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2006 gmc envoy_denali
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53 Posts
Discussion Starter #1
Howdy,
I changed my fan clutch in 2018 when it failed and I used a cheaper clutch replacement that since then just failed so I have an ACDelco one on the way.
I did want to ask do you think a failing fan clutch could cause random voltage drops ?

For a few weeks I noticed that if I was at idle for a while at a light or in a parking lot randomly the voltage gauge would drop to the big line between 14 and 9 I would say right at 12. My ODB2 scanner live diagnostics says I was at 13.4-6 depending so it seems like bat and alternator at hot idle is functional. I did test it with a load tester and it did read in the low normal range.
Just curious like I said if the bad fan clutch going out could have caused the random voltage drop which caused idle to go down a little.
Thanks!
 

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2002 chevy trailblazer_lt
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442 Posts
bad fan clutch going out could have caused the random voltage drop which caused idle to go down a little.
Far more likely for a rpm drop to cause a voltage drop. The fan clutch uses very little electrical power, not enough to even be seen on a battery voltage reading I would believe.
 

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2004 chevy trailblazer_lt
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339 Posts
The alternator output is controlled by the PCM. When demand for current is "low", the voltage will drop and since the volt meter on the instrument cluster is not calibrated, it can appear that the voltage drops well below 12 volts.

This drove me nuts for the first year I owned my TrailBlazer and I had it into the dealer where I purchased it several times for this. Finally the shop foreman came out and explained to me that this is normal operation for these alternators and instrument cluster volt meters.
 
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