Auto A/C Diagnosis, Pressure Gauge Readings and Temperature Tips & Tricks - Be sure you take pressure gauge readings properly!

Auto air conditioning - Auto A/C troubleshooting, service, repair, recharge and retrofit manuals for all A/C technicians... from the apprentice to the pro!

Sponsor or
advertise at our
A/C Sites

Auto A/C troubleshooting, recharge, repair and service information
...for everybody from the apprentice to the professional!

Auto A/C
and repair Manuals


Auto A/C Forum

Auto A/C Parts

A/C Manuals

A/CE™ Manuals

Auto & A/C Parts at Auction

Video Help

Auto air conditioning service products, repair and troubleshooting manuals are available at the COOL ZONE! Secure on-line transactions powered by WorldPay!

Auto A/C parts warehouse

SECURE On-Line Ordering

Secure online shopping for all of your auto air conditioning service products and repair manuals at the COOL ZONE! Secure purchases powered by WorldPay!

Add us to your favorites!
Make autoACsystems your homepage!
Tell a friend about autoACsystems
Would you
share you comments with us?

What auto A/C help can we get for you?

Auto A/C?
A/CE Manuals for auto A/C Diagnosis
Auto A/C FAQ's
Find an A/C Shop
Auto A/C eZine
A/C Tubemaster Professional Auto A/C Hose Repair Solutions

Other A/C Training Solutions & Help

Training Solutions for Corporate Accounts
Solutions for Instructors
Become an autoACsystems affiliate
Sponsoring / Advertising

Have you heard what our Auto A/C eBook customers are saying?

This was probably one of the best books on recharging air conditioning that I have seen...
The e-manuals are absolutely terrific and a great value...
The information was exactly what I needed...
I think these e-books are an outstanding value...
Read more about what customers are saying

Additional help for A/C
Service Shops &
Web Sites

Get Your Shop a Web Site now!
Are you listed in our A/C Service Directory?

Other A/C Training Solutions & Help

Auto A/C Links
Link to autoACsystems
Site Map
See What COOL PROFIT$ Has to say

Your best source for complete troubleshooting and diagnosis information on auto A/C systems. Our information provides proper repair, recharge, service and maintenance procedures for all automotive air conditioning systems. Regardless if you have a current CCOT (cycling clutch orifice tube) system or an expansion valve and POA valve system, we've got the information you need. From step-by-step help on retrofitting and recharging to complete A/C compressor or component replacement, our A/C manuals provide you a quick and easy methods that have been proven helpful to everybody from the apprentice to the professional.

Does your A/C parts business have enough sales?
The answer should be that there's never enough! That's why you should contact us now to understand the wide variety of solutions and programs we have available! Include your products in our eBooks! Get listed at the COOL ZONE! Plus a whole lot more opportunities!
Contact us now!

Auto A/C Technical Tips and Tricks the pros use every day!
Auto A/C Pressure Gauge Readings
Is there a difference between taking
gauge readings with the hood up or down?

Get all the news, updates & special offers from your on-line A/C Connection! Subscribe to our e-mail newsletter today!

Review past issues of our auto A/C newsletter


Manifold Pressure Gauges Readings with the Hood Up or Down?
When you're diagnosing auto A/C system, there really is a difference!:

When you're performance testing an auto A/C system, should you take pressure gauge readings and duct outlet temperatures with the hood up or down? When you think about it for a minute, it may appear pretty difficult (not to mention tricky) to get pressure gauge readings when the hood is down, but there is a good reason why you may want to.

Understand that the air inlet for the A/C system is right at the base of the windshield. Typically, the air inlet will be covered with a screen to prevent debris and other foreign material from falling in. You should also notice that between the air inlet and the engine compartment, there is a long rubber strip that runs the entire length of the firewall. That's a really important piece of rubber when it comes to keeping you cool!

What's a 'hood seal'?
That long strip of rubber on top of the firewall is the hood seal. With the hood open, you should be able to see where that rubber contacts the hood from one side to the other. When the hood on the vehicle is closed, that rubber strip or hood seal prevents hot under hood air from being drawn into the air inlet of your car's air conditioning system. When the hood is up, instead of drawing outside ambient air temperature of 80° F or 90° F into the air inlet, you're pulling hot under hood air that could be 200° F or more!

