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Alternator Problems


stevedohc2b

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Hi

 

i have a zetec with a small denso type alternator and broke down the other week with no charge going to battery.

 

fitted a new alternator seamed to solve the problem then after a 2 mile test drive the volts dropped down to 12 and no charge to the battery.

 

I had added some led driving lights before this happened and put MOT miles on before i broke down on a 100 mile run

 

Took off and had both bench rig tested and no output. So fitted a new reg removed led lights feed,too no 2 and still no joy.

 

how can i further bench test

 

i have diode tested the rectifier in place and only reads one way

 

help may be in the tin top at w/e

 

Stephen

 

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Had a further thought last night. I think you said the new lights were added to the same fuse as supplied the ignition light. My thought was that there are usually two unfused circuits on old cars. Ignition coil is one and ignition light is the other, both switched lives and unfused.

Priority is to check continuity of supply through ignition light, second ignition live to alternator and continuity of the main alternator lead to battery. Usefull tip is to remove the exciter lead from the alternator, extend it with a flying lead, ignition on. The ignition light should be off. Touch the end of the flying lead to the battery neg. Light on. Touch the end of the flying lead to the battery pos. Light off. No smoke at any time. Shows it's working as intended.

 

Nigel

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Does the battery fully charge on a 240volt home charger,& if OK what do the battery volts drop to when cranking the kit engine ? The battery plates may be oxidised preventing electric flow from alternator & then back out to starter.

Maybe test specific gravity of each battery cell if this is possible, modern batteries may be an "improvement" but how do you test for a faulty cell/check electrolyte level if no cell caps.

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( Usefull tip is to remove the exciter lead from the alternator, extend it with a flying lead, ignition on. The ignition light should be off. Touch the end of the flying lead to the battery neg. Light on. Touch the end of the flying lead to the battery pos. Light off. No smoke at any time. Shows it's working as intended.)

 

Nigel do you mean the warning light not the ignition live exciter lead.

 

stephen

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Right Nigel test is all ok

had the battery tested all ok

checked continuity all good.

 

On cranking the battery volts drop to 10.5 volts

 

have made a hot lead for ignition live feed and clamped to battery the dash battery light won't light till this is connected ?

 

gave it a good rev and battery light went out drop revs Bach on and no volt increase at battery.

 

Stephen

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Charging System Diagnosis

 

The following general information has been assembled as a guide for charging system diagnosis. Refer to the appropriate Original Equipment Manufacturers service manual for specific information pertaining to charging system diagnostic procedures and safety precautions for your vehicle.

 

Bench testing

 

If an alternator test bench is available, follow the procedures found in the bench testers instruction manual to conduct an alternator performance test. This test will determine if the alternator output is within its performance specification, preventing unnecessary alternator replacement.

 

If the alternator output is within specification during bench testing, resolve problems in the remainder of the vehicles charging circuit and other electrical circuits that may affect charging circuit performance. Refer to the appropriate vehicle manufacturers service manual for the procedures and circuit schematics necessary to identify and correct additional charging circuit problems.

 

If the test bench results show the alternators output performance to be out of specification, replace the alternator. Follow the vehicle manufacturers recommended procedures to inspect the remainder of the charging circuit and other electrical circuits that may affect charging circuit performance.

 

NOTE: If the bench test identifies the regulator as defective, it may be possible to replace the regulator (internal or external) and return the alternator to service. If the regulator is replaced and the alternator returned to service, follow the vehicle manufacturers recommended procedures to inspect the remainder of the charging system and other electrical circuits that may affect charging circuit performance.

 

Whether or not a test bench was used to determine the condition of the alternator, the following Helpful Tips have been assembled to help isolate conditions that may affect charging circuit performance.

 

Helpful Tips

 

What is the condition of the battery?

A visual inspection and a performance test of the battery must always be performed before inspecting the charging system. The battery must be fully charged (12.6 volts) and the battery cables, terminals and case in good, clean condition. This includes the frame and body grounds as well (refer to Battery Visual Inspection and Performance Testing).

 

Does a charge lamp, amperage (amp) gauge or voltmeter indicate a charging system problem?

Charge Lamp:

Ignition ON engine not running

The charge lamp should illuminate.

Ignition ON engine running

The charge lamp should illuminate briefly then turn OFF.

