There are a range of considerations when buying a rear view monitor. I have written this guide in order to help you select the most appropriate monitor for your needs.
Types of rear view monitor
Sun visor monitor:- There are two types available on the market. The first replaces the existing sun visor and usually contains a DVD player as well as a TFT screen. The key thing to remember about these is that they are usually bought in pairs in order to keep the appearance of the vehicle. They can be difficult to fit as the mounting for the visor might not match the vehicle mounting. The second type clips on the existing sun visor. These are so thin they will not contain a DVD or speaker. They are located in an ideal area as usually it is in the shade which helps see the image. When sun gets onto the front of a monitor it can make seeing the image quite hard. It is important to ensure your sun visor is perfectly flat and you have room for the screen when the visor is up. They are much less likely to be stolen compared to more visible monitors.
Clip on mirror:- These come in a variety of shapes and can have Bluetooth or memory card slots. The TFT panel size can vary from a small 2.5" up to a wide screen 10". When the screen is not on the reflective surface of the glass acts like a normal mirror. This leads to a number of issues. In some vehicles there is a lot of light from things like high side windows or sun roofs. This can give reflections on the glass that make seeing the image on the screen hard. The "mirror function" of the monitor is darker than you would normally get on your rear view mirror (similar to having the dip lever on). In long vehicles like motorhomes this can make using it as a rear view mirror hard on dull winters days. They also tend to be made for larger American vehicles so you need to check it does not snag the sun visors. They can however be the ideal solution as they are mounted where you would usually look. They tend to be fairly discrete so less likely to attract the thief. They can be used as an always on rear view if you use a quality CCD camera. Watch out for split screen versions that can show two images side by side on a 10" screen.
Stand on dash:- Again you can get a variety of sizes from 2.5" upwards. The 7" is the most popular and because they are made in large numbers they are also as cheap as the smaller monitors. Although called stand on dash most of them can be ceiling mounted or glued to the windscreen in place of a mirror. Being mounted on the dash they can be hard to see the image on bright days, especially if the sun can get onto the screen. They are also very visible to the opportunist thief. It is possible to remove them from the vehicle as most have a plug and socket a short distance from the monitor. Although unplugging is easy mounting them onto the bracket is often fiddly.
In-dash:- These can be purely just a monitor or they can have a range of extras - Bluetooth, TVs, DVD, USB, memory card slots etc. If you are buying these on eBay beware of sellers not based in this country. If it does not work you have lost your money! Also the cost of sending it back for replacement is quite high and it is common for the seller not to receive it. It is very common for factories to dump their stock into auction sites when they have failed the quality control. I have lost count of the number of people with these units that discover that although the radio and DVD might work well other features do not. Sellers feedback does not usually show this as people are happy with their purchase at first. Buy from a UK based business with a published business address and a feedback score over 99.8%. I do not sell these units so I am not biased in my advice. The last thing to mention is any purchase over the value of £18 from outside the EU whether it is marked as a gift or sample may attract duty, VAT and handling fees. I have known one persons bill to be over £120 on a purchase costing £160. If you do get one of these units then they are very nice. Getting a camera to work on them can be a bit of a problem. There is usually a default in the way they are wired to prevent the viewing of an image with the handbrake off. The manual usually explains have to over-ride this.
Flip down:- These are usually ceiling mounted. They often contain DVD players and can vary in size from 3.5" up to very big. If you can fit one in your vehicle then they make a very good monitor for rear view use. They are very popular if you want them on all the time. The very small flip down monitors can often be mounted in the central part of the dash.
Wiring monitors in
The biggest problem is often getting the wires behind the dashboard or interior trim. They usually only require a positive connection to a supply controlled by the accessory switch, a negative that goes to the vehicle body and on some a connection to the reversing light to turn it on when reverse is selected. Many modern monitors now do not have the reverse light wire as the input of a video signal from the reversing camera will start it up. Monitors should never be connected direct to the vehicles battery.
Types of monitor panel
Most low price monitors use a CCLP back light. These require high voltages which is achieved by a power inverter circuit. They are prone to failure aided by the damp conditions found in vehicles especially in winter. More expensive monitors will use an LED backlight. On average these will give up to twice the life of a panel using a CCLP back light. We have found a failure rate on monitors of around 10% if they have a CCLP backlight and around 2% with a LED (over a period of 12 months). A lot of low price monitors used panels that are either seconds or refurbished. The failure rate on these can be up to 25% over a year. Unfortunately there is no way of easily telling unless you are buying from a reputable source. Again if they have no pixel policy and no contact details avoid buying from them. In the early days of our businesss we had one batch of monitors with an unusually high failure rate. The rust on the panels gave away the fact that they were not new as the factory stated. We now pay more and go for quality as in the long run it works out cheaper.
Specialist rear view monitors will almost all have two inputs to allow the use of two camera. More recent developments give up to 4 cameras in a split screen arrangement. RCA switches can be used to increase the number of inputs. On most monitors you can invert or reflect the image unsing the menu system. Most modern monitors will work with both PAL or NTSC cameras. Usually if they do not and you have the wrong video format the image will be black and white with poor frame hold.
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