Unlike new millennium cars that rely heavily on computers, the antique W124 electrical system is very simple and QED [quite easy to DIY].
Jan 24th 2010
The most common problem with W124 is overheating during traffic jam if thermo fan_switch fails. Under normal driving condition with aircond ON the radiator cooling fan seldom kicks in, so no one knows immediately whether the radiator cooling fan is operational.
It is not practical to carry around a spare fan switch because I can bet the number of Merc owners who keep 22mm wrench in their car if more than one hand finger_count.
The simplest way is to keep a jumper wire c/w banana [male] connectors to short circuit the fan thermo_switch female connector in case the switch fails while driving or caught in traffic jam. Simple!
Jan 21st 2010
The W124 engine can even be cranked by a weak small capacity battery [DIN55]. The ECU won't cut off electrical power supply even though the voltage drops below nominal value.
This battery was considered dead by another sensitive car which rely too much on computer!
Jan 03rd 2010
Everytime I tekan brake pedal, fuel gauge reading drops to 'E'. Similarly when turning signal light is activated the fuel gauge needle started to dance with the same tempo. I opened up the boot and removed all the plastic covers to examine the wiring for short circuits or loose connections.
What I found was a loose earthing point at which several brown colored-coded wire were screwed to the car body. If u guys experience this just check the grounding/earthing point connections.
December 16th 2009
Aircond blower fan and compressor intermittently stops, especially when taking hard corners or hitting a speed bump. Looks like there is a loose electrical connection.
However, if either one [blower fan or compressor] stops functioning it could be more than just electrical connection problem. Well, electrical thing is my bread and butter but the access to the main electrical wiring/connector at the back of the aircond switch/speed_regulator is no easy task. It took me almost 30minutes to reach there.
__
My guess was correct. I checked the main incoming power line [the thickest wire] voltage and it was OK. Took out the connector and found out that it had become loose. Just by using a long nose pliers the female connector could be tightened back.
Jan 24th 2010
The most common problem with W124 is overheating during traffic jam if thermo fan_switch fails. Under normal driving condition with aircond ON the radiator cooling fan seldom kicks in, so no one knows immediately whether the radiator cooling fan is operational.
It is not practical to carry around a spare fan switch because I can bet the number of Merc owners who keep 22mm wrench in their car if more than one hand finger_count.
The simplest way is to keep a jumper wire c/w banana [male] connectors to short circuit the fan thermo_switch female connector in case the switch fails while driving or caught in traffic jam. Simple!
Jan 21st 2010
The W124 engine can even be cranked by a weak small capacity battery [DIN55]. The ECU won't cut off electrical power supply even though the voltage drops below nominal value.
This battery was considered dead by another sensitive car which rely too much on computer!
Jan 03rd 2010
Everytime I tekan brake pedal, fuel gauge reading drops to 'E'. Similarly when turning signal light is activated the fuel gauge needle started to dance with the same tempo. I opened up the boot and removed all the plastic covers to examine the wiring for short circuits or loose connections.
What I found was a loose earthing point at which several brown colored-coded wire were screwed to the car body. If u guys experience this just check the grounding/earthing point connections.
December 16th 2009
Aircond blower fan and compressor intermittently stops, especially when taking hard corners or hitting a speed bump. Looks like there is a loose electrical connection.
However, if either one [blower fan or compressor] stops functioning it could be more than just electrical connection problem. Well, electrical thing is my bread and butter but the access to the main electrical wiring/connector at the back of the aircond switch/speed_regulator is no easy task. It took me almost 30minutes to reach there.
__My guess was correct. I checked the main incoming power line [the thickest wire] voltage and it was OK. Took out the connector and found out that it had become loose. Just by using a long nose pliers the female connector could be tightened back.
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The electric fan can be "tricked" to start spinning at lower temperature by adding a suitable resistor across the sensor terminals.
ReplyDeleteMy W124's twin electric fans spin at 1st speed whenever air con compressor is engaged.
High speed kicks in only when temp is 100. I connected a 1.1K resistor to trick it to spin high speed at around 88
Nice tip but my car is using belt driven radiator fan [with electro magnetic clutch] which speed cannot be regulated. Its either ON of OFF.
ReplyDeleteI've also installed a relay so that the radiator fan kicks in when I turn on the a/cond. Pls see the battery pic, The relay is next to the battery.