1999 GMC Yukon Gremlins

[bertsaxby]

First 99 Yukon is one of the 'transitional' years, actually an unmarked 'Denali' 4WD. Denali packages

were apparently just a trim level at this point. Only reason I know its a Denali is everytime the VIN gets

pulled it shows as Denali. In any case, this Yukon still favors the 98 and prior GMC Trucks, even has the 1500

branded across the side. Recently I have been having an issue with my battery losing charge. My alternator and

battery have been replaced with new units, both were tired anyway. All was well for awhile but my battery is still

draining. Today I noted that the instrument gauges are still reading even though the key

is in the off position. I also noted today that if the headlights are switched on the LED's on

the clock radio shut off, not dim, actually off. I am also getting random motor sounds from the AC vent flaps. Any assistance

with troubleshooting appreciated.

[Motor City Rick]

When these issues are going on with key out of the ignition, open the drivers door. Did anything change?

 

Second, see if somebody can read BCM / Body codes if available. That would help you a lot. Record those codes for this blog. As a "longshot" disconnect the battery overnight. Reconnect to see if anything changed.

 

Third, I hope you bought "the biggest" amp alternator / or the largest Cold Cranking Amp (CCA) battery you can put on your truck.

I think you have a current draw issue along with BCM losing control with what it has to do..

Find a digital volt ohm meter (DVOM), remove the positive battery cable. Install a 3/8's short bolt (1 to 1 1/4 inch or so) with 16 treads per inch (coarse thread). Install bolt into battery terminal fitting snuggly. Make sure it doesn't touch metal / ground.

Make / or get a 14 to 16 gauge jumper wire with alligator clips on both ends. Place jumper wire between positive battery terminal bolt and the disconnected positive battery cable. Make very sure the connection at the battery cable end is very good and not loose. Connect to the actual cable, not the cable mount bolt. If you have to, stick a very small straight blade screw driver under the red insulation and connect with the alligator clip. The reason for this is to set all the delay modules items to sleep. This could take up to 3 minutes. Make sure vehicle is off, no keys in the ignition, all doors are closed.

Next step, set DVOM to the "20 or 10 amp" (not volts) scale. Connect the DVOM alligator clips the same way as stated earlier next to the jumper wire set up. Wait for 2 to 3 minutes for delay modules to fall asleep. After that time has passed, disconnect the "jumper wire". The DVOM should read 0.900 amps or less. If it reads more like 1.50 amps or more, you have current draw issue. The rule of thumb is find your Cold Cranking Amp (CCA) value, I.E. 725 CCA, then your current draw on the DVOM cannot exceed 0.725 milliamps. If it is much higher, like 1.5 amps or higher, you have a current draw issue. Don't be afraid to repeat this test. Sometimes a loose connection reawakens delay modules to full use which will be higher amperage.

If current draw readings are little bit higher, look at glove box light, some courtesy light on. Some accessory left on etc.

If your amperage is much higher, disconnect "ALL" non factory stuff to see if the amperage drops. Any non factory accessories should be powered through relays controlled by ignition on voltages, not battery voltages which could cause current draw.

I will need "accurate readings" from your DVOM for this test along with the rated amperage output of the alternator and cold cranking amps of the battery. Tell me what the battery voltage is after the vehicle sits overnight or longer, not charged. Tell me like 24 hours / 12.4 volts at Bat terminals. For current draw, 0.000 amps to 4.350 amps as an example.

Good luck, will be waiting for the data.

[bertsaxby]

Thanks Rick. Nothing changes with the door open or closed. I smacked the dash near the fuse panel and now the door buzzer and lights are working again. I may pull the fuses and polish the corrosion that seems to be on all of them. That seems to get results on my collector cars with odd electrical problems. There are no 'non-factory' additions to the electrical. I am the only owner and I keep my vehicles stock. I took it into NAPA today and they replaced my battery, dead cell. I took the opportunity to get my alternator tested as well. It was a direct factory part replacement I installed in 2014. There were no issues found with it. I can give you the CCA of the battery and alternator off the NAPA report tomorrow. IIRC the new battery tested at 1128 CCA.

[Motor City Rick]

If your battery dies, starter cranks slow in the next few weeks, you have to look in 2 areas. One being alternator output, other is "current draw" on the electrical system.

 

Good luck!