K6JRF at the mic K6JRF's Page
formerly W6FZC

My Mercedes Benz
S500 Coupe

K6JRF's MB S500 Cpe
(Update: Jul 8, 2010)

Analyze and Troubleshoot "Check Engine" MIL and Electronic Control Units (ECU)!

Repair of Schumacher PS1562A Battery Charger/Maintainer

Schumacher Battery Charger/Maintener

PS1562A Not Charging
I decided to charge the 2nd car's battery since it's been inactive for two weeks. Normally, it is driven daily and that action keeps the battery 'decently' charged.

While charging the battery, I noticed that the voltage wasn't rising as it should during the "charge" cycle even though the yellow LED was illuminated. A voltmeter confirmed that suspicion as it measured 13.5V. If it's working ok, the terminal voltage s/b 14.7V and rising during that cycle.

Details of the normal operation of this charger here.

Ckt Board + Transformer Removed The unit comes apart easily; remove the two (2) bottom screws and the covers (top and bottom) come apart revealing the internal parts. There's no need to unsolder any wires from each sub-assy, just move them out of the way.

Next remove two (2) screws that hold the Printed Circuit Board (PCB) in the case; lift out and inspect for "damage". In my case, I found that the fuse, Littelfuse 10A/32V PCB model was blown. That's easy enough except I don't have replacements for it. So I used a mini fuse 125V / 6.3Amp rating for temporary use until the replacement PCB Mini fuse is received. This fuse is esp made for PCB board use and is soldered into the board.

I could have soldered a jumper wire across the fuse terminals but decided against that b/c there wasn't any obvious damage. A 'reckless' jumper could cause it to 'fry'! Better to be safe than sorry!

PCB Repair
Schumacher PCB showing circuit detail To replace the fuse, desolder the blown fuse and clean the botom side of the PCB so you can insert the replacement fuse. Even though the heat sink 'shadows' the fuse, it is possible to insert the new fuse without removing the heat sink. After that, turn the unit over so that the backside is accessible, then solder the fuse into place. Cut the tab "tips" off. The fuse "detail" is shown on top of the transformer.

Info on Littelfuse FP1 PCB Fuse: here.

Each fuse is $2.99 in single quantities. Mouser carries most all types of parts and is an excellent source for your needs. I highly recommend them and use them often!!

Repair Complete
Schumacher Battery In Operation After replacing the fuse, the PCB is ready to install into the housing. Nothing special here but make sure you seat the power transformer properly and route the wires back into their original positions. Also make sure that you have aligned the LED stack assy properly so that the LEDS (red, yellow and blue) line up with the front panel 'view' window.

The picture shows the Schumacher Battery Maintainer in operation connected to my S500 coupe operating in the "charge" mode with the yellow LED lighted.

After two (2) years of using the Schumacher, I checked my Interstate battery for fluid loss; there wasn't any! This is the sign of a "good" charger/maintainer.

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