Not typical A/C system in defrost mode
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Joined: May 2006
Posts: 334
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From: Jupiter, Florida
Car: 92 Z-28
Engine: 305 TPI
Transmission: THM700R4
Axle/Gears: 2.73
Not typical A/C system in defrost mode
Ok, I think I have read just about all the posts for this problem and I cannot figure out what the problem is. Vacuum ball is mounted and functioning. 2 years ago, I replaced the vacuum hose that runs from the check valve at the intake manifold to the vacuum tank and the vacuum selector valve (the disc that changes where the vacuum is routed behind the control panel). All the hoses are connected in the engine bay where they are supposed to. I do not hear any vacuum leaks at the control panel or in the engine bay (although even with a hose to listen for leaks, the noise from the engine is loud.)
I do have a FSM and that has helped me to understand more about the system. The only checks they request you do is “check for faulty components.” Before I start taking pieces off and checking, I am wondering if anyone has any suggestions.
I know I have to be losing vacuum somewhere (I could not hear a leak) or the vacuum that I am getting is not enough to power the system. Does anyone know how much vacuum I am supposed to be getting off the intake to power the system?
I do have a FSM and that has helped me to understand more about the system. The only checks they request you do is “check for faulty components.” Before I start taking pieces off and checking, I am wondering if anyone has any suggestions.
I know I have to be losing vacuum somewhere (I could not hear a leak) or the vacuum that I am getting is not enough to power the system. Does anyone know how much vacuum I am supposed to be getting off the intake to power the system?
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Joined: Jan 2000
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From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: Not typical A/C system in defrost mode
Test it with a hand vacuum pump with the engine off.
Thread Starter
Member
Joined: May 2006
Posts: 334
Likes: 1
From: Jupiter, Florida
Car: 92 Z-28
Engine: 305 TPI
Transmission: THM700R4
Axle/Gears: 2.73
Re: Not typical A/C system in defrost mode
PepBoys has a vacuum pump for about $35.00. That would allow me to hear better any leaks not having to run the motor for sure but will it be able to test how much vacuum is coming off the intake?
Last edited by hot92RS; Nov 17, 2010 at 09:35 AM. Reason: more info
Moderator
Joined: Jan 2000
Posts: 20,981
Likes: 11
From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: Not typical A/C system in defrost mode
The amount of vacuum in the intake is "lots". It's not a variable here.
Thread Starter
Member
Joined: May 2006
Posts: 334
Likes: 1
From: Jupiter, Florida
Car: 92 Z-28
Engine: 305 TPI
Transmission: THM700R4
Axle/Gears: 2.73
Re: Not typical A/C system in defrost mode
How do I make sure that I have the proper vacuum for the lines that run the HVAC system controls?
Moderator
Joined: Jan 2000
Posts: 20,981
Likes: 11
From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: Not typical A/C system in defrost mode
I'm not sure what you mean. If the engine runs, it produces enough vacuum.
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