Instrument Cluster Burned??

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numlaar

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Hey Gang,

OK my lovely Bronco is acting up again... the other day while driving home from the boat ramp, I noticed a burning smell... it smelled more like brakes burning to me, than electrical, but it was in fact something electrical... Something burned, and now my speedometer/odometer no longer work. In addition, because the truck doesn't know how fast its going, the ECM can't tell the E40D transmission when to shift. It was definitely inside the cab for the burning, and definitely coming from the driver's side dash area... 

(OH Also I did notice previously the speedometer would go wonky around 65-70MPH) needle would bounce all over the place... sign it was going bad?

I am just curious if anyone else has experienced anything like this, and where I should start to look to fix it...

I am guessing it was the instrument cluster itself, or the speedometer in the cluster, but I'm not sure. Before I go ripping it all apart, I am looking for advice. If it wasn't the cluster, then I have no clue!

There's a good deal on eBay right now for a cluster for 99.00 bucks, so I am tempted to just go ahead and buy it to have it handy.

Thoughts??

 
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miesk5

96 Bronco 5.0
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yo N,

Could be the EEC IV smoked some capacitors; OR the 4WABS Module or PSOM Module took a dump.

EEC First; remove driver's plastic kick Panel and look for smoked aroma or a water leak and rust.

EEC Capacitor Failures Due to Age by Joel B

http://sbftech.com/index.php/topic,15654.0.html

EEC Removal & Swap; bossind (boss, Steve)

"http://www.supermotors.net/getfile/764609/original/dsc_0034.jpg

The best way to do this is through the drivers side wheel well by loosing off the plastic inner fender as shown

I label all my computers when I remove them so I didn't get them mixed up.

Pulling back the plastic inner fender you will have access to the computer harness, this requires a 10mm socket to remove. Next you remove 2-11mm nuts on ECU rubber gourmet, remove the grommet and pullout the ECU. Here the ECU is already removed

http://www.supermotors.net/getfile/764610/original/dsc_0035.jpg

Slide in the new ECU

http://www.supermotors.net/getfile/764611/original/dsc_0040.jpg

The rubber grommet, notice the marking for "top".

http://www.supermotors.net/getfile/764612/original/dsc_0044.jpg

Reinstall the grommet, nuts and tighten down the harness and the ECU is installed.

http://www.supermotors.net/getfile/764613/original/dsc_0046.jpg

+

"It comes out into the engine compartment, not the cab, so removing all of the kick panel stuff is not necessary. Just drop the fender well housing on the drivers side and reach in above the tire, unbolt the wire harness, unbolt the EEC cap and slide it out. Some say you don't need to drop the fender well, but I'll say from experience that it makes it 100x easier. Steve mentioned the capacitors, which on these old ECU's will pop eventually, but it might not be as noticeable as frying the EEC and emitting that obvious burnt electrical smell and it could be hard to see too. Here is a picture of mine with the bad capacitor, all you can see is a little browning around the component and some white around the base. The good news is that if it is the capacitors then it can usually be repaired. I got mine done for $125+shipping, which included new capacitors which I am told will not ever fail again, but depending on your specific EEC needs you may be able to replace it for a similar cost, only thing is you will likely have more old capacitors in the replacement.

Get a 5.5mm (7/32") 6-point socket (and a #2 phillips if your truck has wheel arch mouldings), and pull rear of the wheelwell forward. Then you'll need 10mm, 11mm, & maybe 8mm to pull the EEC itself.

Capacitor Repair, Failures Due to Age; "...(A9x and same years ECM's) The patient in question is a remanufactured A9L unit. This ECM is the one from a little notch project I'm working on. It started giving some problems starting up, engine flooding, random hesitation, missing and stalls. I opened up the ECM (the car is running with a A9S unit) after the owner brought it for a checkup.What you see is the typical electrolytic capacitors leak, causing intermittent shorts/opens to the neighboring circuits/components and symptoms as the ones explained. Worst case scenarios with this type of failure, is a permanent no start and permanent damage to the PWB preventing it could be repaired. As soon as I replace the capacitors..." by ActualUtilityVehicle

=============

PSOM;

