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Technical Help


Information on older  advance units of 899 type!

Used in systems with numbers xx xx 899 xx.

Recogniseable by the existence of a single green/red wire on the unit.
also some junits had a short stump containing 2 short orange wires acting as a switch between 2 curves.

Those systems demand imperatively the existence of a 12V battery. 
# if used without battery
# or with a defective battery
# or if a fuse blows that disconnects the battery, but leaves the regulator's 12volt exit still connected to the system (thus feeding voltage to the unit) the advance unit might be destroyed by voltage peaks from the alternator.

The unit is similar to a computer that needs a stable DC voltage to operate.
This voltage arrives via the green/red wire. The voltage is stabilized by the battery.
Without battery the unit is subjected to possible voltage peaks generated by the magneto which can kill the unit.


Given the rather high probability of events as outlined above, chances of blowing that sort of unit are relatively high. (Which did eventually lead to this technology to be replaced. Later units do not have the green/red wire and hence not this problem.)


If a system equipped with such units is not sparking, it still need not mean that it is destroyed. Higher chances are that the 12V feed is disconnected somehow.

So, please check whether there is indeed 12V voltage arriving at the green/red wire. Failure of the main switch or some wire connection might be preventing voltage from arriving.


For a procedure of checking whether the advance unit might be faulty, please see here.