period of time.