Distributor Testers Descriptions

One of the top questions I get about distributor testers is what is the difference between the models. Sun started making distributor testers in the mid-to-late 1940's. The main tester was a "Master Model", which had four meters: RPM & dwell meters on the left and vacuum & battery voltage meters on the right. RPM meter max was 2000 distributor RPM. (Note: distributor RPM is half engine RPM, so double whatever the RPM meter max is, in this case 4000 engine RPM). The Master Model was produced on into the mid-1950's along with the "Standard Model".

The Standard Model was a three-meter tester with RPM, dwell & vacuum meters. It had smaller meters, all on the right side of the tester. Distributor RPM was increased to 2500 RPM. Both the Master & Standard testers had a distributor specifications scroll on top of the machine.

In 1959, the machines started to look a little different and now had model numbers on top of the machine. The model numbers seem to have no real order in that the first ones (oldest) were the 600 & 680. All the others (newer models) that follow are lower numbers.

The 600 is a four-meter tester with RPM & dwell meters on the left and condenser & vacuum meters on the right. RPM is now 3000 with a 4000 option.

The 680 is a two-meter tester with a unique dual RPM/dwell meter on the left & vacuum meter on the right. RPM was 3000 with a 4000 option.

Around 1963, the 500 & 400 models came out to replace the 600 & 680. The 500 is a four-meter tester with RPM & dwell meters on the left and condenser & vacuum meters on the right. Standard RPM is 3000 with a 4000 option.

The 400 is a three-meter tester with RPM, dwell & vacuum meters on the right. Standard RPM is 3000 with a 4000 option.

The 400, 500 & 600 had a D-cell and a AA battery that needed periodic changing. The 680 had a single AA battery.

In 1969, the 504 & 404 came out. An internal transformer replaced the need for batteries, and both models now had a standard RPM of 4000. Both had a dual range RPM meter with a toggle switch to switch between a 1000/4000 scale on the meter face.

The 504 is a four-meter tester with RPM & dwell meters on the left and condenser & vacuum meters on the right. Standard 4000 RPM. Early models had mechanical vacuum pumps and later ones had electric vacuum pumps.

The 404 is a three-meter tester with RPM, dwell & vacuum meters on the right. Standard 4000 RPM. Early models had mechanical vacuum pumps and later ones had electric vacuum pumps.

Also produced around this time was the 506. It is a four-meter tester with RPM & dwell meters on the left and condenser & vacuum meters on the right. The 506 was different in two ways. RPM was a screaming 0-6000! That's 12,000 engine RPM. It was the only distributor tester Sun made with a white xenon flashtube, all the others being orange neon. Those models were produced into about 1978.

All the testers used vacuum pumps. Some were mechanical pumps that ran whenever the machine was running and some were electric pumps that had a on/off switch on the front case.

The last model was the EDT-5001 produced in Brazil at a Sun-owned plant. It was much different from the earlier models, with modern circuit boards and no flashtube. Mechanical advance was read on an analog meter. Production ceased in the 1980's.

To sum things up, what we have are four-meter or three-meter machines that can spin probably any distributor you can come up with. Sun made different adapters for different kinds of distributors. When electronic distributors started coming out in the 1960's & 70's, Sun produced a pulse amplifier to trigger the tester.

If any Sun experts can add any information, I would be glad to hear from you.