The word dirty can mean just about anything that's not sparkling clean. Please know that your evaporator does not have to be sparkling clean to cool your home efficiently. Small layers of dust does not warrant a $500-1000 cleaning job!
The key word to look for is impacted/blocked. It is then that your system will have poor performance and you should have it professionally cleaned.
How do you know if its impacted? Plain and simply ask yourself: can air get through? Can you see the copper tubes behind the fins?
Don't let a sales guy manipulate the "grey area"! Sherlock Homes will guide you in how to wisely invest your money, and not dish out hundreds just to make things look better.
The main concern that a south Texan homeowner should have about their furnace is if there's a literal hole, the main question is: are there fumes going inside the air supply?
A quality carbon monoxide detector will detect CO in air supply should there be even the tiniest hole.
Go by just the facts and avoid all opinions with Sherlock Homes!
Whenever your system is condemned by a "short to ground", always ask for the number of ohms the actual motor is reading to ground. There's 2 different types of shorts:
1. A direct short is less than 100 ohms (not followed by the letter m!) and will render all motors useless. Motor will need to be replaced.
2. A hard short is when the meter will read a very high number, usually followed by the letter "m" (megohm). This can pass in most cases! In residential, the only time this would be condemnable is if you have an invertible compressor, which are usually on mini splits.
We at Sherlock Homes pride ourselves on giving only scientifically accurate terminology to our members, without manipulating the facts!
"To buy, or not to buy," that is the question only YOU will answer upon getting the clear-cut facts from a HVAC detective.