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01-22-2022, 06:36 PM | #1 |
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Vacuum erratic when electric fans turn on
A while back ago while I was adjusting my mixture screws on my quadrajet using a vacuum gauge I noticed that whenever my electric fan turned on I noticed that the vacuum would drop slightly and become less stable. Meaning that the needle would jump up and down. Is that normal? It doesn’t seem like it should be doing that. My only thought is that my fans are somehow effecting the power going to my distributor.
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01-22-2022, 07:09 PM | #2 |
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Re: Vacuum erratic when electric fans turn on
Do you know where your alternator sensing wire is attached? Is it a 3 wire?
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01-22-2022, 07:20 PM | #3 |
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Re: Vacuum erratic when electric fans turn on
No I don’t. I don’t even know what that is. It is a single wire internally regulated single wire alternator.
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01-22-2022, 11:47 PM | #4 |
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Re: Vacuum erratic when electric fans turn on
It sounds like as though that is not the way my vacuum should react when my fans turn on. I am sorry if I seemed harsh when responding to the previous response. I appreciate any help I can get.
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01-23-2022, 12:33 AM | #5 |
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Re: Vacuum erratic when electric fans turn on
Does this happen with the air cleaner on or off the Carb?
If you have the air cleaner off, the extra air flow could cause a Difference, Do you have 12 volts running to the distributor?
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01-23-2022, 01:46 AM | #6 |
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Re: Vacuum erratic when electric fans turn on
The air cleaner is on. I will check what the volts are at the distributor
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01-23-2022, 01:04 PM | #7 |
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Re: Vacuum erratic when electric fans turn on
The extra load on the alt. is slowing down the engine enough to efect the vacuum. Try increasing the idle speed a little.
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01-23-2022, 06:10 PM | #8 |
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Re: Vacuum erratic when electric fans turn on
So I am getting 12 volts at the distributor with the fan off. It drops to 11 when the fan turns on.
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01-23-2022, 11:17 PM | #9 |
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Re: Vacuum erratic when electric fans turn on
Is the cab grounded to the frame?
And also, Does the Front radiator support (Have a Great) ground to the frame?
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01-23-2022, 11:49 PM | #10 |
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Re: Vacuum erratic when electric fans turn on
Do you have a relay in the fan circuit. If not it is preferred to have one.
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01-24-2022, 12:02 AM | #11 |
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Re: Vacuum erratic when electric fans turn on
The cab is grounded to the frame. But other than the bolts the radiator support is not. The radiator is aluminum and so is the shroud that the fan is bolted to and the fan is plastic. What is the best way to ground it?
Last edited by forestb; 01-24-2022 at 12:35 AM. |
01-24-2022, 12:02 AM | #12 |
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Re: Vacuum erratic when electric fans turn on
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01-24-2022, 12:32 AM | #13 |
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Re: Vacuum erratic when electric fans turn on
I looked though my old receipts and the harness that came with the fan does indeed have a relay.
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01-24-2022, 12:48 AM | #14 |
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Re: Vacuum erratic when electric fans turn on
I think that my thermostat for the fan completes the ground. I am wondering if grounding the radiator support will interfere with that.
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01-24-2022, 08:39 AM | #15 |
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Re: Vacuum erratic when electric fans turn on
The fan must draw some juice if it drops voltage to 11 volts. The alternator isn't keeping up.
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01-24-2022, 02:07 PM | #16 |
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Re: Vacuum erratic when electric fans turn on
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01-24-2022, 02:08 PM | #17 |
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Re: Vacuum erratic when electric fans turn on
Also do you think that this could cause a random stutter during acceleration?
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01-24-2022, 02:15 PM | #18 |
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Re: Vacuum erratic when electric fans turn on
Engine running it should read 13.5 volts up to 14.5. Key on engine off 12.5
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01-24-2022, 02:32 PM | #19 |
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Re: Vacuum erratic when electric fans turn on
I would ensure there were grounds to everything including the alternator to motor and motor to battery, If you radiator support has anything ground to it then by all means that needs a clean ground, including frame, body etc, etc. You can't have power if you don't have grounds.
As far as your alternator please read this article on alternators - http://www.madelectrical.com/electri...hreewire.shtml They work!
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01-24-2022, 02:56 PM | #20 |
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Re: Vacuum erratic when electric fans turn on
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01-24-2022, 03:01 PM | #21 |
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Re: Vacuum erratic when electric fans turn on
I have a frame to engine ground and on that same bolt a engine to frame ground. I also have a engine to frame and a cab to frame ground but no core support to frame ground. I also have a alternator to valve cover bolt ground.
Last edited by forestb; 01-24-2022 at 03:11 PM. |
01-24-2022, 03:03 PM | #22 | |
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Re: Vacuum erratic when electric fans turn on
Quote:
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01-24-2022, 03:57 PM | #23 | |
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Re: Vacuum erratic when electric fans turn on
Quote:
I'd call the manufacturer or look up the part number to make sure if it were me.
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01-24-2022, 04:28 PM | #24 | |
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Re: Vacuum erratic when electric fans turn on
Quote:
Last edited by forestb; 01-24-2022 at 04:38 PM. |
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01-24-2022, 04:46 PM | #25 | |
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Re: Vacuum erratic when electric fans turn on
Quote:
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