Dimming dash lights

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

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.

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.

Click to expand...

thanks very much

Do LED bulbs in the dash cluster exhibit the same dimming, or, do they maintain brightness? Just curious if they respond the same way as incandescent bulbs.

I have not noticed this effect in my LEDs.

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

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.

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

Yeah. Don't drive at night.

Seriously, these bulbs were dim way back when. Several folks have upgraded to LEDs with good success.

+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.

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

Click to expand...

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.

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.

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.