REST/Booster Engine Pre-heat with DPDT Switch Modification

autostaretx

Erratic Member
socalmbcruiser said:
I must admit i'm not a big fan of aluminum wire ... even if it is copper-clad.

The wire's spec of "16 Gauge CCA (not AWG)" makes me wonder if it's thicker than copper to yield a "gauge equivalent" rating. Typically there's a 20% reduction in current-carrying capacity for aluminum wire (and CCA is given the pure-aluminum ratings). They could just be trying to tell us not to treat it as "copper".

--dick
 
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CharBWest

New member
I'm very interested in making this modification, is the that some special switch you have to get or is it readily available?
 

Aqua Puttana

Poly - Thread Finder
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autostaretx

Erratic Member
Actually, that's a DPDT-CO switch: double pole (i.e. two circuits), double throw (two "on" positions), center-off (when in the middle, neither circut is connected to anything)

--dick
 

Aqua Puttana

Poly - Thread Finder
Actually, that's a DPDT-CO switch: double pole (i.e. two circuits), double throw (two "on" positions), center-off (when in the middle, neither circut is connected to anything)

--dick
I missed that. It will still work, but a simple On On switch would be better. Any suggestions?

:cheers: vic
 

koenb

Member
I missed that. It will still work, but a simple On On switch would be better. Any suggestions?

:cheers: vic
I found this from blue sea, but can't seem to find anyone selling them online. The LED's won't work as previously pointed out in post #75.

Edit: Found the grey version for sale here different part number, LED maybe a different color blue vs. red but is irrelevant for this application. Could swap the face with a black one for a couple bucks.

The contura switches will fit with enlarging the sides of the oem switch holes, though if i did it again I would find another switch that fits the 18x36mm hole better. A fair amount of the plastic around the switch hole needs to be filed away.
 

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norths03

New member
I'm looking to do this 30 minute engine preheat mod in the near future. I live in the Rockies and have seen below zero temps and been stranded with a no start situation a few too many times. I am also installing a block heater to cover my bases. My REST doesn't blow warm for more than a minute so I'm guessing I'll have to replace my pump first. I can use Bosch part # 0392020026 for the pump correct? Plug and play?

As for the switch I like the factory look. Can I use the factory Rear Blower Switch (5103853aa) or will that not work with this wiring setup?
 

Aqua Puttana

Poly - Thread Finder
... Plug and play?

As for the switch I like the factory look. Can I use the factory Rear Blower Switch (5103853aa) or will that not work with this wiring setup?
Since nobody has answered...
I'm not inclined to look up part numbers. There are MB/Dodge crossover parts lists which may help you.

:cheers: vic
 

norths03

New member
Thanks for the reply. I'm pretty sure that pump part number is right. I'm more wondering if the OEM switch would work with your wiring idea. I guess there's no easy way to know for sure without buying it and finding out.
 

koenb

Member

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TROLL

2007 Winnebago View 23H
Thanks for sharing this info! Its pretty mind blowing how much info there is about the Espar heater out there, but how difficult it is to follow because the vast quantity of info, and then some of it contradicts itself. This post has finally given me some clarity on how to get the heater functioning how I want.

A couple questions I just want to verify:

In order to activate this engine preheater, do you just flip the new switch that was added, which activates the Espar heater and the circulation pump? Or do you also have to hit the factory REST switch for this modification to function to preheat the engine?
Do you have to turn your fan speed up and set the temp to hot?

Does anyone have part numbers for DPDT factory switches that look OEM and can be used for this? I see some mentioned but haven’t been able to easily find part numbers.
...Or abaccus mentioned using the SPDT rear defrost switch which looks great, plus a couple relays? If its possible to explain how this was done for someone who is good at following directions but not good at figuring out their own electrical, it would be appreciated!
…Or can you add a diode?

I guess the only reason to do the more involved more expensive 4 relay modification is if you don’t want the 30 minute time out so you can also use this for cabin heating? The 30 minute time out period is perfect for my goals of just being able to preheat my engine in cold weather before starting it.
 

Aqua Puttana

Poly - Thread Finder
...

A couple questions I just want to verify:

In order to activate this engine preheater, do you just flip the new switch that was added, which activates the Espar heater and the circulation pump? Or do you also have to hit the factory REST switch for this modification to function to preheat the engine?
Do you have to turn your fan speed up and set the temp to hot?
The DPDT switch of itself doesn't activate the heater. It has nothing directly to do with running the electric coolant pump. The DPDT switch interrupts any 12 volt feedback into other circuits. It also completes a 12 volt ENABLE to the Pin #7 on the heater. When the REST switch is enabled that powers the electric coolant pump and provides the 2nd 12 volt enable power to Pin #6 the heater.

