High Voltage Readings

[merlin1128]

Voltage.... I am getting volatge readings with normal drving around the low 13's... Headlights on I get 14.6 which he said is fine and normal.... Once I turn on the windshield wipers even on intermittent without them moving except once every 10 seconds or so (give or take) voltage goes right up to 14.6 to 14.8 and sits their.... I am not going off the gauge cluster I am going off the OBD with a plug in digital reader, so that is how I am getting exact numbers

Is that normal???? Reason I ask is I have a portable Nav I use because it has live traffice and when I get high voltage readings it shuts down and starts back up... Plus my ****** 9500IX gets very erratic....

Does any of this make any sense to anyone? I am thinking maybe the wiper motor is failing and drawing high volts despite it works? Is this normal when you activate the Wipers to get that high of readings? This thing even sitting still is drawing more volts than the headlights when they are the time. One would think in intermittent it would have no draw because they are not doing anythings

The Tahoe was in during the accident for that speedometer recall and they reprogrameed the computer..... A lot of variables and I hate to spend money on parts that are good or go to the Stealership for them to tell me everyhting is normal...

BTW.... Alternator and Battery were checked out and both passed with flying colors... Alternator was taken to a place that rebuilds them and they said it was like brand new off the shelf with the readings they got, so that I would think eliminates both of them. When the Volts are high it is totally overcharging my battery and he had do drain it down before he did its test...

Anyone???

 

[blueflamed03]

sounds fine. Most will sit at 14.4v running.

 

[merlin1128]

Mine starts out at 14.4 and I found out on the 2005 they added some modules to increase fuel economy where upon start up it will go to 14.4 and hold for 30 seconds. Then upon demand upon certain accessories which were 6 of them, but I only remember 3 from all the reading I did... Headlights, windshield wipers (even on intermitent), and cooling fans will cause a voltage rise.

Here is my problem.... I am getting the 14.4 volt initial reading, but then it climbs up to around 15.2 - 15.3 and will hold their on a 300 mile trip...

If I disconnect the battery and let it sit for say an hour or so, the Tahoe will do exactly what some GM tech wrote it will do... 14.4 to start then upon demand engage the alternator to supply what is needed to keep it in the 13.0 to 13.2 range.....

This is the 3rd time I have had to disconnect the battery to get it to correct itself and then it will be fine for about 3 days, then right back to the 15.2 to 15.3 constant readings.....

Funny thing is all this started when I took it in for the GM Dash Recall and they had to reprogram the computer for the dash....I know electronics are designed if they get an over voltage to shut down... Well my Portable GPS and my ****** Radar do just that.... Cooling fans I noticed turn on for no reason when the engine isnt even close for them to turn on and before anyone asks, yes the AC is of because I know they turn on with the AC turned on......

My guess is bad dash cluster or GM screwed up on the reprogaming the computer... Kinda weird how all this happend after they did the recal and reprogrammed the computer..... Plus with this GPS it has the ECO Route HD that has the OBD connection and I know going by the dash voltage guage it is really high, so I know the reading on the GPS has to be correct.... My Temp Gauge is WAY Off

One more thing.... Fuel Economy is HORRIBLE when the volts are high... The GPS shows your MPG for each trip and when running correct I am getting about 13.5 city.... I took a 1/2 mile trip to pick my son up from school and since volts were high I put in the address to see what I would get.... It showed me at 6.9mpg and this was a straight shot with no stops

I am taking it to the dealerr for them to check because the mechanic already did alternator and battery tests and all were fine... He even said my battery was WAY over charged and had to drain it before he did the test...... He even sent it to a shop that rebuilds alternators because they have more advanced diagnostic tools then he does and they said the alternator was like brand new off the shelf and regulator shows it should be cutting it off at 14.4.... They said it has to be a computer problem or a relay inline with the computer keeping it in charge mode...

I am betting on the bad dash cluster or programeed wrong....

I will post what the dealership says after I take it in... I hope they dont give me some BS...

 

[merlin1128]

Problem all corrected.... Long story short went on another 300 mile trip and their was a Chevrolet Dealership in Town... The ride up their Votage was in the High 15's according to the digital thing attatched to the OBD connector...I was burning out lightbulbs and since the problem started I was up to 5 and during testing it they burned one out.

The Dealership found that the Battery Control Module failed causing it to not stop the alternator from charging and was over charging my battery.... On the 2005 model from what I was told is when they put one on the negative battery cable and that is where it is located with TONS of wires coming out of it.... Basically from what they told me it is intergrated with tons of stuff on the Tahoe....

Makes sense why my Fuel Mileage was GARBAGE TOO.... Who knows what else it was doing, but all is good now that they changed it. From what I read this is not a part you can change yourself and the dealer has to do it because the computer needs to be programed for it... If that is true I really do not know.... But... Leave it to GM to make you bring your Tahoe into them for a simple bolt on part that they need to program.....

Heres a great link I found that explains it all....

http://www.carkb.com/Uwe/Forum.aspx/chevrolet-truck/3574/Tahoe-2004-2005-differences

 

[dwmmatt23]

Ok now that you posted this it got me thinking, my voltage indicator on my cluster is constantly up in the 15 range, the 1 1/2 year that ive owned it its been that way never higher never lower. I took it as maybe because it was the Z71 with towing package and larger alternator it would be a little higher, can anyone confirm or deny this? just curious cause I get CRAP mileage, I mean Ive gotten 10mpg since I got it and have done just about everything known to try and fix it and now I get maybe 11mpg. Now Im wondering if this is not normal

 

[Physh1]

Test off the battery, obdII, or off the alt. Don't expect super accurate voltage reading from the gauges. My gauge 'reads' 13.5, off batt & alt is 14.4

 

[Rivieraracing]

Thanks for the update Merlin1128, that's good info to know! Hope it stays working for you!!

 

[dmk]

My 2008 Tahoe LTZ just started with the voltage staying constant at 15.2-15.4 volts. I took it into the dealer yesterday, and they replaced all the battery cables per a TSB but it did not correct the problem. Then they reprogrammed the Body Control Module and found that it was always reporting that the battery was dead. I left the vehicle overnight, and today they consulted with Tech and were advised to replace the BCM. I received a call to let me know that the problem is fixed, and I can pick up my Tahoe after they wash it. I will let you know if the problem is still there, but the Service Mgr assured me that they have it corrected. I have 60K miles, and thankfully purchased the GMPP, so it is all being fixed at no charge.

 

[WildBill]

Im glad the op found the issue.

Just a note to those with electrical issues...an item USING power cant draw more VOLTAGE, it can draw more CURRENT only. The alternator responds by supplying more current, if it cant keep up, the voltage DROPS. So a higher voltage would trace to the charging system some how.