A lot has happened in the last few months. I've built a handful of cold start relays (v4). Great fun and have gotten to know several folks quite well as we worked through their cold start wiring systems.
During one of the troubleshooting efforts (one Tii had a starter that wouldn't stop, but only when the cold start relay was installed!) I moved on from v4 of the board to v6! This follows the design changes from Bosch. I'm not sure we will ever know the motivation behind the slight c
Solid success today. Received the two new boards on Monday and built them today. Looks really good, the spade connectors are solid and tight, the components all fit.
Soldering it up:
Ran it in the test rig and works!
However still one more iteration. Sharp eyes will see where I had to enlarge one of the notches for it to fit the black plastic housing.
Took longer than I had hoped but I'm glad to report that v3 of the board design is complete. I had to modify the original design to support the new relay design (since the OEM is NLA), and then add a daughterboard to support the 6 spade connectors.
The photo shows the mockup of the board using paper. Its a decent way to sanity check measurements. I was off width by 1mm and height by 1 mm. Height isn't a big deal but width is since the board fits into the aluminum box.
<TL:DR - the new board has been built and appears to work as designed! New post coming soon!>
I've learned a lot during this project. While the goal has always been to build a reproduction board, I also wanted to better understand the cold start circuit itself. Questions I wanted answered include: How do the components work together? What is the sequence of events? And eventually - is there room for modification?
I've found that the system behavior is different than
Progress on the test harness has moved faster than my blogging. ?
I'm excited - harness complete and used to test three OEM cold start timers. One works. The other two have peeling solder traces. Fixable but I won't spend time right now repairing them - once one spot is fixed its only time before another bit pops up.
Super interesting to see the behavior of the system. I'll document it so that folks know exactly what is happening when you turn the key. Have to say it's di
Prior to building a cold start relay I examined the two boards I have.
Both are out of '73's and are identical in general appearance. By that I mean they appear to be the same circuit board schematic and all passive components are present. Here is the front and back of one of them:
However, the values of some resistors and transistors vary between the two boards. Could be several reasons for this - the system is much more forgiving than I realize and so it doesn't m
We've had two '73 Tiis for about 20 years. Neither car has working cold start timer boxes. Both have the manual cold start injector bypass button under the dashboard.
Both cars run well and always start. They have been without a timer box for so long I stopped thinking about it.
I originally considered about modernizing the timer circuit. Build it out of a micro-controller, a voltage regulator and a relay, jam it all in the box and call it good. However, a few years bac