Using the DPDT REST method the only fan speed is the low speed provided by the OEM REST circuit. The position of the temperature dial on the ATC doesn't matter.

... Does anyone have part numbers for DPDT factory switches that look OEM and can be used for this? I see some mentioned but haven’t been able to easily find part numbers. ...
If provided I will add the part number of a verified proper OEM style DPDT switch to the first post.

...
...Or abaccus mentioned using the SPDT rear defrost switch which looks great, plus a couple relays? If its possible to explain how this was done for someone who is good at following directions but not good at figuring out their own electrical, it would be appreciated!
…Or can you add a diode?
...
My original design used a SPDT switch with a diode to prevent 12 volt backfeed. It works fine. My 2004 has that circuit since 2014. One glitch is that if the REST heater circuit hasn't timed out, and the engine is started, it will trigger ASR, ESP fault lockouts. If that happens, the solution is to shut the engine down, wait around 1 minute to allow orderly shutdown of the ECM aka ECU, and the start the engine. There is no permanent problem.

The original diode circuit is in this post.

https://sprinter-source.com/forum/showthread.php?p=274858#post274858

:cheers: vic
 
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TROLL

2007 Winnebago View 23H
Thank you.

The DPDT switch of itself doesn't activate the heater. It has nothing directly to do with running the electric coolant pump. The DPDT switch interrupts any 12 volt feedback into other circuits. It also completes a 12 volt ENABLE to the Pin #7 on the heater. When the REST switch is enabled that powers the electric coolant pump and provides the 2nd 12 volt enable power to Pin #6 the heater.

Using the DPDT REST method the only fan speed is the low speed provided by the OEM REST circuit. The position of the temperature dial on the ATC doesn't matter.
Apologies that I’m struggling on this but i don’t know what different pins do.
In super basic laymen’s terms, when you do this modification and you want to warm up your engine before actually starting the engine, what button(s) do you press?


One glitch is that if the REST heater circuit hasn't timed out, and the engine is started, it will trigger ASR, ESP fault lockouts. If that happens, the solution is to shut the engine down, wait around 1 minute to allow orderly shutdown of the ECM aka ECU, and the start the engine. There is no permanent problems.
Will this fault also happen on the DPDT if you start the engine or would that be avoided?

And if anyone knows an OEM DPDT switch part number that is recommended and fits in the oval blank space behind/to the right of the steering wheel (not on the actual center console) I’d love to get something ordered. Assume we won’t luck out with a “heating” symbol on it but if we could that would cure my OCD. Or maybe it’s possible to remove an unrelated symbol and leave it blank?
 

Aqua Puttana

Poly - Thread Finder
Thank you.


Apologies that I’m struggling on this but i don’t know what different pins do.
In super basic laymen’s terms, when you do this modification and you want to warm up your engine before actually starting the engine, what button(s) do you press?
No problems.

My start method.
I turn on my added heater switch aka DPDT Switch in the latest circuit.

I next press the REST switch in the ATC. I believe a red LED lights on the round switch segment.

You should then hear the Espar heater fan ramp up to purge the combustion chamber and begin the Combustion Control pre-start checks.

Sometimes I wait to actually hear the heater fire off. More often I go back inside to my hot coffee.



Will this fault also happen on the DPDT if you start the engine or would that be avoided?
The later DPDT circuit that I designed will not have any glitches.

:cheers: vic

P.S. - I may drag out the modification schematic and add some clarification notes.

Here's some notes.

10.3.3 BoosterPreHeatRESTrev2e.jpg
 
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TROLL

2007 Winnebago View 23H
Interesting, thank you for clarification. So this “engine preheater” mod is basically a “engine preheater + rest” function that always operate together, which is totally fine.
Safe to assume that the ~30 minute factory timeout for the rest function also turns off the preheater function as well?

And yes if you do want to update the first post, as a noob I found your update on post 47? the most helpful so that info may serve better at the top.
Thanks for your help!
 
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Aqua Puttana

Poly - Thread Finder
...

And yes you do want to update the first post, as a noob I found your update on post 47? the most helpful so that info may serve better at the top.
Thanks for your help!
I did have a note for the wiring details in post #47. I just made it a larger font and blue color.

:cheers: vic
 

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