Weak Battery

A weak battery can cause the charge lamp to illuminate during high amperage draw.

Low Idle

A low idle can cause the charge lamp to illuminate dimly.

Poor Wiring

Corroded, broken, loose or frayed wires/ connections could cause the charge lamp to illuminate during idle.

Open Charge Lamp

Some charging systems will not properly operate if the charge lamp bulb fails.

Amp Gauge:

Ignition ON engine not running

The amp gauge should read zero or slightly below.

Ignition ON engine running

The amp meter should display a current output above zero. It will display a different level of charge depending on what electrical circuits are operating. A negative charge indicates the battery is discharging more quicklythan the charging system can supply current.

Wires and connectors

Corroded, broken, loose or frayed wires/connections could cause zero or erratic readings on the gauge.

Voltmeter:

Ignition ON and engine not running

Gauge readings should be between 12.0 and 12.6 volts with the ignition ON and the engine not running. Readings below 12 volts could indicate insufficient charging, low battery, corroded,

broken, loose or frayed wires/connections.

Ignition ON and engine running

Gauge readings should be between 13.0 and 14.5 volts with the ignition ON and the engine running. A reading exceeding 14.5 volts could indicate a bad battery, failed regulator or poor wire

connections. A reading below 13.2 volts could indicate a failed alternator or corroded, broken, loose or frayed wires/connections.

 

Are any fuses open?

Check the fuses in all the fuse box(es). An open fuse indicates circuit problem(s) that may have an effect on the charging circuit. Check the owners manual or the manufacturers service manual for the location of each fuse box.

 

Is the fusible link(s) open?

There may be several fusible links controlling

battery voltage to the vehicles electrical circuits. If a fusible link is open, supply voltage will be completely lost to all electrical systems or to the electric circuit(s) that the open fusible link controls. Check the owners manual or the manufacturers service manual for the location of each fusible link.

 

Is the alternators drive belt tension within specification?

Too loose

If the drive belt is too loose, it will slip around the pulley causing the alternator to charge irregularly or not at all.

Too tight

If the drive belt is too tight, internal bearing damage will cause premature alternator failure.

 

Is the alternators drive belt in good condition and the proper size?

Worn or too narrow

If the alternators drive belt is worn or too narrow, it will slip around the pulley, causing the alternator to charge irregularly or not at all.

New drive belt

The life of a new alternator drive belt is approximately 10 minutes. It is important to check and adjust the belts tension to the used specification after the initial 10 minutes of operation.

 

Has the vehicle been modified or additional equipment installed after it left the factory?

Accessories

Non-factory accessories such as phones, computer outlets, televisions, refrigerators, stereo equipment or lights, among others, can overburden alternator performance and cause premature failure.

Improper accessory installation

Improper accessory installation procedures can cause charging problems. Some of these problems may include poor ground points, loose connections or improper wiring.

 

Has any work been performed on the vehicle?

Electrical ground points

Check the ground circuits between the battery and engine and also from the vehicle body to the frame for high resistance. Many times when a vehicle has been repaired, the ground point(s) are disturbed or not re-secured properly.

Multiple electrical grounds

With multiple ground vehicles, each electrical circuit is assigned to one or more ground points. A poor ground at one ground point may cause feedback through another ground point causing unusual circuit activity.

Just a generic sheet we used to give to the apprentices HTH

 

 

 

 

 

 

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Hi nigel

I have checked the Lead back to battery and have continuity using the original Ford cable.

 

I was thinking of rewiring this to the starter motor and also rewiring the ignition feed what fuse should I use for this.

 

Where could I get a new fused ignition feed from.

 

stephen

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If you have continuity of the cable from B+ on alternator to battery pos then that's all you need. I think ford abandoned the fusible link in this cable (but not having bought a ford in 20 years I don't know for sure.). It was a safety feature that caused more breakdowns than it solved.

I don't know which denso you have. See pic below. As has been said they need an ignition live supply and an ignition lamp supply to two of the small terminals. Examples below. I wouldn't fuse either.

 

Nigel

 

ps there's always the possibility that the original alternator died of old age and the replacement was faulty. £10 from the local scrappy would check that out.

post-21-0-65711500-1461751219_thumb.gif

Edited by Longboarder
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