Same voltage at idle or under acceleration - Ford Powerstroke Diesel Forum
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Old 11-11-2013, 12:00 PM
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Same voltage at idle or under acceleration

Hello to everyone.
This is a 96 7.3, runs on diesel and wvo, fuel bowl erased and electric pump mod.
I replace the alternator 1500 miles ago and I just notice the voltage on the batteries acting weird.

Basically I start the engine and it takes around 30 seconds to jump from low voltage to normal. This wasnt like that, it normally jumps immediately after start, or 5-10 seconds...Then it remains the same at idle or under acceleration... It wasnt like that 1500 miles ago...

I tested after I replaced the alternator and it was working what I assume was normal... more voltage under acceleration, but now is different...

I tested this morning and this was the result
1. off: 12.3 volts
2. on 11.6
3 after 30 seconds. at idle 14.3
4. under acceleration 14.3
5. after 2 hours driving 14.3

The other thing I noticed is that the idle is not the same, is kind of irregular, and this happens when the clutch of the A/C starts spinning. My A/C is not working by the way...

What can it be?
can this be bad for the truck? Should I worry about ???

thanks for reading
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Old 11-12-2013, 09:16 AM
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Low voltage after startup is normal. That's the glow plugs cycling, drawing a LOT of alternator power. It can go 30 seconds up to two minutes. But 14.3 is on the low side. It should be about 14.5. Could be alternator or batteries. Have you _load_ tested the batteries?

The A/C clutch will only spin when the HVAC selector is in the A/C, MAX A/C or windshield defrost (far right) position. If you're using the windshield defrost, and the A/C is not working, you can disable the compressor by disconnecting the electrical connector.
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Old 11-12-2013, 01:14 PM
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thanks madpogue.
I did a load test and it was ok, it when down for a second and after that came back to 14.3..
Im going to check if the ac clutch is working with everything in off...
Any ideas why when i accelerate, the voltage doesnt go any further?
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Old 11-12-2013, 08:56 PM
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Your voltage is fine. The concern is why the truck wasn't working properly 1500 miles ago. That could be from temperature change or something on the glow plug circuit that just fixed itself. I suspect it was the GPR, it could have been stuck and just fixed itself.

Your idle issue could be related to the AC compressor. Try unplugging the compressor, IIRC it's a 2 wire plug. Also, just try watching the compressor clutch when the idle is acting up, see if it's spinning.
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Old 11-16-2013, 08:29 AM
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Quote:
Originally Posted by JSchuricht View Post
Your voltage is fine. The concern is why the truck wasn't working properly 1500 miles ago. That could be from temperature change or something on the glow plug circuit that just fixed itself. I suspect it was the GPR, it could have been stuck and just fixed itself.

Your idle issue could be related to the AC compressor. Try unplugging the compressor, IIRC it's a 2 wire plug. Also, just try watching the compressor clutch when the idle is acting up, see if it's spinning.
Thanks for the reply

GPR I replaced a few months ago...
Im checking the thing now and the idle is better when the Ac clutch is not engage so Im going to fix it...
The voltage came back to normal the other day, I mean normal is different volatge at idle and under acceleration, so Im going to have an eye on that thing, somehow I think is related to the A/C..

Thanks guys for the input
Best
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Old 11-16-2013, 10:31 AM
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In what position is the HVAC control?
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Old 11-16-2013, 03:08 PM
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Quote:
Originally Posted by madpogue View Post
In what position is the HVAC control?
You mean the A/C control?
I tried in off and vent...
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Old 11-16-2013, 10:26 PM
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Yes, HVAC == Heating, Ventilation and Air Conditioning. In the OFF and VENT positions, the A/C compressor clutch should NOT be engaged. There may be an underlying electrical issue.
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Old 11-17-2013, 09:18 AM
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Quote:
Originally Posted by madpogue View Post
Yes, HVAC == Heating, Ventilation and Air Conditioning. In the OFF and VENT positions, the A/C compressor clutch should NOT be engaged. There may be an underlying electrical issue.
When is in off position, it doesnt engage, so Its working good... just noticed the idle slows down a bit when is on...

Now I have a bigger issue so Im going to focus on that one..
this is my problem now if you have any idea

Engine deep sound, what can it be? with video

Thanks
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