Electrical Gremlins?

[MattyFD]

Hey,

My 90 SHO is having major problems. It dies whenever it sits for over 10 hours. The shop put in a new battery (they said the old one was the problem) and tightened the battery connections. They kept it over night (more than 10 hours) and it started up fine when I went to pick it up yesterday. I drove it about 20 miles yesterday and all the electronics in the car seemed fine. I opened the sunroof, listened to the radio, etc. Then I go to start it up this morning, and its dead again, just like before. Its back at the shop now. They are stumped... they have no clue what could be wrong because now the battery is brand new and the alternator was just replaced a few months ago and checks out ok too. Any thoughts as to what this could be?
Thanks.

Matt FD

 

[MattyFD]

no ideas?

matt fd

 

[MattyFD]

Update, the shop says its an alternator cuz when it idles, the alt reads a strong 15, but when they turn on all electronics, it reads around an 11. This sound plausible?

Matt FD

 

[DougLee25]

Yes, that is a possibility. Also, you may have a slight draw of power when the car is off. I had an amp before do this. Take your positive battery cable off and hook an amp meter in line with the battery and the power wire. If the meter reads a current draw with all acessories off, you have a constant drain on the battery when the car is off. This is what is causing the battery to die. Make sure all under hood lights are off as well, as this will put a draw on the meter. So if the meter does read something, then start pulling fuses until you find the suspecting circuit in question. When you do find it, the meter will not show a current draw. Let me know if this helps.

Doug

 

[naval-avi8or]

You definetly need to check the draw with everything off. I had a new radio installed in an old car of mine and the internal memory batt had went bad ie. shorted and was pulling a constant draw that was draining my batt. BTW when I say draw that's amps not volatge drop. So if you do not have a amp clamp you will have to take it and have it done at a shop or spend the around 100 ducks for a multimeter/amp clamp. I got one at sears works great. I would also have the alt tested off the car if you didn't the first time. If they just took a voltage reading at the bat to test the charging system it is not sufficent. As soon as you load the alt up with accessories the voltage drop is normal at least it is on my brand new alt.

 

[91MochaSHO]

We had a 1988 Taurus, I know the dash boards are different, this might apply for a 89. I know that there are sometimes problems with the glove box light staying on. This caused the battery to run dead after it has sat for awhile. You might check something like that. Possibly the mercury switch in either the trunk or the hood is sticking. Maybe a faulty ignition switch is causing a draw. Make sure the Cold Cranking Amps is right for the SHO, the SHO requires more. My SHO had too weak of a battery. It was new when i got it but i had to buy a more robust Diehard Silver cause the other one kept on dying cause they must have overlooked the SHO specification for a higher CCA over a Non-SHO.

 

[pjtoledo]

Great picture!!!

Perry Toledo,Ohio