Electrical Problems

Do the external turn signal lights wok with the ignition on?



Diagrams courtesy of Tmoss & Stang&2birds

Fuse box layout


Mustang 5.0 Lights and Radio schematic, by TMoss:



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.

94-95 Mustang wiring diagrams
Mustang FAQ - Wiring & Engine Info

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

Mustang 5.0 Lights and Radio schematic, by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxLights-Radio_diag.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

Did they work before and just stopped working?

If so, was there any thing that happened between them working and not working?


I recently bought a 89 rolling chassis and they installed a trailer hookup to tie into the rear light and turn signals and ended up melting the harness that runs down the driver side of the car from the fuse panel to all the rear electricals.

Time to break out the test light and DVM and start tracing wires. Did these items work before the prior owner replaced the dash cluster? WHy did he do so? You will most likely need to pull the dash and gauge cluster. Why did the hazard relay burn up?

Foxstang31 said:

Yeah I don't have any of that I'll probably bring it to a shop to get it worked on. He replaced the cluster because he wanted a white one and he added blue LEDs in the cluster and the hazard relay is cracked and was sitting in the glove box when I bought it. Previous owner had an extra steering column to put in and he said that would fix those problems but I don't see how? I tried it and nothing. So how much do you think a shop would charge me for all of this?

Click to expand...

Most shops charge about $80 a hour, maybe more for electrical problems.
Electrical problems like you are describing are probably going to take 2-5 hours. + parts.
For that price, get some electrical education and Do It Yourself.. Of course if you are made of money, have someone else fix it...


Automotive circuits are mostly simple stuff: a power source, a connection path, a control device, a load, and a ground.
The battery/alternator is the positive power source.
The wire and fuses are the connection path.
Control devices are switches, relays and sensors.
A load is a light, motor, solenoid, relay coil or heater element.
In automotive circuits, grounds are the return path so the electrical power can flow from the load to the negative side of the power source.
Electricity flows like water:
Voltage is like pressure,
Current in amps is like volume,
Resistance is like the kink you put in a garden hose to decrease the pressure or volume.
Power is pressure multiplied by volume or voltage multiplied by current (amps)

Digest that, and you just got the first 3 days of Electricity 101.

Use some jumper wires (connection path and ground) to hook up a switch (control device), a battery (power source), a light bulb (load). Now make the light turn on and off with the switch.

That's the electrical lab for the first week of Electricity 101. People pay hundreds of dollars and sit in hard chairs in a stuffy classroom to learn what I just told you for free. So smile, you just got an expensive lesson for free

For free automotive electrical training, see Automotive Training and Resource Site . I have personally reviewed the material and it is very good. If you are new to automotive electrical troubleshooting, I highly recommend you spend a hour or so going through the material. You'll save at least that much time troubleshooting problems.


Using a Multimeter to measure resistance
Almost every meter has a different method for showing an open circuit. An open circuit is one with a break in it somewhere. That break can be a switch turned off, a fuse blown, a lamp burned out, a bad connector, a damaged circuit board or a cut or burned wire.

Without reading the instruction manual that came with your meter, I would not try to guess what your readings mean.

Step 1.) Find the instruction book that came with your Multimeter. Read it and familiarize yourself with how it works and how use it. If you lost the book or didn’t get one with it, do a Google search on the web to find the manufacturer’s web site & download a copy of the manual. Remember that while some meters auto-range to find the correct voltage range, the Ohms function ranges are usually set by the selector switch. Most of the resistance testing done in automotive troubleshooting uses the lowest Ohms range possible.

Step 2. ) Make sure that you know what test lead plugs into which jacks on the Multimeter. There are usually several different jacks on most Multimeters, and they have different functions. Make sure that your battery(s) in the Multimeter are good: if you have any doubts, replace the battery(s).

Step 3.) Once you are sure that the Multimeter is functional and you have the leads plugged into the jacks for Ohms ( the Ω symbol), do some simple measurements to make sure that you know how to use it correctly. Set the switch to the lowest range and touch the leads together: you should not see “nothing” but you should see 0.3-1.0 ohms. Measure a 60 watt light bulb: cold it will measure about 17.5 Ohms. It you measure it while it is hot, the reading will be greater.

Step 4.) Make several test measurements using the ohms function and the DC volts function. Remember all resistance measurements must be done with the power off the circuit. This avoids false readings and possible damage to the ohmmeter.. Repeat steps 3 & 4 until you are sure that you can do it without making any mistakes.

