Faulty fuel pump relay caused by cracked solder joint
#1
09-24-2021, 03:29 PM
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Faulty fuel pump relay caused by cracked solder joint
I'm writing on behalf of my friend who would like to share this information with other classic Volvo owners. I offered to write this for him, since he did not know where to write this.
My friend owns a Volvo 240 from 1990. The other day the car stopped working and I helped him debug. We found out that it was the fuel pump relay that was faulty, and installed another one, which fixed the issue. However, later he put the old fuel pump relay back and now the car worked again. He is an experienced electronics engineer (old school) so he wanted to find out what was causing this intermittent error. According to my friend and his classic Volvo mechanic, this is a relatively normal issue, that these relays stop without the cause being evident.
He looked at the small circuit board inside the relay housing under a magnifying glass, and was able to see a solder joint that had cracked due to metal fatigue. It was the solder joint between the relay coil and the print that had given up. This is likely to be because the relay is a heavy component and vibrations of the relay put strain on the solder joint between the board and the relay.
Instead of simply replacing the relay. He suggests that others resolder the relay pin to the board. He furthermore suggests wrapping a thin copper core (from a multicore cable) around the pin on the solder side before soldering. This will help increase the surface area of the solder joint and let it bond to a larger area of the copper trace on the circuit board. That way it is very unlikely to ever break again.
We hope this information will eventually help someone
Sincerely Steen and Thomas
My friend owns a Volvo 240 from 1990. The other day the car stopped working and I helped him debug. We found out that it was the fuel pump relay that was faulty, and installed another one, which fixed the issue. However, later he put the old fuel pump relay back and now the car worked again. He is an experienced electronics engineer (old school) so he wanted to find out what was causing this intermittent error. According to my friend and his classic Volvo mechanic, this is a relatively normal issue, that these relays stop without the cause being evident.
He looked at the small circuit board inside the relay housing under a magnifying glass, and was able to see a solder joint that had cracked due to metal fatigue. It was the solder joint between the relay coil and the print that had given up. This is likely to be because the relay is a heavy component and vibrations of the relay put strain on the solder joint between the board and the relay.
Instead of simply replacing the relay. He suggests that others resolder the relay pin to the board. He furthermore suggests wrapping a thin copper core (from a multicore cable) around the pin on the solder side before soldering. This will help increase the surface area of the solder joint and let it bond to a larger area of the copper trace on the circuit board. That way it is very unlikely to ever break again.
We hope this information will eventually help someone
Sincerely Steen and Thomas
#2
09-27-2021, 01:30 PM
Senior Member
Relay
I'm writing on behalf of my friend who would like to share this information with other classic Volvo owners. I offered to write this for him, since he did not know where to write this.
My friend owns a Volvo 240 from 1990. The other day the car stopped working and I helped him debug. We found out that it was the fuel pump relay that was faulty, and installed another one, which fixed the issue. However, later he put the old fuel pump relay back and now the car worked again. He is an experienced electronics engineer (old school) so he wanted to find out what was causing this intermittent error. According to my friend and his classic Volvo mechanic, this is a relatively normal issue, that these relays stop without the cause being evident.
He looked at the small circuit board inside the relay housing under a magnifying glass, and was able to see a solder joint that had cracked due to metal fatigue. It was the solder joint between the relay coil and the print that had given up. This is likely to be because the relay is a heavy component and vibrations of the relay put strain on the solder joint between the board and the relay.
Instead of simply replacing the relay. He suggests that others resolder the relay pin to the board. He furthermore suggests wrapping a thin copper core (from a multicore cable) around the pin on the solder side before soldering. This will help increase the surface area of the solder joint and let it bond to a larger area of the copper trace on the circuit board. That way it is very unlikely to ever break again.
We hope this information will eventually help someone
Sincerely Steen and Thomas
My friend owns a Volvo 240 from 1990. The other day the car stopped working and I helped him debug. We found out that it was the fuel pump relay that was faulty, and installed another one, which fixed the issue. However, later he put the old fuel pump relay back and now the car worked again. He is an experienced electronics engineer (old school) so he wanted to find out what was causing this intermittent error. According to my friend and his classic Volvo mechanic, this is a relatively normal issue, that these relays stop without the cause being evident.
He looked at the small circuit board inside the relay housing under a magnifying glass, and was able to see a solder joint that had cracked due to metal fatigue. It was the solder joint between the relay coil and the print that had given up. This is likely to be because the relay is a heavy component and vibrations of the relay put strain on the solder joint between the board and the relay.
Instead of simply replacing the relay. He suggests that others resolder the relay pin to the board. He furthermore suggests wrapping a thin copper core (from a multicore cable) around the pin on the solder side before soldering. This will help increase the surface area of the solder joint and let it bond to a larger area of the copper trace on the circuit board. That way it is very unlikely to ever break again.
We hope this information will eventually help someone
Sincerely Steen and Thomas
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