Electrical Turn Signals, Very Strange Problem

Discussion in 'Fox 5.0 Mustang Tech' started by 89withatrunk, Oct 18, 2013.


  1. 89withatrunk

    89withatrunk New Member

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    89 mustang lx 5.0

    I know this topic is often covered, but this is quite different than from the problems that I've been reading for the past 2 hours. My turn signals went out once before for some odd reason, I fixed them, dont remember how, I think I put in a new connection for hazard switch,a new flasher. had the dashboard , gauge cluster, etc. all out , reinstalled it. now here I am a year later turn signals not working again, but it's strange. When I turn hazard switch on, I hear flasher working, I can see all 4 lamps blinking on exterior of car, but only one green arrow blinks on gauge cluster. When I hit turn signal switch, NOTHING. I swapped flashers, nothing changed. messed around with switch on column, no results. I even replaced ignition switch.
    what next? I don't have great knowledge with electrical system diagnosing, wouldnt know how to test the multifunction witch or any other switch... about to take this POS to the shop and have a mustang master go through everything electrical, including codes 12 and 41,, engine loses power while driving. I've been working on this car for years, new engine, a lot of parts new, still cant get it finished and I'm so close. I hate giving up , but I've had enough of this never ending problem. just need car in good running condition to get to a shop to get a smog, (yes, California is the best) and then maybe, just maybe, this car can really see the road again. PLEASE HELP!
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  2. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Are you having problems with other electrical items like the radio, wipers, heater blower?

    The codes are a somewhat simpler problem.
    Code 12 is an idle problem and the best resources as follows:
    You guys with idle problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix you idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix. :D:

    Code 41 or 91 Three digit code 172 or 176 - O2 sensor indicates system lean. Look for a vacuum leak or failing O2 sensor.

    Revised 06-Sep-2012 remove smog pump crossover tube reference

    Code 41 is a RH side sensor,
    Code 91 is the LH side sensor.

    Code 172 is the RH side sensor
    Code 176 is the LH side sensor

    The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

    The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
    "When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

    When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

    Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

    Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

    Testing the O2 sensors 87-93 5.0 Mustangs
    Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear.

    Disconnect the O2 sensor from the harness and use the body side O2 sensor harness as the starting point for testing. Do not measure the resistance of the O2 sensor , you may damage it. Resistance measurements for the O2 sensor harness are made with one meter lead on the O2 sensor harness and the other meter lead on the computer wire or pin for the O2 sensor.

    Backside view of the computer wiring connector:
    [​IMG]

    87-90 5.0 Mustangs:
    Computer pin 43 Dark blue/Lt green – LH O2 sensor
    Computer pin 29 Dark Green/Pink – RH O2 sensor
    The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.

    91-93 5.0 Mustangs:
    Computer pin 43 Red/Black – LH O2 sensor
    Computer pin 29 Gray/Lt blue – RH O2 sensor
    The computer pins are 29 (LH O2 with a Gray/Lt blue wire) and 43 (RH O2 with a Red/Black wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


    Testing the O2 sensors 94-95 5.0 Mustangs
    Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a red/black wire) and 27 (RH O2 with a gray/lt blue wire). Use pin 32 (gray/red wire) to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


    Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

    Testing the O2 sensor wiring harness
    Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer. Using the Low Ohms range (usually 200 Ohms) you should see less than 1.5 Ohms.

    87-90 5.0 Mustangs:
    Computer pin 43 Dark blue/Lt green – LH O2 sensor
    Computer pin 29 Dark Green/Pink – RH O2 sensor
    Disconnect the connector from the O2 sensor and measure the resistance:
    From the Dark blue/Lt green wire in the LH O2 sensor harness and the Dark blue/Lt green wire on the computer pin 43
    From the Dark Green/Pink wire on the RH Os sensor harness and the Dark Green/Pink wire on the computer pin 43

    91-93 5.0 Mustangs:
    Computer pin 43 Red/Black – LH O2 sensor
    Computer pin 29 Gray/Lt blue – RH O2 sensor
    Disconnect the connector from the O2 sensor and measure the resistance:
    From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 43
    From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 29

    94-95 5.0 Mustangs:
    Computer pin 29 Red/Black – LH O2 sensor
    Computer pin 27 Gray/Lt blue – RH O2 sensor
    From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 29
    From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 27

    There is a connector between the body harness and the O2 sensor harness. Make sure the connectors are mated together, the contacts and wiring are not damaged and the contacts are clean and not coated with oil.

    The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

    Make sure you have the proper 3 wire O2 sensors. Only the 4 cylinder cars used a 4 wire sensor, which is not compatible with the V8 wiring harness.

    Replace the O2 sensors in pairs if replacement is indicated. If one is weak or bad, the other one probably isn't far behind.

    If you get only code 41 and have changed the sensor, look for vacuum leaks. This is especially true if you are having idle problems. The small plastic tubing is very brittle after many years of the heating it receives. Replace the tubing and check the PVC and the hoses connected to it.
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  3. 89withatrunk

    89withatrunk New Member

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    thanks jrichker..

    O2 sensors are brand new. do you happen to have a detailed vacuum diagram for the 89 5.0? and fyi, smog pump and everything associated with it are deleted. also, I replaced 55mm TB with 70 from 93 cobra, and used my existing MAF sensor.. not getting trouble code for sensor, but when engine is running and I unplug MAF, nothing happens. I thought engine is suppose to cut off in effect.
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  4. 89withatrunk

    89withatrunk New Member

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  5. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Swapping the MAF sensors between different MAFs is a big no no. The MAF body and sensor are designed to match each other. Therefore you can't swap sensors between different part number MAF bodies and maintain proper calibration. The assembly is designed to match the computer’s internal program, and swapping a different MAF can upset the computer's calibration.


    The OEM Ford MAFs are not calibrated to injector size. The injector sizing is done in the computer’s internal programming. Aftermarket MAF’s “lie” to the computer in an attempt to fool the computer into changing the injector pulse on timing to match the increased airflow.

    The only other MAF that is a one for one swap for a 93 and earlier 5.0 Mustang is the 94-95 Mustang MAF.

    94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes. *1 *2

    Once your replacement 70MM MAF is in place, disconnect the battery for about 10 minutes. When you reconnect the battery and start the engine, the computer will relearn the settings for the new MAF.

    *1.) Metal flange adapter http://www.kustomz.com/cat3.html Buy the TR70 for $44.95. Or spend some time on eBay looking for one that may fit.

    *2.) MAF & sensor interchange
    The 94-95 Mustang 5.0 MAF & sensor is also found on:
    1995-94 Mustang 3.8L F2VF-12B579-A2A,
    1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
    1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
    1994-92 Town Car 4.6L F2VF-12B579-A2A,
    1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
    Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.


    PM me your email address and I will send you a complete Ford Factory 89 Mustang electrical diagram set. The zip file is 2.5 MB and is too big to fit through Stangnet's email gateway.
    89 Mustang wiring diagrams zip package–

    They are in a zip file format to reduce the size of the package. If you don't have Windows 7 or Windows 8, you’ll need WinZip or other Windows archive tool to extract them from the zip file.. See www.majorgeeks.com - Download Freeware and Shareware Computer Utilities for a free download.
    The diagrams show the location area and the connectors are drawn to the same shape as those in the car.
    You will need the Adobe Acrobat viewer which is also a free download – www.adobe.com/products/acrobat/readstep2.html - Adobe Reader download - All versions
    #5
  6. cobra10494

    cobra10494 Founding Member

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    In reply to your signal issue it sounds like your multifunction switch.
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