No Power

[2MustangGTS]

My 89 GT Convertible has been running fine. Yesterday I got in turned the key and ... absolutely nothing. I checked the battery, which is new, new positive wire, new solenoid and even a new alternator. OK, battery was low so put a charger on it. Charged up quick and still no power. Took Positive cable off and the battery showed power, charged it and it came up fine, put cable back on and ... immediately it dropped. OK, took cable off, charged it again, put the cable on and quickly hit a door lock (electric) it moved slightly and .. battery nearly dead. OK, the key was not on or even in. Nothing works. It seems there is a dead short, a major one. One possibility is the convertible top motor which the other day struggled to get the top down and up. Is there somewhere I can take it out of the circuit. The connections behind the seat do not want to come apart and are very hard to access, is there another point I can take it out of the circuit? Is it possible it is drawing power and killing the electronics or ....... where else can I look?

 

[TuneUpsNSuch]

Have battery properly charged/load tested, may be defective.

 

[89oem]

Battery can have full charge (Volts) but no Amps. No Amps = symptoms you describe.

 

[jrichker]

Diagrams courtesy of Tmoss & Stang&2birds

Convertible top wiring diagram

Fuse box layout

Troubleshooting battery drains
Typically it is something draining the battery. Small things like glove box or courtesy lights are often the culprits. If you have an aftermarket stereo or alarm system, it is also suspect.

The ideal method is to disconnect the negative terminal, and connect a Digital Multimeter (DVM) between the negative terminal on the battery and the negative cable. Set the DVM on a low current scale of 2-5 amps if it doesn't auto range. Watch the current draw, and then start pulling out fuses. When you see a sudden drop in the current, that circuit is the likely culprit. Note that the computer, radio & clock will draw less than 1/10 amp to keep the settings alive.

See http://assets.fluke.com/appnotes/automotive/beatbook.pdf. You will need the Adobe Acrobat viewer which is also a free download – Adobe Acrobat Reader DC Install for all versions

If you can’t find the current drain by pulling fuses, then the alternator is suspect or any aftermarket sound or lighting equipment that may be on the car. Disconnect the alternator output power plug, then disconnect any aftermarket sound or lighting equipment while watching the current on the DVM.



See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info Everyone should bookmark this site.

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

T5 Cutaway showing T5 internal parts
http://www.veryuseful.com/mustang/tech/engine/images/5_Speed_Cutaway_Illustrated.jpg

Visual comparison of the Ford Fuel Injectors, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/Ford_Injector_Guide.jpg

 

[2MustangGTS]

Thanks to everyone. The battery was 7 months old so I did not think it was the problem. Pulled it and used one from another car and everything was fine. Went to the parts store where I bought the bad one and was given a new battery.

Thanks again.