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car vibrates/hums
#1
In another thread I have been dealing with some fuel system issues on my '73 Mach1 351C, which you guys have been very helpful with.  Thank you.

I've gotten everything fuel related back together, but now there is another issue that wasn't there a month ago when I had been trying to start the car.

The battery is charged.  Over the last few days. the car has been doing the following:

- not cranking
- when I turn the key, clicking as if the battery was low
- when I turn the key, the car hums/vibrates that I can feel through the seat
- when I open the door the car hums/vibrates until I close it

I have replaced the ancient battery cables and starter solenoid but the car still does the above.

I've been working on cars a long time and have never seen or even heard of this happening, especially the humming/vibrating

Any ideas what's going on?
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#2
(04-23-2018, 09:03 PM)scottyrocks Wrote: In another thread I have been dealing with some fuel system issues on my '73 Mach1 351C, which you guys have been very helpful with.  Thank you.

I've gotten everything fuel related back together, but now there is another issue that wasn't there a month ago when I had been trying to start the car.

The battery is charged.  Over the last few days. the car has been doing the following:

- not cranking
- when I turn the key, clicking as if the battery was low
- when I turn the key, the car hums/vibrates that I can feel through the seat
- when I open the door the car hums/vibrates until I close it

I have replaced the ancient battery cables and starter solenoid but the car still does the above.

I've been working on cars a long time and  have never seen or even heard of this happening, especially the humming/vibrating

Any ideas what's going on?

Possibly a dying seat buzzer?
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#3
Sounds like a starter solenoid issue. The vib is a relay going on/off very fast.

73 modified Grandé 351C. Almost done. 
71 429CJ. In progress
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#4
dude you're almost there all you need is to get it to 88 mph and you're set...................
on a serious note, the hum is a failing electrical component that you need to hunt down as a priority just to avoid a nice 71-73 car-b-q
if the hun is identical on attempted start to when you have the door open ask midlife if he can give you a top 5 on things that it could be with two different circuits doing it hes the man to throw out the common components of both off the top of his head, david or don may too but midlife snorts 12vdc on the reg Smile
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#5
(04-25-2018, 04:16 AM)libram Wrote: dude you're almost there all you need is to get it to 88 mph and you're set...................
on a serious note, the hum is a failing electrical component that you need to hunt down as a priority just to avoid a nice 71-73 car-b-q
if the hun is identical on attempted start to when you have the door open ask midlife if he can give you a top 5 on things that it could be with two different circuits doing it hes the man to throw out the common components of both off the top of his head, david or don may too but midlife snorts 12vdc on the reg Smile

"Snort".
I have no idea other than if it is a high pitch hum it is likely an electrical vibration due to a bad relay somewhere.  If it is a lower frequency hum, it is likely mechanical.  Does it happen with the engine off?

Let me check your shorts!
http://midlifeharness.com

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#6
Are we talking maybe about electric seat back release vibrating? That would happen with the door opens, but the key switch shouldn't have nothing to do with that.
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#7
When you open the door does it make any difference if the key is in the ignition or not? If not, likely to be the seat back latch release relay or latch release solenoids. They all have contacts in them that could be arcing or worn out. The solenoids are probably what you are hearing and feeling.

It could also be a weak connection that loads the circuit when the solenoids kick in, reducing the voltage and causing the relay to drop out, re-energize, drop out....



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#8
To answer all the diagnostic questions:

It happens with the engine off. The car does not start.

It is a low frequency hum that sounds and feels like it's throughout the car.

I have replaced the solenoid and the same thing occurs.

The key was in the ignition when I opened the door and the hum occurs. I didn't think to remove the key.

I didn't know there was anything in the seat that could cause this. The seats in this car are not electric. Yes, sometimes the seat feels like it's clicking. I will get in there and find the component.
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#9
(04-25-2018, 05:56 PM)scottyrocks Wrote: To answer all the diagnostic questions:

It happens with the engine off.  The car does not start.

It is a low frequency hum that sounds and feels like it's throughout the car.

I have replaced the solenoid and the same thing occurs.

The key was in the ignition when I opened the door and the hum occurs.  I didn't think to remove the key.

I didn't know there was anything in the seat that could cause this.  The seats in this car are not electric.  Yes, sometimes the seat feels like it's clicking.  I will get in there and find the component.

Not electric in that it is not electrically adjustable.  But there may be an electric seat back release.  Mine was working when I got the car and now that I think about it....I haven't heard that sound of the release in a while!  Where on Long Island do you live?  If mine is still working you may be able to compare the sound and see if that is what you are hearing and look at the wiring.
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#10
By any chance do you have an electric fuel pump?

Let me check your shorts!
http://midlifeharness.com

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