Should I Hook Up My AC Manifold Gauges at Every Service Call?

Should You Hook Up Your Manifold Gauges Every Time?

Maintaining the Integrity of Your Sacramento Valley AC System

As a technician starting out in this field, I was told by the company trainer to hook up the hoses to my manifold gauges every time I’m out on an AC service call.  Much like a doctor who wears a stethoscope around his neck, hooking my gauges up meant we were the professionals; and when I bring the customer out to the AC to discuss recommendations or repairs, they would see I was the one with all the knowledge.  Was my trainer onto something, or was this just another effort to blow smoke up the customers rear and make him fall for that company’s high-pressure antics?

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Manifold Gauges: How They Work

Every residential air conditioner has a service valve used by technicians to connect to and read the pressures of the system’s refrigerant. Those service valves have a Schrader core (That’s Schrader Core) that gets depressed when the technician’s manifold hoses attach to the service valve.  It’s just like a valve stem on your bicycle tire.

When the core gets pressed in, the refrigerant is allowed into the technician’s manifold so the pressure can be read on the gauges.  It takes an experienced technician to interpret those readings to accurately determine what’s going on with the refrigerant pressures in the system.  Simply put, we can see the temperature of the evaporator coil, the condenser coil, and can determine the superheat and subcooling levels for that system.

Getting an Accurate Manifold Gauge Assessment

But do technicians need to hook up every time they go out on preventative maintenance or a service call?  Does it mean we didn’t give a full and comprehensive diagnostic if we don’t?  No!  Most technicians will walk up to a system and assess how the system is running by doing a couple of things.  First, have you asked the customer how their system is running?  If not, that’s valuable information to get.  If the system has been running great according to the customer, there may not be any reason to hook up the gauges.

Steps for Technicians

Let’s say you’ve asked the customer how the system has been performing.  They report that the system’s been running fine.  They just wanted to call you out for a pre-season tune-up, like the ones we offer at Fox Family for just $75.  Have you checked the temperature split to see if the system is blowing nice cold air?  That would be more input that should sway a technician from hooking up their gauges.

I know it’s a little cliché but checking the temperature of the suction line can further indicate that you wouldn’t need to hook up your gauges to the AC system.  The liquid line should be a few degrees warmer than the outside temperature, too.  So, making some initial checks like this can make someone comfortable about not hooking up their gauges to the system.

Why don’t I think you should hook up your gauges so much?  Hooking up your gauges can do several things to actually harm the performance of the system over the long run.  Maybe not today, but the overall lifespan of the system can be affected.

Contamination

I feel that hooking up gauges from one system to the next contaminates the next system you hook up to.  Taking a little bit of refrigerant from one system, going to the other side of town and putting your gauges on that system has now introduced a trace of contaminants that system has never seen before.  Moisture and air from one system can easily be transferred to another system.

This is definitely true if your no loss fittings or ball valve fittings on your hoses retain the R22 freon in one system and then get hooked up to that one on the other side of town that is an R410a system.   A technician doing this will literally create a new mixture, a new refrigerant even.  Done enough times, it will throw off the system readings enough that not even the most experienced techs can get the true pressures inside that system.  Eventually, a future technician will recommend removing all the refrigerant and starting over with a new manufacturer’s charge of refrigerant.

Avoiding Burns

Another reason is to reduce the chances of exposing yourself to refrigerant burns.  In the unlikely event that you find a burr in the threading of the service valve and get it stuck it could create a situation where the refrigerant starts shooting out of the hoses.  Some techs will persist in trying to get the hose off and burn themselves.  The risk is small, but but tell that to the techs who have ended up with huge blisters on their hands trying to play hero and losing time off work.  Further impacting their paychecks and livelihood is a serious consideration.

Unintended Loosening

My last reason to think twice about hooking up gauges to every AC system is about the Schrader core.  It can be loosened, creating a tiny leak.  The Schrader core is threaded into the service valve.  And while you’re screwing the new core into the valve which way are you tightening it?  Righty tighty.  Lefty loosey.  Taking off your hoses in the normal counterclockwise direction mimics the same direction it takes to unscrew the Schrader core.

Case in Point

Several times this year I’ve gone out on a service call for no cooling.  The client reports that the system only blows room temperature air.  They’ve have been having maintenance done by a local company every spring and fall. Upon inspection, I saw there was no temp split from the registers.  And the suction line at the AC was warm to the touch.  I unscrewed the service valve cap to attach my hoses.  There, I saw some liquid refrigerant spewing out of where the valve core sits.  I think I’ve found the problem.

Put another way, I’ll quote a recent story in ACHR News:

“There is no reason to ever put gauges on an air conditioning or refrigeration system after the initial installation unless a problem with the mechanical refrigeration circuit is suspected.  Using a psychrometric chart, digital thermometer, digital humidity stick, and an accurate method to calculate airflow can replace having to apply your manifold gauges anytime.”

Increasing Equipment Life

Remember, these systems should contain only virgin refrigerant.  Spending less time putting on and taking off our refrigerant hoses saves more than time.  It increases equipment life, maintains performance, and reduces refrigerant emissions into the atmosphere.

Remember, I was told by the company trainer to hook up my manifold gauges on every AC service call.  He said it would make me look like the doctor who wears a stethoscope around his neck.  Customers supposedly expect to see those hoses hooked up, and if they weren’t, they might think something wasn’t right.  The trainer wasn’t worried about the integrity of the customer’s AC system.  And certainly not the integrity of his company’s high-pressure sales antics.

Your Turn

As always, I appreciate you all for reading our blog posts here at Fox Family in Sacramento.  I would love to hear your comments as technicians out in the field.  How does your company practice service and maintenance calls and hooking up your gauges every time you get called out?

Thanks so much for stopping by and we’ll see you on the next blog topic!

Don’t miss our video on this topic:

Should You Hook Up Your Manifold Gauges Every Time?

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