Removing Regulator Sensing Relay and Generator/starter Relay from GMPD4106

[Fred Mc]

In an attempt to simplify some wiring and correct some electrical issues I bought two manuals from Coach Info to do this. Both manuals tell you how to replace the relays with magnetic switches. The manuals seem pretty comprehensive and appear to be specifically written for "electrical wiring challenged "people like myself.
Has anyone else used these manuals or replaced these relays?
Interestingly, the most expensive part of these procedures are the manuals. In other words they are cheap modifications.

Regards

Fred

[Oonrahnjay]

       What's the difference between a relay and a "magnetic switch"   (Seriously, not being critical or a smart @$$, I would like to know.)

[Fred Mc]

Not sure exactly what the difference is.But for one, its 50 years newer and secondly, it seems to cut out a lot of redundancy The less to go wrong the less goes wrong.

[richard5933]

I'd be very careful in checking this out thoroughly before pulling out anything. The system in the 4106 is complex and not as straightforward as some would like, but it has worked for decades.

Our 4106 still has a pretty much stock electrical system. There are a lot of interconnected systems including charging, air, a/c, etc. What may seem like redundancy may be important to keep and have slightly different reasons for being present.

Whenever I see a manufacturer put redundant systems in place, my first assumption is that there is something so important involved that the engineers decided to put in two of them. Being a 'belt and suspenders' kind of guy, I'm hesitant to delete these systems.

All that said, I'd love to learn more about what you'd be replacing the OEM systems with as well as what type of problems you're experiencing that you're attempting to fix.

Richard

[bevans6]

I suspect, and would love to find out more, that what they are calling a magnetic switch is what I call a reed switch, or a magnetically controlled switch.  You see them as two part sensors to know when a window is open or closed, and so on.  They have contacts inside the switch half that close when the magnet half gets near.  Not new tech, very old tech actually.  There is a version called a reed relay that is fully self contained where the magnet is a coil mounted near or around the contacts.  It just functions exactly as a relay - control leads, switched leads, can be any common configuration.  It's still an electro-mechanical switch, just fewer moving parts than what you expect in a normal familiar relay. 

We use relays in two ways - as remote control switches - switch on dash controls something in the engine bay - and as current levers - small switch far away uses very little current in the wiring to control a larger current relay very near the load.  Most of the relays in the bus are DPDT (double pole double throw), they have one control coil that operates two separate switches, each can be either normally open or normally closed.  So the same relay can control two separate functions and turn them either on or off when triggered.  So the same relay can be switched and turn one load on and the other load off at the same time.  Relays are kind of fun, to be honest.

Brian

[Fred Mc]

In the manual it shows what looks like an old fashioned starter solenoid.I just replaced one on my 1947 tractor a while ago.

Here is a picture. The bus also has a number of these already.

Richard:
One of the relays I want to replace is the "Generator starter Control relay". It currently controls the starter as well as supplies current for the "regulator sensing relay" (which I also plan to replace) and the "heat and A/C blower motor control relay" (which will be moved to a circuit controlled by the master switch). It also eliminates the "no charge indicator" on the dash requiring the installation of a voltage gage. (I had previously installed a volt gage as it was part of a panel to charge my gps and iphone.) The volt gage proved invaluable when my regulator malfunctioned allowing the charging to the battery to fluctuate from 12 volts to 16 volts( which I was able to control through engine rpms so I didn't fry the batteries).
One other thing it also eliminates is an interlock  so the starter cannot be energized once the engine has been started.But I have been driving for over 50 years and this hasn't been a problem for me yet.

Regards

Fred

[richard5933]

I'm interested in seeing how this works out and what you end up keeping and/or tossing overboard. My understanding of all this is still preliminary. I'd love to sit and talk with the engineers that put this system together to get a first-hand understanding of the logic flow they designed.

My assumption is that they built in multiple layers of protection since the vehicles were going to be operated by employees and not owners. Since we have a lot more skin in the game than the company drivers, it seems that we would by nature be more careful with the operation. That said, I have been helped more than a few times by built-in safety features/tell-tales.

Please keep the information flowing as you make the changes.

Richard

[bevans6]

I don't see any particular reason not to eliminate the blower/no-gen relay.  It's biggest reason for existing is to make sure the stock very high current AC condenser and evaporator motors can't be on if the engine isn't running and the alternator generating electricity.  If you don't have those motors, you don't need the relay.  If you do have them, the problem is yours to deal with if you make a mistake and leave them on.  The generator/starter relay just sounds like a way to control the voltage regulator, probably turning it off until air pressure builds up or something, so the alternator load is removed when starting the engine and the engine is cold.  Useful but not really required.  Without it the alternator will always be on if the engine is running, I would expect.

The relay you show is indeed just a highish current single pole single throw electro-mechanical relay.  And yes, there are a ton of them on old tractors, Fords, British cars, and all sorts.  My bus has one for the starter relay that controls the starter solenoid, and it had one for the reverse solenoid but I took it out when I converted to automatic.  Are they calling that a "magnetic switch"?  I like using those for intermittent ON applications but I don't like them for "always on" applications.  They have fairly heavy contacts and springs inside and they draw a reasonable amount of current to keep them closed against the spring pressure.

[chessie4905]

They make that style of relay in intermittent and constant duty.Be sure to use the correct one for your particular pplication.

[Fred Mc]

Is there a way to distinguish between the two?. All I see are 3 or 4 pole relays.

Thks

Fred

[bevans6]

Not from the outside, unless it's stamped on which is unlikely.  It will be in the specification in a catalog somewhere.  The relay can be normally open, closed when powered (like a starter solenoid, only turns on the starter motor when the starter switch is pushed) or normally closed (only opens when the switch is pushed, otherwise always on).  Single pole means there are two switched terminals (the big ones in your picture), single throw means it only does one thing, on or off.  Continuous duty means it's happy being on for a long time, example is the very similar relay that controls the big fan motors for the stock heater fan or the air conditioning condenser fan.  It looks just like that but is designed to be turned on and left on for many hours at a time powering up a significant load.  Intermittent means only turns on a load for a few second at a time.  I would think it would be very common for a solenoid like that to be rated for both kinds of applications, but you need to look in the catalog to know what current it takes to turn on (or off), and what current it can switch.  It would help if you could show us or tell us how you actually plan to use them.  If I was removing the relays you suggest, I probably wouldn't replace either of them, I would hard-wire around them.   But it depends on what you are trying to accomplish.

Brian

[Fred Mc]

The plan is to replace two relays.
One is to replace the Regulator sensing Relay which is designed to supply power to the positive side of the voltage regulator. This will obviously be continuous  duty.

The second one is to replace the generator Starter Control Relay. This will be for starting so will not be continuous duty.

Regards

Fred

[chessie4905]

I bought mine at NAPA. Their catalog listed specs and whether it is continuous duty.

[MrCrowley]

       What's the difference between a relay and a "magnetic switch"   (Seriously, not being critical or a smart @$$, I would like to know.)

Yea a relay basically used current to activate like a magnet hmmmm


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