vent fan causing rough idle
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Freshman User
Joined: May 2009
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From: Lafayette La
vent fan causing rough idle
When I switch the vent fan on the Temp gauge reads double the normal temp. This occurs with the ac on or off. I mean if I'm just using the vent with the ac off. My tach doesn't work either and when the fan is switched on the engine idles rough, any ideas?
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Thread Starter
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Freshman User
Joined: May 2009
Posts: 36
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From: Lafayette La
yes
It wouldn't switch speeds when I bought the truck but I replaced the transistor that controls the speed with one off the parts truck. Funny though, if I flip the switch to medium it changes. Maybe the controller or the alternator. This all started after I replaced the battery ground.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Hmmm, you might want to check the condition of the blower motor itself. If the armature has gummed up over the years or there is excess drag on it due to misalignment or crap caught in the squirrel cage (fan blade) it could be drawing more power than it should by virtue of the additional drag on the blower motor itself. You should be able (with the blower motor/fan assembly removed) spin the motor by hand and have it spin freely and easily. While you are checking things, make certain you have a good strong negative (ground) connection to it as well.
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Freshman User
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From: Lafayette La
I actually started to have this problem after I replaced the ground. When the AC is switched on the Temp gauge goes from normal to twice as hot, if I turn it off it goes right back to normal, really weird.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
That sounds like a poor engine block ground. The compressor clutch is grounded as well, and when the circuit is energized the ground on the clutch is probably in better condition than the ground on the block. This would explain the poor performance as well. Poor negative (ground) to the block and heads doesn't allow the spark plugs to "ground out" like they are supposed to to achieve a good strong spark.
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Freshman User
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From: Lafayette La
Ground
So I'll take the ground off at the block and clean it real well and replace the little solenoid at the battery and see what happens. I think there is something definitely electrical here, the flashers sometimes click very low or don't flash at all and the head light warning buzzer doesn't sound anymore or that weird radio buzzer when you pull the ignition key out. Any way to test the ground with a multimeter?
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Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Check resistance (ohms). The difficulty is that in order to effectively check you must check the resistance between the negative battery post and the negative wire running to the devices that are having difficulty. You might check that your have a strong connection to the frame and block to begin with. Always check resistance on the negative between the negative battery post and the point at which you suspect a problem. If your meter has an audible resistance buzz or beep that's the easiest way to check. If for some reason, you don't get an audible response from your meter, its likely there is a problem. Otherwise an iron vane meter should peg the needle and a digital should read near 0.00 ohms if it has no audible alarm.
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Freshman User
Joined: May 2009
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From: Lafayette La
new problem
Ok, so I checked the engine to battery ground it looks good to me but im no expert. The rough idle from the fan was indeed a vacuum leak that has been repaired. Now I have ripped out all the emissions and cut all the wires from the pump and removed it which blew the emission control fuse and caused the tach to go out. I replaced the fuse with a 25amp instead of a 15amp and now when I turn the AC on the tach reads 2000 at idle and the temp gauge reads twice as hot and the blinkers blink twice as fast and also a scary looking thing are sparks coming from the dip stick if I try to check the transmission oil. Does this sound like a ground problem or a short in the AC or a short in the Emissions? And how do you recommend troubleshooting this problem?
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