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Should I Hook Up My AC Manifold Gauges Every Time On An AC Service Call?

Should I Hook Up My AC Manifold Gauges Every Time On An AC Service Call?

As an HVAC technician starting in this field, we were told by the company trainer or professionals to hook the hoses up to our manifold gauges every time we’re out on an AC call.
Much like a doctor who wears a stethoscope around his neck, hooking up our gauges meant we were the professionals.

And when we bring the customer out to the AC to discuss recommendations or repairs, they would see we were the one with all the knowledge.
Was our trainer on to something, or was this just another effort to blow smoke up the customers’ rear and make them fall for that company’s high-pressure antics?
Every residential air conditioner has a service valve that technicians hook their gauges up to, in order to read the pressures of the refrigerant inside the system.
Those service valves have a Schrader core that gets depressed when the technician’s manifold hoses attach to the service valve. It’s a lot like a valve 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. And it takes an experienced technician to interpret those readings to accurately determine what is going on with the refrigerant pressures in the system.
We’re not going to get too far into it, but we can see the temperature of the evaporator coil, the condenser coil, as well as determine the superheat and subcooling levels for that system.
But do technicians need to hook up every time they go out on preventive maintenance or a service call? Does it mean we didn’t give a fully 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.
So, you’ve asked the customer how the system has been performing, and they said the system has been running fine. They just wanted to call you out for a pre-season tune-up, like the ones we offer at Red Deer Heating and AC.
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.
We 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 these can make someone comfortable about not hooking up their gauges to the system.
Why don’t we think you should hook up your gauges so much?
Hooking up your gauges can do several things to harm the performance of the system over the long run. Maybe not today, but the overall lifespan of the system can be affected.
We feel like 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 small amount of contaminants that the system has never seen before.
Moisture and air from one system can easily be transferred to another system. This is 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 create a new mixture, a new refrigerant even, where if done enough times will throw the readings off on a system so badly, not even the most experienced techs will be able to tell the true pressures inside that system.
This will eventually create a situation where a technician down the road will tell the customer they need to remove all the refrigerant and start over with a new manufacturer’s charge of virgin refrigerant to determine if anything else is wrong with the system.
Another reason to avoid putting your gauges on every time you go out on a call is to reduce the chances of exposing yourself to refrigerant burns.
In the unlikely event that you find like 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 those hoses off and burn themselves in the meantime.
We know it’s a small chance but tell that to the techs who have ended up with huge blisters on their hands trying to play the hero – losing time off work, further impacting their paychecks and livelihood.
Our last point we want to make in persuading you to think twice about hooking up your gauges to every AC system you come upon, is the fact that the Schrader core we spoke of earlier 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-tightly. Lefty-loosey.
Taking off your hoses in the normal counterclockwise direction mimics the same direction it takes to unscrew the Schrader core.
We’ve seen it a few times already when we went out on a service call for no cooling. The client said the system only blows room temperature air. They also said they have been having maintenance done by a local company every spring and fall.
There was no temp split from the registers, and the suction line at the AC was warm to the touch. We unscrewed the service valve cap to attach our hoses and when we got the cap off, we saw a small amount of liquid refrigerant spewing out of where the valve core sits.
We think we’ve found the problem.
To put it another way, ACHR News had a story recently saying, “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.”
They went on to say 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.
Remember, only virgin refrigerant is supposed to be in these systems. So, the less we go from system to system putting on and taking off our refrigerant hoses will not only save time, but it will increase equipment life, maintain performance, and reduce refrigerant emissions to the atmosphere.
Like we said at the beginning, we were told by the company trainer to hook up our manifold gauges every time we’re out on an AC call.
They said it would make us look like the doctor who wears a stethoscope around his neck. They said our customer expects to see those hoses hooked up, and if they weren’t, they might think something wasn’t right.
We just think he wasn’t worried about the integrity of the customer’s AC system or the integrity of his company’s high-pressure sales antics.
So the next time you need an honest AC system check up – call Red Deer Heating and AC.

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