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Topic: Boost Solenoid Oil Pressure Switch ? Replacement Alternative (Read 483 times) previous topic - next topic
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Boost Solenoid Oil Pressure Switch ? Replacement Alternative

Yahoo Message Number: 74111
Hi Coach Owners.

When the oil pressure switch fails, instead of replacing it, consider the following.
From the ignition switch, connect a switch and a relay in series so that the relay contacts make a parallel connection to the Boost rocker switch contacts on the driver's side panel. With the ignition on and setting the added switch to On, the added relay is energized whose contacts close to provide a connection parallel to the Boost switch contacts. The switch can be mounted inside the left cup holder.
About 10 years ago, I posted the addition of a LED wired across the Boost Switch contacts for an indication that the OEM oil pressure switch was working (msg 1685).

Pros

For those with solar panels, it allows the panels to charge the house batteries during the day while driving (added switch not On). There is no conflict between the solar controller and the alternator outputs. This provides a better maintenance voltage level from the solar charge controller for the house battery bank.
$10 fix without having to under the engine to replace the OEM oil pressure switch.

Cons

Forgetting to turn On the added switch during non daylight driving hours.

Fred Kovol

2000 Allure 30593

Boost Solenoid Oil Pressure Switch ? Replacement Alternative

Reply #1 –
Yahoo Message Number: 74144
I like the idea, but just to be a fuddy duddy, one more possible Con (as for the Pro re solar to be the case, the oil pressure switch has to be disconnected or inoperative):
If you leave the new switch on, and leave the ignition switch on but engine not running (anyone or their wife ever left ignition switch on after putting out the slides?), then any load can kill both sets of batteries.
I've left ignition switch on and had chassis voltage drop to well below ability to start engine, the Battery Boost switch did its job and started the engine so alternator could recharge chassis batteries. Had I had that switch, and left it on, I'd have quite possibly been unable to start either engine or generator, without an external charger (which I always carry, but not everyone does, nor always has access to 120v).
This con could be fixed with a little additional complexity, such as having a voltage trigger (comparator or Schmitt trigger?) on the relay's +12 hot from ignition, so that relay was only active if ignition source was > say 12.5 volts (which should always be the case with alternator running) or even lower say 12.0 if you wanted (but still sufficient for chassis batteries to start engine).

-Jim