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Battery Connection Notes and Replacement
 
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Pelican Technical Article:

Battery Connection Notes and Replacement

Steve Vernon

Time:

30 minutes30 mins

Tab:

$0 to $200

Talent:

*

Tools:

13mm, 10mm wrench

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Battery

Hot Tip:

Store any aftermarket radio codes you may need

Performance Gain:

Car starts

Complementary Modification:

Change air filter

The battery for the W123 is located in the rear right corner of the engine bay. When replacing your battery make sure to use a high quality unit; they tend to last longer than the cheaper ones. Replacing the battery is easy and can usually be done in less than 30 minutes. This is a great job to start your DIY journey on and working safely with your battery is an important aspect of fixing things yourself.

Before disconnecting your battery, remove the key from the vehicle and store in a safe place and note any radio presets. When a battery is reconnected or loses its charge you may have to reset your stereo and clock (if equipped).

The battery for the W123 is located in the rear right corner of the engine bay.
Figure 1

The battery for the W123 is located in the rear right corner of the engine bay.

If you need to jump start your vehicle you do need to directly connect the jumper cable to the battery.
Figure 2

If you need to jump start your vehicle you do need to directly connect the jumper cable to the battery. When jump starting: Be sure to work in a well ventilated area, batteries can produce an explosive gas. Wear gloves and eye protection and if battery acid comes in contact with your skin, immediately flush the area with water and seek medical assistance. Move both vehicles close together but do not allow then to touch. Turn ignition OFF in both vehicles. Connect one end of positive jumper cable to positive (+) battery terminal of the vehicle with the good battery. Slide back the protective cover (if equipped) and connect the other end of the positive jumper cable to positive (+) junction terminal (red arrow). Connect one end of the negative (-) cable to the negative (-) battery terminal of vehicle with good battery. Connect the other end of the negative (-) jumper cable to a known good ground on the chassis (yellow arrow). Start the engine on vehicle with good battery. Allow it to idle and then raise the engine to 2000 RPM. Next, start engine of vehicle with discharged battery. Once vehicle with discharged vehicle starts, shut OFF any electrical accessories, radio, HVAC blower, etc. Carefully disconnect the jumper cable in the reverse order that you connected them. Allow vehicle with dead battery to idle to recharge the battery.

If you are replacing the battery there are three areas you will need to work on; the ground strap (red arrow), the positive strap (yellow arrow) and the bracket that holds the battery in place (blue arrow).
Figure 3

If you are replacing the battery there are three areas you will need to work on; the ground strap (red arrow), the positive strap (yellow arrow) and the bracket that holds the battery in place (blue arrow).

Figure 4

The battery is grounded from the battery; to the chassis (red arrow)

If you are removing the battery or want to disconnect it to make it safe to work on the electronics, like the starter or alternator, use a 13mm wrench and remove the ground strap from the negative post on the battery (red arrow).
Figure 5

If you are removing the battery or want to disconnect it to make it safe to work on the electronics, like the starter or alternator, use a 13mm wrench and remove the ground strap from the negative post on the battery (red arrow). Always set the strap in a position that it can NOT accidentally come in contact with the negative post while working.

Next remove the positive strap from the positive post on the battery with a 13mm wrench (red arrow) and set it aside.
Figure 6

Next remove the positive strap from the positive post on the battery with a 13mm wrench (red arrow) and set it aside. If your battery has a drain tube disconnect the drain hose from it now

There is a bracket on the bottom of the battery tray that holds the battery down (red arrow).
Figure 7

There is a bracket on the bottom of the battery tray that holds the battery down (red arrow). Use a 10mm wrench and remove nut and bracket (red arrow).

Carefully lift the battery out from the engine compartment making sure to hold it upright and level.
Figure 8

Carefully lift the battery out from the engine compartment making sure to hold it upright and level. The battery is heavy and if you have any concerns about lifting it get a friend to help. Before installing the new battery make sure to the check the condition of the tray. If the tray has any acid damage use some baking soda to neutralize it or better yet remove it, clean it and repaint it. Installation is the reverse of removal.

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Page last updated: Sat 12/3/2016 03:06:17 AM