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Dimming dash lights


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Hello,

 

Have a 73 convertible 351c, no AC. Notice that at idle dash lights dim a little if I rev the engine or accelerate they brighten. Otherwise the charging system seems to be fine. Cranks rapidly, always starts ... no issues. The alternator appears to be a fairly new aftermarket replacement. The battery really dont know much about. Is this normal or an indication of a problem ? Thanks

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Normal. At idle, the alternator is supplying the battery with power, but not a whole lot. By the time the little electrons reach the dash lamps, many have been trapped at various connectors and converted to heat (voltage drop). Revving the engine brings maximum charge to the battery (14.6V or so) and thus a few more electrons make it to the lamps. Typical voltage at idle around the dash area is 10.5V, when not at idle, it may reach 12.0V.

Let me check your shorts!

http://midlifeharness.com

cactus.jpg.92e5d9d8700abc0ed60c8ccb3426248e.jpg

 

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Normal. At idle, the alternator is supplying the battery with power, but not a whole lot. By the time the little electrons reach the dash lamps, many have been trapped at various connectors and converted to heat (voltage drop). Revving the engine brings maximum charge to the battery (14.6V or so) and thus a few more electrons make it to the lamps. Typical voltage at idle around the dash area is 10.5V, when not at idle, it may reach 12.0V.

 

thanks very much

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  • 1 month later...

Very normal. If you upgrade your alternator to a beefy 100A then you definitely won't see this. Most provide 65-75A at idle. Stock alternators are 35A I think. Other possible issues with crazy lights are the VR and 5V CVR in the gauge cluster.

 

Non-dimmable LEDs shouldn't exhibit any fluctuation is light since they are on/off. I doubt dimmable LEDs would be effected either.

 

KR

-Former 70 & 72 Mustang Owner.

-69 Torino GT, Formal Roof, 351W, Edelbrock 600 cfm, Edelbrock 351W Performer RPM intake, headers, AOD trans, dual flowmasters w/H pipe, Pertronix II Billet, 3.5 TRACLOC g/r, 15" Magnum 500s, 100A alt, aluminum radiator, electric fan, Pro-car seats, mini-starter...owned since Dec 13.

-70 Mach 1, 351W, Edelbrock E-Street EFI, VHX instrument cluster, Hooker headers, dual flowmasters, Pertronix II, 15" Magnum 500s, 150A alt, aluminum radiator, dual electric fans, Pro-car seats, mini-starter

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I have stock 351c, alternator, regulator and at idle no dimming lights. At start up voltage reads 13+ tapped from

positive radio wire.

 

Seems I remember a loose alternator belt would cause that issue.

73 Grande

351C 2v

Now 4v Carb/Cam/headers/T5

 

Gasoline is for washing parts.

Alcohol is for drinking.

Nitomethane is for racing!

 

 

Work in Progress photos here:

Last Update: 4/23/16

 

http://s1270.photobucket.com/user/therocket366/library/?sort=3&page=1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Hello Folks! I am new here and have been going thru the topics to see which ones apply to me. I found this one as my dash lights are extremely dim and they stay like that regardless whether is idling or not.

I have read some of your answers and did not find one that applies to me. My alternator, battery and belts are working properly.

Any suggestions?

Thanks,

Siggy

Ps. 72 Mach 1

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+1 Midlife

 

Dim dash lights are the norm for whatever reason.

 

LED bulbs are an option but they are "ON" or "OFF" no adjusting brightness.

 

I don't drive my car at night much and live with it... however I have aftermarket

gauges for Oil Pressure, temp, and volts that are well lit.

73 Grande

351C 2v

Now 4v Carb/Cam/headers/T5

 

Gasoline is for washing parts.

Alcohol is for drinking.

Nitomethane is for racing!

 

 

Work in Progress photos here:

Last Update: 4/23/16

 

http://s1270.photobucket.com/user/therocket366/library/?sort=3&page=1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Hello Folks! I am new here and have been going thru the topics to see which ones apply to me. I found this one as my dash lights are extremely dim and they stay like that regardless whether is idling or not.

I have read some of your answers and did not find one that applies to me. My alternator, battery and belts are working properly.

Any suggestions?

Thanks,

Siggy

Ps. 72 Mach 1

 

I pulled out the blue diffusers, replaced my headlight switch and swapped out all the bulbs to LEDs and I have great night visibility on my gauges. Jeff73mach1 also has a headlight relay he recommends to take some of the load off the headlight switch. I just use LED headlights.

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  • 4 months later...

I've done the following on a few different cars, but all of these are currently in place on my Torino.

 

a). Removed the blue diffusers (no longer have blue tint)

b). Swapped in LEDs, dimmable.

c). Added headlight relay

d). 100A Alternator

 

On my 72 Mustang I removed the blue diffusers but added little blue autogage covers over the stock bulbs. It brightened it up a bit and left the ability to dim. It also matched the gauges I put in.

 

In retrospect, I recommend (a) and (b) above for a cheap lighting upgrade. You can also get blue LEDs, but I didn't like the tint of blue. © shouldn't be for those without electrical wiring confidence but it was a notable improvement and (d) is the easy but probably won't provide that noticeable of an improvement.

-Former 70 & 72 Mustang Owner.

-69 Torino GT, Formal Roof, 351W, Edelbrock 600 cfm, Edelbrock 351W Performer RPM intake, headers, AOD trans, dual flowmasters w/H pipe, Pertronix II Billet, 3.5 TRACLOC g/r, 15" Magnum 500s, 100A alt, aluminum radiator, electric fan, Pro-car seats, mini-starter...owned since Dec 13.

-70 Mach 1, 351W, Edelbrock E-Street EFI, VHX instrument cluster, Hooker headers, dual flowmasters, Pertronix II, 15" Magnum 500s, 150A alt, aluminum radiator, dual electric fans, Pro-car seats, mini-starter

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I also replaced the old voltage regulator with a new Solid State one, and that was the final piece that fixed any flicker in the lights. I had already done LEDS, alternator, headlight relays.

1972 H-code Mach1

2010 GT Premium

2015 Hyundai Sonata Sport 2.0T

1995 F150- The "home depot" machine

2012 Harley Davidson Road Glide Ultra

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