For years my Saabs all had inoperative cruise control. I would collect cruise computers from every c900 in the junkyard and stockpile them. If I found a working one, I would cherish it, knowing that mine was among the rarest of the rare… a Saab c900 with working cruise control.
One day a friend suggested I try repairing it by heating up the cruise control computer to soften the solder joints. He said IT guys do it all the time. I asked my IT guy at work and he confirmed that it was called “Reflowing” and was typically used on computer motherboards that were on the fritz. Solder tends to degrade over time, developing cracks and pores that decrease the signals that can pass through them, although these fractures are typically too small to be seen. They would bake them in the oven for a short time to soften the solders to refill the cracks and pores and make them solid again. If the cracks are really bad, a paste of powdered solder and flux can be applied to help with the process.
I had my stockpile of broken cruise computers with no future except as an art project, so what did I have to lose? Here’s what worked for me.
First, be sure that you have correctly isolated the problem to the cruise control computer. Check and replace any bad vacuum lines or switches, and test your system with a known working cruise control computer if possible (check the parts list for your car on eEuroparts.com). This procedure should be considered a last resort for computers that are known to be inoperative.
1. Start by removing the plastic end plate(or the entire plastic outer cover if it’s a relay) to expose the inner motherboard
2. Soldering alloys have a melting point of around 360°F, but a lower temperature always has worked for me. Preheat the oven to 300°F
3. Set the unit on a piece of tin foil on a something less-conductive like a ceramic oven-safe plate and let it bake for exactly 8 minutes
4. After 8 minutes at 300°F, turn off the oven and let it cool down for about 10 minutes – so that the transition from hot to cold did not cause it to re-fracture
5. Once cool, take it out of the oven, put it back together, and plug it into the car to try it out
The first time that I tried this, the cruise control worked intermittently for the first run. But the next drive, it engaged and held. It’s been a year and a half now, and it’s still working perfectly. I ended up baking every one of my cruise computers and handing them out to my good friends like Hershey bars. No more stock pile!
This process has also worked for me on other small automotive computers and relays – central locking modules, ECUs, APCs, relays (especially the always broken Saab 9000 headlight relay). Just remove any removable plastic, bake at 300°F for 8 minutes and cool down. So if nothing else works, put on your apron and start baking!
* Disclaimer: *
This article is meant to be purely informational. eEuroparts is not responsible for any damage, either direct or consequential, to your auto parts, to your oven or to any person or property as a result of attempting this procedure.