This problem could be caused by a # of things;

bad vehicle speed sensor (VSS) (also called ABS,, DSS sensor) sensor on 8.8 (rear differential)/ or

Connector/corroded wires inside connector;

or cruddy/damaged tone ring in the 8.8.

bad 4WABS Module - It is located below ws wiper fluid/coolant recovery tank. So, the connector can be corroded by leaking fluid

bad wiring/shorts /connectors from VSS at firewall, at 4WABS Module and /or at PSOM and then onto the PCMthe locations of the connectors along the path from VSS to 4WABS and up to Instr Cluster & PSOM are;

C404 VSS On rear axle sensor (A7) Terminals: 02

C205 LH rear of engine compartment, in safety wall (Fire Wall) Terminals: 24 In-Line

C202F & M LH rear of engine compartment, in safety wall (A8) Terminal: 7 In-Line

C119 LH front corner of engine compartment on 4WABS control module (E10),Terminals: 40

O/LB to:

C202F & M LH rear of engine compartment, in safety wall (A8) Terminal: 7 In-Line

C252 Programmable Speedometer/Odometer Module (PSOM), Behind top LH side of I/P, on PSOM (A7) Terminal: 12 Color: B at Pins 4

LG/Y to Splice S107 Engine control sensor harness, from C119 near T/O to G101 (G101 RH side of Radiator support); to PSOM Pin 5

C202 F and M

and spliced to Ground G100 (BK)

G100 & G104 (tied together in diagram) G100 @ LH front of engine compartment, on upper radiator support

G100 Serves Component:

Fuel Pump Module

Inertia Fuel Shutoff

Misfire Sensor

Misfire Sensor Shield

Output Shaft Speed (OSS) Sensor

Powertrain Control Module (PCM), 5.0L

From PSOM Pin 7 (GY/BK) to Splice S246 Main harness, near T/O to speed control amplifier to

C185 PK/O @ PCM 5.0L Powertrain Control Module (PCM) LH side of safety wall, on powertrain control module (PCM) (C10) Terminal: 104 Color: GY

C185, 5.8L Powertrain Control Module (PCM) LH side of safety wall, on powertrain control module (PCM) (C10) Terminal: 104 Color: GY

C185 @PCM to C202 F and M

Splice 216 to Ground G200, Instrument Cluster ground is inside passenger side kick panel

and on to C185 @ PCM PIN 58 (GY/BK) and from Pin 46 to MLPS (TR) Pin 2

Verify PCM & MLPS wiring & Pin numbers using following WIRING DIAGRAMs by Ford

psom.jpg

PSOM diagram for '96 Bronco. '93-95 similar.

CHECK SPEED INPUT SIGNAL

NOTE: Only wiring harness end of connector is to be probed.

* Connect Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to Pin 4 (speed in ) and Pin 5 (speed in -) of the PSOM connector (C252).

* Does the voltage increase smoothly and continuously from 0 to approximately 3.5 volts as vehicle (driveshaft) speed increases from 0 to 48 km/h (0 to 30 mph)?

OR:

* If available, a frequency counter may be connected to Pin 4 (Speed in ) and Pin 5 (Speed in -).

* Does the displayed frequency of the signal increase smoothly and continuously from 0 to approximately 667 Hz at approximately 48 km/h (30 mph)?

OR:

* If neither a voltmeter nor frequency counter is available, vehicle speed control may be used as a good indicator. If it works normally, then the speedometer module is at least receiving a speed input signal and the wiring and sensor can be assumed to be good.

VSS Sensor (Rear axle sensor) should read 800-1400 Ohms across the pins, and more than 10 Ohms from the metal shell to either pin \\

bad 4WABS Module - It is located below ws wiper fluid/coolant recovery tank. So, the connector can be corroded by leaking fluid

bad PSOM (Speedo)

I jumpered the Module out as Steve & Turbo Ghost describes below.

To bypass the 4WABS module @ it's harness's connector & feed the ABS signal directly to the PSOM,

Disconnect module (under coolant recovery /ws washer tank) & in connector, jumper LG/Bk to LG/Y, and R/Pk to O/LB..."

