Underhood Detectors: And the Answer is ...
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Underhood Detectors: And the Answer is …

Being a professional technician is a bit like being a detective every day, says Mike DuBois. You are presented with “evidence” and expected to solve the crime. Sometimes the clues are obvious and other times all you have to work with is a dead body.

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Colonel Mustard in the library with a candlestick! Now admittedly, some of you have no idea what that sentence means. For others of you, this will bring back childhood memories fond or otherwise. This obscure reference is from a board game called Clue. The object of this game was for players to figure out who committed a crime and how.

Being a professional technician is a bit like that every day. You are presented with “evidence” and expected to solve the crime. Sometimes the clues are clear and obvious and other times all you have to work with is a dead body. The corpse might be a locked up A/C compressor, a check engine light, a misfire/no start condition or some fluid where it shouldn’t be.

This article hopefully will help you think of new and different methods to solve the mysteries that present themselves to you.

For the most part, your mysteries involve finding things that are hard to see; and analyzing information “clues.” These come in multiple forms and varieties. Below are some ideas about those clues and the tools that can provide them to you.

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Smoke Machines
This seems like a good place to start in staying with the theme of mysteries and clues. I don’t have to tell you that today’s modern vehicles have miles and miles of hoses, tubing and vacuum lines. These lines do a host of jobs ranging from carrying fuel or fuel vapors, to providing vacuum signals needed to operate components such as power door locks, air conditioning controls, opening and closing valves and solenoids and many more things.

The problem with working on and diagnosing these lines and hoses is that the manufacturers have a habit of putting them in the most inconvenient and down-right nasty places they can think of. As you well know, it isn’t usually the replacing the bad item that is the most difficult; it is the finding the bad item that is tough. Smoke machines are fast becoming a must-have tool to do repairs and diagnosis on vehicles. Initially, these tools were primarily designed to help diagnose emission and evaporative control systems. By injecting smoke into a closed system, you can quickly find leaks that would otherwise be difficult if not impossible to find.

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When diagnosing leaks in fuel and evaporative systems, it is necessary to inject a stable and non-explosive gas to avoid explosions due to injecting oxygen into the fuel system. The gas of choice for this is nitrogen. When making a buying decision on a smoke machine, be sure to find out if it can use nitrogen. The tool should include a regulator, tubing and instructions on how to use the nitrogen when diagnosing evaporative leaks.

Refrigerant Leak Detection
A/C refrigerant leak detection can be accomplished a couple of different ways. The two main ways are either via electronic “sniffers” or electronic refrigerant leak detectors; or by using ultraviolet light and dye. Both of these are good methods and can provide good results when used correctly. The reality is that neither of these are the solution all the time and you will need to use one and sometimes both to determine for certain where leaks are on a vehicle system. 

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Today’s electronic leak detectors are highly sensitive and accurate to levels far smaller than ever before. When purchasing electronic leak detectors, some of the most important questions are warranty policy, replacement parts, accessories and the availability of consumable items. You also want to check to see if the tool uses replaceable batteries or an internal rechargeable battery. Does the tool have both visual and audible alarms? It is a nice option to be able to decide if you want to “see” or “hear” the alarm indicating a leak. Is the alarm rate adjustable for different sized leaks? Can you use an earphone or bud with the tool? That can be a nice option as well.

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Ultraviolet leak detection is a great solution for working in areas that are tight and may be difficult to get an electronic probe into. The principal is quite simple; you can introduce a dye agent into any system in the vehicle that carries a fluid. This can include refrigerant, oils, coolant, hydraulic fluids such as power steering, transmission and differential. After letting the dye agent circulate for a short period of time, you can use specially designed UV lights in conjunction with fluorescence-enhancing glasses to see where the dye is leaking out of the system you are testing.

When purchasing this type of equipment, you will want to check to see what is the power source and light type. Some suppliers will sell a blue light and call it UV. This is not the same thing and most dyes will not fluoresce well or at all when using blue light. You also will want to find out if the light source is LED versus some other technology. Light type will significantly affect battery life. Find out what the battery type is, either disposable or internal rechargeable. Does the kit come with glasses? How about dyes? Check on the cord length if it is a DC power off the vehicle’s battery. Does the kit include a storage case? These are just a few of the things you will want to verify before purchasing.

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You also need to verify which method of delivery you want. There are two main groups with some size and styles below that. The most common is the injection system using the supplier’s tool. These often look similar to a caulking gun. They use cartridges of dye designed to fit that supplier’s tool. They come in various volumes and for the different parts of the car discussed above.

The second method of installation is bulk. This is where you pour liquid dye into an injector and then insert the dye into the car. This can be a cost savings in some instances. You will have to decide for yourself which method you prefer.

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One final note, find out if your distributor carries the replacement dye and in what sizes. If you are a high volume shop, you will want to check on the larger sizes of dye.

Refrigerant Identifiers
Twenty years ago, refrigerant identifiers were not discussed much or thought of. Today, if you don’t have this tool you can be in for some unpleasant surprises. As the name states, this tool is used to identify refrigerant type and purity. Both of these things are extremely important to not only you as a technician, but also to your shop owner and the customers whose cars you work on.

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There are really three things you want to know about refrigerant before you install it in a car, buy it or remove it from a customer’s car.

1. What refrigerant is it?

2. Is it pure refrigerant of one type?

3. Are there any other chemicals or additives in the system or product? (This last one is really important during diagnosis). It could be just air or something worse. You are looking for the presence of mixed refrigerants, hydrocarbon-based refrigerant, stop leak, oils and anything that isn’t pure refrigerant.

It makes good sense to test every car that comes into your bay before hooking up to it. This protects you and the equipment you use. It also can help protect the customer. By knowing what is in the system first, you know how to proceed with diagnosis and repair.

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Leak or Sealant Detection
This is becoming a critical part of A/C diagnosis and repair. The availability and ease of use of stop leaks for the DIY customer is greater than ever. This product has been presented as the quick fix for every non-working A/C system on the road. The product can be useful and actually fix certain kinds of leaks under specific conditions. However, some stop leak products can damage recycling equipment during the recovery process. It is a good idea to test for the presence of stop leak in your customer’s car if you suspect the vehicle’s owner attempted prior repairs.

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Flashlights
One tool every great detective should never be without is his (or her) trusty flashlight. Auto technicians are no exception to this rule. There are so many places on vehicles that are difficult to see without the aid of additional light. There are some amazing new products available now to help the technician. These lights range from micro size LED lights that pack a big punch all the way up to monster size lights. LED lights have pretty much become the benchmark of lighting. This technology provides great light, long battery life and great dependability. You can find lights with sizes and styles to fit your needs and personal taste.

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The key to being a great detective under the hood is to pay attention to the clues. If you invest in some or all of the previously mentioned tools, you will be sure to be able to solve all the mysteries that come across your path as an automotive detective.

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