dash got bright then normal - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70' GMC · 08-09-2007, 09:22 PM

it got real bright for a few seconds and then went back to being dim like I had it kinda freaked out for a few seconds then done it a few more times

1LoC10 · 08-09-2007, 09:24 PM

do you have the old style alternator with the external regulator

70' GMC · 08-09-2007, 09:26 PM

could ya tell me where it might be located

70' GMC · 08-09-2007, 10:14 PM

any help would be pretty nice

herb101 · 08-09-2007, 10:17 PM

regulator is on the radiator core support on the drivers side, near the horn. Usually silver or gold colored with an inline 4 wire connector.

Dash lights are fed through a nichrome wire rheostat (variable resistor) built into the headlight switch. It's basically a long coil spring of bare wire bent into an arc. There is a wiper contact attached to the knob shaft so that when you turn the headlight switch, the contact runs along the bare coil, getting closer or father from the voltage source and decreasing or increasing resistance. If the switch is old, the coils can short against each other when bumped (like a dip in the road or speedbump), or you could have fried a spider who happened to short a few coils and temporarily decrease the resistance (til he smoked).

Herb

**Stocker** · 08-09-2007, 10:35 PM

Quote:

Originally Posted by herb101

Dash lights are fed through a nichrome wire rheostat (variable resistor) built into the headlight switch.

Or it may be very dirty in there -- try twisting it back & forth several times and see if it helps. If you find an opening in the switch, try spraying contact cleaner inside while twisting the knob.

70' GMC · 08-11-2007, 10:26 AM

last night it did it again got real bright then the speedometer said 35 then it just hit 70 and then went back to 35

**Stocker** · 08-11-2007, 11:22 AM

I take it you have electric speedometer instead of the stock cable-driven speedo?

ChevLoRay · 08-11-2007, 11:55 AM

Oh yeah, I got real bright one time....then got married. Later, divorced her. I found I had gotten brighter and "saw the light".

Regulator...alternator...really the only variables in the electrical system that could cause such actions. Battery is going to assume a profile that will be at a level of charge or discharge. Make sure the alternator belt is tight. That's a freebie you can do, just to be sure....if you haven't already done it.

Andy4639 · 08-11-2007, 03:02 PM

External voltage regulator will cause this to happen also. It will momentarly stick when the charge is feeding it. It is consistly changing amperage and volts depending on your speed.
It's located on driver side of front fender by the horn. It's bolted to the radiator support. Black box with about 7 wires coming out of it.

msgross · 08-11-2007, 03:12 PM

Look below you window washer tank, if there is a square black box with a harnass plugged into it then you have an externally regulated alternator. This black box tells the alternator how much power to put out. They normally go bad and cause the alternator to be high or low and then finally burn itself out. If it keeps doing this then I would suggest the easy upgrade in the link I posted below. You will bypass the external regulator and purchse a new internal regulated alternator ($75). Mine went bas and was feeding 17 volts to everything! This includes your radio, electric choke, wipers, lights etc.... You can see how it can cause issues. You can also buy a new regulator and plug it in but most guys bypass it. Good luck...

Here's the link
http://67-72chevytrucks.com/vboard/s...d.php?t=119379

70' GMC · 08-11-2007, 05:21 PM

got new regulator and a new external voltage regulator for a little under $55 bucks and they came from NAPA

msgross · 08-11-2007, 05:30 PM

cool, hope it fixes your issue...

i'm gonna do the upgrade so I can go to the 94 amp alternator...

RANDY COX · 08-11-2007, 09:12 PM

If you change and make the upgrade you WON'T be sorry I changed mine and now the LIGHTS STAY BRIGHT.My 66 Impala SS use to do the same thing hit the brakes and bam the lights go dim.

cst70rocket · 08-12-2007, 08:21 PM

Mine went bad one night coming in one night, don't know how much it was putting out, but the headlights were so bright my buddy stood in front of the truck and I could see what he had for dinner!!

70' GMC · 08-13-2007, 07:24 AM

it got kinda bright last night and cut off im thinking its the carb problably cause its not getting the gas

08-09-2007, 09:22 PM	#1
70' GMC HERE.......Somewhere Join Date: Oct 2006 Location: Birmingham AL Posts: 2,488	dash got bright then normal it got real bright for a few seconds and then went back to being dim like I had it kinda freaked out for a few seconds then done it a few more times __________________ Current rides: 2013 Hyundai elantra gt DD 1995 camaro my first crush lmao Was: 1970 with a 350 4barrel and 288 horses Classics make it possible!

08-09-2007, 09:24 PM	#2
1LoC10 Insert Title Here Join Date: Feb 2006 Location: Dyer, Indiana Posts: 5,679	Re: dash got bright then normal do you have the old style alternator with the external regulator __________________ BOBBY _69 SWB_ 1000 pics of 67-72's>> http://s193.photobucket.com/albums/z...-72/?start=all <<

08-09-2007, 09:26 PM	#3
70' GMC HERE.......Somewhere Join Date: Oct 2006 Location: Birmingham AL Posts: 2,488	Re: dash got bright then normal could ya tell me where it might be located __________________ Current rides: 2013 Hyundai elantra gt DD 1995 camaro my first crush lmao Was: 1970 with a 350 4barrel and 288 horses Classics make it possible!

08-09-2007, 10:14 PM	#4
70' GMC HERE.......Somewhere Join Date: Oct 2006 Location: Birmingham AL Posts: 2,488	Re: dash got bright then normal any help would be pretty nice __________________ Current rides: 2013 Hyundai elantra gt DD 1995 camaro my first crush lmao Was: 1970 with a 350 4barrel and 288 horses Classics make it possible!

