Generator, temp, brake dash light problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Btc10 · 01-22-2011, 07:28 PM

1970 chevy C10 truck. When I turn my key to the on position my dash lights will not come on but, when I start my truck the generator light comes on and stays on and my brake and temp light never comes on. Does anybody knows whats wrong?

Longhorn Man · 01-22-2011, 08:10 PM

The brake light is only supposed to come on when the key is in the crank position and when there is a hyd. problem. I would check the bulb first if it isn't coming on durring start up.
The Gen light, if it comes on, probably means you aren't charging. I would look into that as soon as possible, even sooner if it is a driver.
It has been so long since I had a truck with the temperature light on it (base model guages only) that I can't remember if it is supposed to come on or not when starting.

Btc10 · 01-23-2011, 02:46 AM

The Bulb is fine. I got my alternator checked and its charging and has the right amount amps. What else can I do?

matt67350 · 01-23-2011, 03:07 AM

check all the ground. The back of the gauge cluster may need a ground.

**VetteVet** · 01-23-2011, 03:50 AM

The brake and temp lights should come on when their wires are grounded with the key on touch the brown wire at the prop valve and the brake light should come on. Do the same with the green wire at the temperature sending unit. The key switch terminal for start also has a ground connection for these two lights so that when the key is turned to the start position it grounds the negative side of the lights and allows them to light up.

The alternator charging light is another matter because it comes on but doesn't go off when it should. Have you checked the voltage output at the large stud on the back of the alternator with the engine running?

It is possible that you do have a grounding issue with the dash or perhaps the wire on the key switch is not grounded. If you check them as I suggested then that will help in the trouble shooting.

**VetteVet** · 01-23-2011, 04:00 AM

Here is a good explanation of how the alternator and the light works. It's possible that the alternator is putting out too much voltage which will cause the light to stay on. That's why I asked what voltage you were getting at the output stud on the back of the alternator. If you are getting more than 15 volts then the regulator or the alternator may be bad.
http://www.alternatorparts.com/under...lternators.htm

Btc10 · 01-24-2011, 07:44 PM

I finally got it. Thanks for everything.

01-22-2011, 07:28 PM	#1
Btc10 Registered User Join Date: Feb 2010 Location: Joshua, Texas Posts: 60	Generator, temp, brake dash light problems 1970 chevy C10 truck. When I turn my key to the on position my dash lights will not come on but, when I start my truck the generator light comes on and stays on and my brake and temp light never comes on. Does anybody knows whats wrong?

01-22-2011, 08:10 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Generator, temp, brake dash light problems The brake light is only supposed to come on when the key is in the crank position and when there is a hyd. problem. I would check the bulb first if it isn't coming on durring start up. The Gen light, if it comes on, probably means you aren't charging. I would look into that as soon as possible, even sooner if it is a driver. It has been so long since I had a truck with the temperature light on it (base model guages only) that I can't remember if it is supposed to come on or not when starting.

01-23-2011, 02:46 AM	#3
Btc10 Registered User Join Date: Feb 2010 Location: Joshua, Texas Posts: 60	Re: Generator, temp, brake dash light problems The Bulb is fine. I got my alternator checked and its charging and has the right amount amps. What else can I do?

01-23-2011, 03:07 AM	#4
matt67350 Registered User Join Date: May 2001 Location: Benbrook, TX Posts: 1,060	Re: Generator, temp, brake dash light problems check all the ground. The back of the gauge cluster may need a ground. __________________ 69 swb stepside, rebuild and upgrade in progress

01-23-2011, 03:50 AM	#5
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,709	Re: Generator, temp, brake dash light problems The brake and temp lights should come on when their wires are grounded with the key on touch the brown wire at the prop valve and the brake light should come on. Do the same with the green wire at the temperature sending unit. The key switch terminal for start also has a ground connection for these two lights so that when the key is turned to the start position it grounds the negative side of the lights and allows them to light up. The alternator charging light is another matter because it comes on but doesn't go off when it should. Have you checked the voltage output at the large stud on the back of the alternator with the engine running? It is possible that you do have a grounding issue with the dash or perhaps the wire on the key switch is not grounded. If you check them as I suggested then that will help in the trouble shooting. __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

01-23-2011, 04:00 AM	#6
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,709	Re: Generator, temp, brake dash light problems Here is a good explanation of how the alternator and the light works. It's possible that the alternator is putting out too much voltage which will cause the light to stay on. That's why I asked what voltage you were getting at the output stud on the back of the alternator. If you are getting more than 15 volts then the regulator or the alternator may be bad. http://www.alternatorparts.com/under...lternators.htm __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

01-24-2011, 07:44 PM	#7
Btc10 Registered User Join Date: Feb 2010 Location: Joshua, Texas Posts: 60	Re: Generator, temp, brake dash light problems I finally got it. Thanks for everything.



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