What's it really mean?
For the most part, when diagnosing and testing auto A/C systems, you should be all right doing that with the hood up. You should be able to take pressure gauge readings and perform your tests without problem. However, understand that in cases where there is poor air circulation (typically inside service shops) and the vehicle is being operated for extended periods of time, there will be a continued increase in A/C pressures and duct outlet temperatures.

In order to check or verify the A/C system, lower the hood. Use caution not to get the manifold gauge hoses caught or damaged, but with the hood lowered, you will start to see an improvement in the gauge readings.

On sever applications or problem jobs, a good tech tip is to set up the gauges in a way that you can actually close the hood. That will provide you the most accurate pressure gauge readings and duct outlet temperatures for the A/C system. There is a difference and the pros will use this trick to assure themselves that the A/C is really working properly.

Here's a look at how the hood seal works to help prevent hot under hood air from entering the auto A/C system's air inlet:

When you're taking pressure gauge readings and duct outlet temperatures, it's a good idea to consider doing that with the hood lowered. That way, you will prevent hot under hood air from entering the A/C air inlet and you will get a more accurate pressure gauge and temperature reading!

This particular illustration does not show the hood. However, the hood seal is highlighted in 'red' and marked. That hood seal is a strip of rubber that seals against the hood when it's closed. That rubber prevents hot under hood air from entering the A/C system's air inlet, typically located at the base of the windshield. A good idea is to clean that hood seal and spay it with a silicone spay to help keep it soft and maintain it's seal!

Shop for Manifold gauges, couplers &
hose sets now at the
COOL ZONE™ On-line
A/C Parts & Tools Warehouse

Manifold Gauge Sets for every budget!

Quick Couplers for charging R-134a Systems. We've also got kits to convert your R-12 Gauge Sets!

Manifold pressure gauge hose sets in a variety of lengths!


Quick Couplers
& Kits to
convert your
R-12 Gauges


See all of the Auto A/C
Troubleshooting & Diagnosis
available at

Don't forget... you will really need
Your Auto A/C Connection!™ :
This is an absolute must! The Auto A/C Connection!™ is a complete and perpetual auto A/C Service and Parts Source Guide. If you service auto A/C, then you have to have this. It includes constantly updated information that you use every day! Complete detail like refrigerant capacities, A/C compressor oil details, clutch air gap details and more! You just won't believe what's included... and best of all, it's free!

Auto A/C Manuals  - We wrote the book on auto A/C service, repair and recharging! Get all the details now!

Review other Auto A/C Tips and Tricks
Archived from Weekly Updated Tips and Tricks!

We've maintained all of the weekly auto A/C service and repair tips and tricks in our archive so that you can browse and review them at your leisure. .

Questions? Discuss this tip or others at
the COOL ZONE™ Auto A/C Forum

Get all the right answers from the auto A/C professionals!

There is only one auto A/C help forum where the professional provide you
all the right answers... all the time! Be sure you register now!
Visit the Auto A/C Help Forum at the COOL ZONE Now!

Auto air conditioning service products, repair and troubleshooting manuals are available at the COOL ZONE! Secure on-line transactions powered by WorldPay!

Keepin' Cool - Your best automotive air conditioning e-zine with updated information on auto A/C parts and general service information. All available from autoACsystems and the COOL ZONE! Your on-line A/C Connection! Polymax Refrigerant Oil - Replaces PAG, Ester and Mineral oil - Approved for use in all Auto A/C systems and with all refrigerants too! R-134a! R-12! Hydrocarbons and blends! HC's! R-12a and more! Braze Perfect! Simply the world's easiest aluminum brazing solution! Repair A/C hoses and lines with a standard propane torch!

© Copyright 2005 -2006- - All Rights Reserved
Auto A/C Help and Discussion Board at the COOL ZONE™ © 2004-2005
Buy & Sell Auto A/C Parts, Tools and Equipment at the™ - © 2005 - All Rights Reserved
Powered by autoACsystems web servers - | Privacy Policy | Contact | About