View Single Post
Old 02-17-2004, 05:39 PM
TomJ TomJ is offline
Registered User
Join Date: Sep 2003
Location: Back in Colorado for now
Posts: 1,315
Re: Not enough solder is used and breaks after a few years due to vibration.

Originally posted by dieseldiehard
The root of the problem with these climate control modules is due to the factory designing a mechanical joint that used solder to carry current as well. This is a NASA "no-no." To meet good manufacturing practices all electrical connection interfaces (ie. solder joints) are to be secured with wrapping a wire to a terminal or staking before soldering, that way the solder can't flex and crystallize (a well known phenomena.) Crystallized solder does not carry much (if any) electrical current.
This is not to be confused with a cold solder joint, it is a material fracture.
I have fixed several of these CC units, and the solution is always to resolder the butt-joints where the circuit boards on the sides meet the main board.
I believe flexing occurs when the buttons are pressed, the whole assy receives force that translates as stress on the joints and over time it fractures.
Yep, that makes sense.
1984 300D Turbo - 4-speed manual conversion, mid-level resto

1983 300D - parts car

1979 300TD Auto - Parts car.

1985 300D Auto - Wrecked/Parts.


"If you don't know where you are going, any road will get you there". Lewis Carrol
Reply With Quote