Step 5.) Then see and carefully study ALL the information under the Heading Chassis Electrical, Basic Electricity – Understanding & Troubleshooting

Step 6.) Go back and carefully re-read both of my previous posts and download and print the diagrams from the link posted. http://www.autozone.com/servlet/UiB...23d801ddb3c.jsp for wiring diagrams.

Step 7.) Apply what you have learned and make the test measurements using the information in the wiring diagrams & my previous posts.

Foxstang31 said:

Yeah I don't have any of that I'll probably bring it to a shop to get it worked on. He replaced the cluster because he wanted a white one and he added blue LEDs in the cluster and the hazard relay is cracked and was sitting in the glove box when I bought it. Previous owner had an extra steering column to put in and he said that would fix those problems but I don't see how? I tried it and nothing. So how much do you think a shop would charge me for all of this?

Click to expand...

Suggestion- get yourself a Chilton and a set of good tools and basic diagnostic equipment if you plan on keeping the car. It is a 20+ year old car that has known issues. Unless you start to tackles some problems yourself, it will turn into a money pit. He may have been referring to the ignition swtich and wiring that are located on the column.

As far as cost, take shop labor time and multiply it by the # of hours it will take to fix. Electrical problems are the worst to chase down. Could be $50. Could be $500..

mikestang63 said:

Suggestion- get yourself a Chilton and a set of good tools and basic diagnostic equipment if you plan on keeping the car. It is a 20+ year old car that has known issues. Unless you start to tackles some problems yourself, it will turn into a money pit. He may have been referring to the ignition swtich and wiring that are located on the column.

As far as cost, take shop labor time and multiply it by the # of hours it will take to fix. Electrical problems are the worst to chase down. Could be $50. Could be $500..

Click to expand...

This is some of the best advice you can get. Take and go with it. Fox body Mustangs are a leaning experience. You either lean how to fix it or you lean that you can't afford it.

Foxstang31 said:

Thanks for all the info guys since I'm 18 and have no bills all my money will go into this car till it's absolutely perfect. I called a shop and I'm going to bring it up there this week and they are going to look at ill keep you guys updated

Click to expand...

I suggest you read the following posts by other members who also spend money to get the perfect car.

• " want to blow 4 years and 40K on a Foxbody?" - Scott probably now has 5 years and $60k in his car
  
• "my never ending 89 Notch Thread" Jeff probably has over $30k in his car

Come back and tell us what the problem was with this issue and the cost to resolve it.

The horn circuit has a button that supplies ground, a relay that uses the button to switch the horns on and off, and two horns. The relay reduces the current that the horn button has to carry. This makes it possible to use a small and simple switch and slip ring on the steering wheel.

Note that the horn ground is built into the horn mount bracket, so the horn must be mounted on metal with a good connection to the car body.






The horns typically develop an internal short to ground, which causes the fuses to blow.

The horns are located under the car on the driver's side, forward of the front wheel well. Disconnect BOTH horns, replace the fuse: if the fuse blows immediately, the problem is most likely in the cigar lighter circuit. If not, then press the horn button on the steering wheel: if the fuse blows the problem is in the wiring between the horn relay and the horn. If doesn't blow when you press the horn button, connect ONE of the horns and try again. If it still doesn't blow the fuse, connect the other horn. Chances are that the first horn you re-connect will blow the fuse. Whatever horn blows the fuse at this point has an internal short and is trash. Time for a trip to the junkyard...

Horn does not honk, but does not blow fuses:
Run a jumper wire from the battery positive terminal to the horn input connector: the horn should honk. If it does, then your problems are in the other parts of the circuit. If it does not honk, replace the horn.
Use a test light or voltmeter and connect one lead to the horn wire under the fender and the other to ground. Push the horn button: you should see 12 volts or the test light will turn on. If it does not, check the fuse. If the fuse is good, check the relay.

The relay will click and honk the horn if you short the Yellow/Lt Green wire to ground. If you have a test light connected in place of the horn it will light. If it does not activate the horn or test light, look for 12 volts at the Lt blue/white wire. No 12 volts at the Lt blue/white wire, you have fuse or wiring problems in the circuit that supplies the 12 volts to the relay. Good 12 volts at the Lt blue/white wire and the Yellow/Lt Green wire shorted to ground and no honk or flash of the test light, replace the relay.

The rubber foam usually deteriorates over time and that is what makes the horn switch fail. Take it apart and replace the foam with some from packaging material. A little creative engineering may be required, but you can do it.