DRL Problem. Not a question just FYI - The 1947 - Present Chevrolet & GMC Truck Message Board Network

speedygonzales · 12-07-2010, 10:14 AM

Wanted to give all Y'all a heads up on a DRL problem I had noticed on Saturday. Everything appeared normal, green indicator on the dash worked and went out when it was supposed to. Low beams worked when the switch was turned to headlights. But the DRL's were not on when they were supposed to be.

Checked number 15 fuse was good. Checked the DRL relay contact point at the socket. Labeled G6 in the drawing:
http://carphotos.cardomain.com/ride_...4003_large.jpg

No power at the socket. I knew at that point it had to be the diode labeled 203 in the above drawing.

The problem is finding the diode. Shown what it looks like here:
http://carphotos.cardomain.com/ride_...4002_large.jpg

here's a view of under the dash looking for it.
http://carphotos.cardomain.com/ride_...4004_large.jpg

The diode is under the dash almost directly in line with the radio. The bracket it's attached to is bolted to the crossbar under the dash. So look for the fins on the heat sink first. Then you can get the bolt out which is oddly angled up toward the airduct right next to it.

I decided to not bolt it back into it's place. Just tie wrapped it in place. Back to the story.

After getting it out, I tested it with an ohm meter and noticed it was good. However the terminals had a little green corrosion on them. Cleaned them off, and packed it with dielectric grease and put it back together. Works fine. NO parts needed. No money spent.
Here's a view of the connector
http://carphotos.cardomain.com/ride_...4001_large.jpg

NOTE: A couple of things I noticed that I did not like. First, the female contacts that connect to the diode connector are the type that are just folded over. Not the normal rolled end type slip-ons that you see at the auto parts store. They are relying on a flat surface to flat surface contact. Rather than the better rolled edge of the female that "digs" into the male pin for a better contact.

The other thing I noticed when looking at the fuses is they appear to have tarnish like silver flatware does.

This brings a couple of items to everyone's attention.
Even though a fuse is good. It doesn't mean it is making good contact with the mating contacts. So it's a good idea to pull them out and reseat them.

The other is, many would have gotten a replacement diode ($26 local dealer) and simply plugged it in and went on their way. They would have thrown the old one away and assumed it was bad and the new one fixed the problem.

When in fact the problem wasn't a functional problem but merely a contact problem. With a little more searching they could save them the cost of the parts.

The other thing is, I bought the truck new in Dec of 98. Just now it has a contact problem after 12 years so all Y'all with these vintage vehicles be on the look out for contact issues and don't just throw parts at the problem.

If any of you need help with electrical issues, let me know. I have the shop manual that applies to units from 96 - 99 (old style in 99).

ChevLoRay · 12-08-2010, 12:11 AM

This info is going to help someone....at some time. You bring up some good points about electrical systems. Primarily, the circuit is only as good as the connectors. Any junction within any circuit is a potential troublespot. Poor connections, with sufficient current can arc. That arcing will eventually burn the connector. Add in the possibility of corrosion from the enviroment and your situation is a possibility, as you described.

The electronic systems of these trucks will deteriorate over time....and the newest of this series of trucks is 12 years old, while the oldest ones date from mid-1987, making them almost 24 years on the roads. In 2013, those '88 model trucks will be Antiques, at least in Arkansas.

speedygonzales · 06-03-2011, 02:28 PM

Seems the fix was not good enough. Had to re terminate the wires and reconnect to the diode. Cleaning the inferior connections that were there was not enough.

Ended up having to solder the connections at the diode.

Update to the update.
Even soldering did no good. Had to reterminate the wires and get a new diode. So far lasting.

12-07-2010, 10:14 AM	#1
speedygonzales Registered User Join Date: Jan 2006 Location: Smithfield, VA Posts: 1,501	DRL Problem. Not a question just FYI Wanted to give all Y'all a heads up on a DRL problem I had noticed on Saturday. Everything appeared normal, green indicator on the dash worked and went out when it was supposed to. Low beams worked when the switch was turned to headlights. But the DRL's were not on when they were supposed to be. Checked number 15 fuse was good. Checked the DRL relay contact point at the socket. Labeled G6 in the drawing: http://carphotos.cardomain.com/ride_...4003_large.jpg No power at the socket. I knew at that point it had to be the diode labeled 203 in the above drawing. The problem is finding the diode. Shown what it looks like here: http://carphotos.cardomain.com/ride_...4002_large.jpg here's a view of under the dash looking for it. http://carphotos.cardomain.com/ride_...4004_large.jpg The diode is under the dash almost directly in line with the radio. The bracket it's attached to is bolted to the crossbar under the dash. So look for the fins on the heat sink first. Then you can get the bolt out which is oddly angled up toward the airduct right next to it. I decided to not bolt it back into it's place. Just tie wrapped it in place. Back to the story. After getting it out, I tested it with an ohm meter and noticed it was good. However the terminals had a little green corrosion on them. Cleaned them off, and packed it with dielectric grease and put it back together. Works fine. NO parts needed. No money spent. Here's a view of the connector http://carphotos.cardomain.com/ride_...4001_large.jpg NOTE: A couple of things I noticed that I did not like. First, the female contacts that connect to the diode connector are the type that are just folded over. Not the normal rolled end type slip-ons that you see at the auto parts store. They are relying on a flat surface to flat surface contact. Rather than the better rolled edge of the female that "digs" into the male pin for a better contact. The other thing I noticed when looking at the fuses is they appear to have tarnish like silver flatware does. This brings a couple of items to everyone's attention. Even though a fuse is good. It doesn't mean it is making good contact with the mating contacts. So it's a good idea to pull them out and reseat them. The other is, many would have gotten a replacement diode ($26 local dealer) and simply plugged it in and went on their way. They would have thrown the old one away and assumed it was bad and the new one fixed the problem. When in fact the problem wasn't a functional problem but merely a contact problem. With a little more searching they could save them the cost of the parts. The other thing is, I bought the truck new in Dec of 98. Just now it has a contact problem after 12 years so all Y'all with these vintage vehicles be on the look out for contact issues and don't just throw parts at the problem. If any of you need help with electrical issues, let me know. I have the shop manual that applies to units from 96 - 99 (old style in 99). __________________ 99 Z71 (98 body style) Pride and joy Last edited by speedygonzales; 12-07-2010 at 10:23 AM.

12-08-2010, 12:11 AM	#2
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: DRL Problem. Not a question just FYI This info is going to help someone....at some time. You bring up some good points about electrical systems. Primarily, the circuit is only as good as the connectors. Any junction within any circuit is a potential troublespot. Poor connections, with sufficient current can arc. That arcing will eventually burn the connector. Add in the possibility of corrosion from the enviroment and your situation is a possibility, as you described. The electronic systems of these trucks will deteriorate over time....and the newest of this series of trucks is 12 years old, while the oldest ones date from mid-1987, making them almost 24 years on the roads. In 2013, those '88 model trucks will be Antiques, at least in Arkansas. __________________ 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.

06-03-2011, 02:28 PM	#3
speedygonzales Registered User Join Date: Jan 2006 Location: Smithfield, VA Posts: 1,501	Update on this situation Seems the fix was not good enough. Had to re terminate the wires and reconnect to the diode. Cleaning the inferior connections that were there was not enough. Ended up having to solder the connections at the diode. Update to the update. Even soldering did no good. Had to reterminate the wires and get a new diode. So far lasting. __________________ 99 Z71 (98 body style) Pride and joy Last edited by speedygonzales; 06-22-2011 at 06:48 AM.



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