08-09-2007, 10:17 PM	#5
herb101 Used Register Join Date: May 2005 Location: Live Oak, TX Posts: 379	Re: dash got bright then normal regulator is on the radiator core support on the drivers side, near the horn. Usually silver or gold colored with an inline 4 wire connector. Dash lights are fed through a nichrome wire rheostat (variable resistor) built into the headlight switch. It's basically a long coil spring of bare wire bent into an arc. There is a wiper contact attached to the knob shaft so that when you turn the headlight switch, the contact runs along the bare coil, getting closer or father from the voltage source and decreasing or increasing resistance. If the switch is old, the coils can short against each other when bumped (like a dip in the road or speedbump), or you could have fried a spider who happened to short a few coils and temporarily decrease the resistance (til he smoked). Herb

08-11-2007, 10:26 AM	#7
70' GMC HERE.......Somewhere Join Date: Oct 2006 Location: Birmingham AL Posts: 2,488	Re: dash got bright then normal last night it did it again got real bright then the speedometer said 35 then it just hit 70 and then went back to 35 __________________ Current rides: 2013 Hyundai elantra gt DD 1995 camaro my first crush lmao Was: 1970 with a 350 4barrel and 288 horses Classics make it possible!

08-11-2007, 11:22 AM	#8
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,728	Re: dash got bright then normal I take it you have electric speedometer instead of the stock cable-driven speedo? __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

08-11-2007, 11:55 AM	#9
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: dash got bright then normal Oh yeah, I got real bright one time....then got married. Later, divorced her. I found I had gotten brighter and "saw the light". Regulator...alternator...really the only variables in the electrical system that could cause such actions. Battery is going to assume a profile that will be at a level of charge or discharge. Make sure the alternator belt is tight. That's a freebie you can do, just to be sure....if you haven't already done it. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

08-11-2007, 03:02 PM	#10
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: dash got bright then normal External voltage regulator will cause this to happen also. It will momentarly stick when the charge is feeding it. It is consistly changing amperage and volts depending on your speed. It's located on driver side of front fender by the horn. It's bolted to the radiator support. Black box with about 7 wires coming out of it. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

08-11-2007, 03:12 PM	#11
msgross Registered User Join Date: Jul 2006 Location: Central PA Posts: 12,201	Re: dash got bright then normal Look below you window washer tank, if there is a square black box with a harnass plugged into it then you have an externally regulated alternator. This black box tells the alternator how much power to put out. They normally go bad and cause the alternator to be high or low and then finally burn itself out. If it keeps doing this then I would suggest the easy upgrade in the link I posted below. You will bypass the external regulator and purchse a new internal regulated alternator ($75). Mine went bas and was feeding 17 volts to everything! This includes your radio, electric choke, wipers, lights etc.... You can see how it can cause issues. You can also buy a new regulator and plug it in but most guys bypass it. Good luck... Here's the link http://67-72chevytrucks.com/vboard/s...d.php?t=119379 __________________ The Garage: 1968 K-10 SWB - "Project Money Pit" 1996 Z-71 - "huntin rig" 1969 C-10 LWB (SOLD) "Project flip that truck or else" 1993 Passport, F@rd 1-ton (SOLD)"Project Cousin Eddie" My Garage Build "The 1,000 footer"

08-11-2007, 05:21 PM	#12
70' GMC HERE.......Somewhere Join Date: Oct 2006 Location: Birmingham AL Posts: 2,488	Re: dash got bright then normal got new regulator and a new external voltage regulator for a little under $55 bucks and they came from NAPA __________________ Current rides: 2013 Hyundai elantra gt DD 1995 camaro my first crush lmao Was: 1970 with a 350 4barrel and 288 horses Classics make it possible!

08-11-2007, 05:30 PM	#13
msgross Registered User Join Date: Jul 2006 Location: Central PA Posts: 12,201	Re: dash got bright then normal cool, hope it fixes your issue... i'm gonna do the upgrade so I can go to the 94 amp alternator... __________________ The Garage: 1968 K-10 SWB - "Project Money Pit" 1996 Z-71 - "huntin rig" 1969 C-10 LWB (SOLD) "Project flip that truck or else" 1993 Passport, F@rd 1-ton (SOLD)"Project Cousin Eddie" My Garage Build "The 1,000 footer" Last edited by msgross; 08-11-2007 at 05:31 PM.

08-11-2007, 09:12 PM	#14
RANDY COX Registered User Join Date: Mar 2001 Location: RADFORD, VA Posts: 2,651	Re: dash got bright then normal If you change and make the upgrade you WON'T be sorry I changed mine and now the LIGHTS STAY BRIGHT.My 66 Impala SS use to do the same thing hit the brakes and bam the lights go dim. __________________ 1964 BBC 402 4x4

08-12-2007, 08:21 PM	#15
cst70rocket Registered User Join Date: Sep 2005 Location: San Angelo or Eufaula Posts: 301	Re: dash got bright then normal Mine went bad one night coming in one night, don't know how much it was putting out, but the headlights were so bright my buddy stood in front of the truck and I could see what he had for dinner!!

08-13-2007, 07:24 AM	#16
70' GMC HERE.......Somewhere Join Date: Oct 2006 Location: Birmingham AL Posts: 2,488	Re: dash got bright then normal it got kinda bright last night and cut off im thinking its the carb problably cause its not getting the gas __________________ Current rides: 2013 Hyundai elantra gt DD 1995 camaro my first crush lmao Was: 1970 with a 350 4barrel and 288 horses Classics make it possible!



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