Source: by Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/170517_1

Pin numbers are shown in the wiring diagram

or with a pic of the connector and jumpers; Continuity Test Through 4WABS Module Connector in 93-96; "...jumper 14 (CKT 530, LG/Y) to 21 (CKT 519 (LG/BK) & 39 (CKT 491 (O/LB) to 22 (CKT 523, R/PK)...";

Source: by Turbo Ghost at

http://img.photobucket.com/albums/v252/turboghost/ABSConnectorw-jumpers.jpg

Speed Input Signal Test @ PSOM in 93-96 Bronco; "...NOTE: Only wiring harness end of connector is to be probed. * Connect Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to Pin 4 (speed in ) and Pin 5 (speed in -). * Does the voltage increase smoothly and continuously from 0 to approximately 3.5 volts as vehicle speed increases from 0 to 48 km/h (0 to 30 mph)? OR: If available, a frequency counter may be connected to Pin 4 (Speed in ) and Pin 5 (Speed in -). Does the displayed frequency of the signal increase smoothly and continuously from 0 to approximately 667 Hz at approximately 48 km/h (30 mph)? OR: * If neither a voltmeter nor frequency counter is available, vehicle speed control may be used as a good indicator. If it works normally, then the speedometer module is at least receiving a speed input signal and the wiring and sensor & tone ring can be assumed to be good.

This is tuff to do; suggest using str8 pins to back probe the connector

================

For reference purposes:

PSOM Pointer PSOM Pointer Waiver TSB 96-21-11 for 92-96; "..The speedometer needle may waver and or a light surge may occur on some vehicles..." read more

Source: by Ford via miesk5 @ http://home.comcast.net/~miesk5/tech..._bulletins.htm

This also addresses the tone ring & PSOM unit

EXCERPT; ISSUE: The speedometer needle may waver and/or a light surge may occur on some vehicles when speed control is used at highway speeds between 80-113 km/h (50-70 mph). This may be due to slight dents/chips in either the exciter ring or the Vehicle Speed Sensor (VSS) and air gaps between the VSS and the exciter ring.

ACTION: Replace the Programmable Speedometer/Odometer Module (PSOM) if required. New PSOM's come with increased immunity to system variability. Refer to the following Diagnostic Procedure for details.

DIAGNOSTIC PROCEDURE

BRONCO/F-SERIES - Perform normal PSOM diagnostics per Pinpoint Tests "H" and "J" of the 1996 F-Series/Bronco Body/Chassis Service Manual, Pages 13-01-30 through 13-01-32 and Pinpoint "B" of the 1996 Powertrain/Drivetrain Service Manual, Page 10-03-11.

Any slight dents, chips, etc., in either the exciter ring or VSS Sensor will create needle waver. Measure air gap between the VSS and exciter ring. It should be 0.38-0.51mm (0.015-0.020"). Check exciter ring runout per the same ring gear backface runout procedure of the appropriate model 1996 Powertrain/Drivetrain Service Manual, Section 05-00. Make sure the exciter ring is mounted correctly to the ring gear. If runout is more than 0.1mm (0.004"), perform the differential runout check per the procedure in the appropriate model 1996 Powertrain/Drivetrain Service Manual, Section 05-02A or 05-02D, to find cause and repair as needed

Tone Ring Inspection; some pull VSS Sensor off and inspect tone ring teeth for obvious damage...

Tone Ring Inspection; "Take off the rear diff cover. Check the Ring Tone gear. It is located on the left hand side of the ring gear. Look to see if any of the teeth have been notched (from debris floating around in the diff.) Usually a spider gear. If the ring tone gear has been notched, it will need to be replaced to fix your speedo reading. Jack it up and rotate the tires to look for the teeth to be notched/broken/bent..."

Source: by Bighibbi

Defective VSS; "... Anyway, the autozone VSS looks almost identical to the ford VSS. They are both now made of plastic. You have to look very closely to see minor differences. However, the magnet inside does not budge in the ford part, no rattling noise at all. The Autozone part rattles when shaken, ie. the magnet has room to move inside the plastic housing.[/b]It's was a big lesson for me. Wrong readings from the VSS can cause so much E4OD problems...erratic shifting, late shifting, hard shifting, feeling like it was in neutral, as well as engine cutting off at stop lights---Even if it registers correct readings on your speedometer..."

Source: by bkne40d

 

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