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lighting issues


MarcosLopez77

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1991
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Ok So I have a 1991 Ranger that im having some lighting issues.

First problem is the Dome Light. Light works perfectly fine when the doors open but when I turn it on manually with the switch it doesn't. the same switch also controls the cargo lamp so both are supposed to turn on together. Cargo lamp turns on with switch but no Dome. I replaced the switch and the electrical plug from a parts truck that I have. the old plug was kind of melted in some areas for whatever reason so I assumed that would be the problem. After replacing switch and plug I still have the same issue. Which leads me to believe that the wire between the switch and light might be the culprit?



Second Problem is when the truck is running all lights (headlights, taillights, dash lights seem to flicker with the trucks idle. improves some when accelerating. Any ideas what would cause this the lights to do this?

thank you in advance. any help is greatly appreciated.

My apologies for the duplicate post, wasn't sure if this belonged on this page or electrical page.
 


RonD

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Not sure about the dome light, is the switch on the dome light unit or are we talking about the switch on the dimmer/master light switch?

An Alternator has 3 Fields that produce AC voltage, each Field has a set of Diodes that convert the AC to DC volts.
It is not unusual for 1 field to fail, fully or partially, this can produce flickering or dimming lights at idle when the lower rotational speed of alternator requires voltage regulator to run full power thru the fields.

Best thing is to measure the battery voltage at 1,000rpms then at idle. 650-750rpms
After initial startup recharge, 14+ volts, the voltage regulator will try to maintain 13.6volts regardless of RPMs or electric load.

So with engine idling and voltage meter showing 13.6v, start turning on lights, heater fan blower, radio, dome light :), kidding, ect......
And watch voltage meter, voltage should drop and then come back in a second or two, that is the voltage regulator reading the extra power draw and then compensating for it.
If voltage starts dropping below 13.6v and not coming back up at full load then a field has been lost.
Increase RPMs and see if 13.6v is maintained again.

Since you don't spend much time idling you can run on 2 fields for a long time so totally your choice if you want to replace alternator.
 

MarcosLopez77

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1991
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Manual
RonD said:
Not sure about the dome light, is the switch on the dome light unit or are we talking about the switch on the dimmer/master light switch?

An Alternator has 3 Fields that produce AC voltage, each Field has a set of Diodes that convert the AC to DC volts.
It is not unusual for 1 field to fail, fully or partially, this can produce flickering or dimming lights at idle when the lower rotational speed of alternator requires voltage regulator to run full power thru the fields.

Best thing is to measure the battery voltage at 1,000rpms then at idle. 650-750rpms
After initial startup recharge, 14+ volts, the voltage regulator will try to maintain 13.6volts regardless of RPMs or electric load.

So with engine idling and voltage meter showing 13.6v, start turning on lights, heater fan blower, radio, dome light :), kidding, ect......
And watch voltage meter, voltage should drop and then come back in a second or two, that is the voltage regulator reading the extra power draw and then compensating for it.
If voltage starts dropping below 13.6v and not coming back up at full load then a field has been lost.
Increase RPMs and see if 13.6v is maintained again.

Since you don't spend much time idling you can run on 2 fields for a long time so totally your choice if you want to replace alternator.
Click to expand...
RonD thank you for your reply. Sounds like I need to check my alternator. I have noticed the voltage regulator is usually reading kinda high. not really right in the middle like normal. as far as the dome switch its on the master switch that also operates dimmer and headlights
 
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