Boost switch

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Boost switch

December 08, 2014, 10:06:42 pm

Can the Boost switch be left on all the time? while plugged in, generator running, or while driving?
Thanks, ipatch

Re: Boost switch

Reply #1 – December 08, 2014, 10:19:33 pm

The boost solenoid has a pretty good current draw and will get hot to the touch in less than an hour. It is a non latching type solenoid so needs juice to keep the contacts closed. No reason to keep on while driving as the engine alternator charges both banks. Install a trickle charger so both charge while plugged in. Keeping it on all the time will shorten it's life and you may not know when it fails.

Using it to start all the time will mask starting battery or starting cable faults.

Pierce

Re: Boost switch

Reply #2 – December 09, 2014, 08:11:33 am

I think mine has failed. where is it and is it a generic part i can pick up at an auto supply?

Re: Boost switch

Reply #3 – December 09, 2014, 09:59:54 am

Phil,

It's a Cole-Hersee 24213. Don't let a parts house sell you an older model. See at: http://www.oreillyauto.com/site/c/detail/CH00/24213/N0791.oap?ck=Search_N0791_-1_-1&pt=N0791&ppt=C0218 If you are handy, they are user repairable.

Ignition solenoid is the same part number. Good to carry a spare.

Buy online at about a 40% discount. Solid state also available for about $150 but should last forever.

Boost solenoids are great but in my opinion, many owners use it as a crutch and it can end up hurting more than helping.

Pierce

Re: Boost switch

Reply #4 – December 09, 2014, 10:02:48 am

Quote from: philtravel – December 09, 2014, 08:11:33 am

I think mine has failed. where is it and is it a generic part i can pick up at an auto supply?

I scanned the forum, but cannot find "Where the boost solenoid is located"

Re: Boost switch

Reply #5 – December 09, 2014, 10:11:42 am

Two important criteria:

Amp rating and must be continuous duty.

Important to longevity, particularly if you use the boost switch when starting the engine (which IS a good idea, as is minimizes voltage drop under that high load): Engage the boost switch BEFORE turning the key, and disengage after it starts. That way you are not closing or opening the contacts under heavy load.

Switching under heavy load causes an arc that pits the contacts.

Re: Boost switch

Reply #6 – December 09, 2014, 10:50:27 am

of course Brett W is right on the correct use of Boost, and while on that topic as we are coming to Q (subject to nothing stopping us) if anyone wants to bring their old solenoids with them I will repair them on the spot and make them new again for free, so you have spares.
John H

Re: Boost switch

Reply #7 – December 09, 2014, 11:11:05 am

Forrest is U270 model so it only has two start batteries. I use the boost switch as Brett W describes to support the start battery bank. As I do not have shore power in the storage facility I typically have the genset running as I begin the start procedure while in storage. If I am parked at a site with shore power, then I still use this procedure minus the genset running as Forrest is still plugged into shore power prior to leaving the campground. After the coach starts, then I begin the shore power electrical shut down.

Re: Boost switch

Reply #8 – December 09, 2014, 12:12:18 pm

I have to take a bit of issue with the use of the boost switch each time the engine is started.

In the case of the very recent post, the engine batteries were flat and the engine turned over very slowly because the boost switch was turned on and the 200 amp solenoid was used to shuttle all the amperage to the starter motor. 200 amps is a fraction of what the starter needs. The associated boost solenoid cables are also not up to the amperage needed. Winter starts will require still higher draw and for a longer cranking period. Trying to send high amperage through the boost solenoid will drastically shorten the life of the solenoid and low voltage to the starter will shorten it's life also. A damaged starter is not only very expensive but can leave you stuck for days in the worst case.

Constant use of the boost switch gives the operator no idea of the condition of the starting batteries or terminal connections.

Many cars have substandard cables and RVs are not immune. I remember older GM Corvettes used aluminum cables and were reluctant starters.

To make sure your coach is totally ready to start in the winter months ahead, you need the following.

Start batteries in good condition with a bad battery necessitating the replacement of ALL the start batteries, not just the bad one. Another reason not to spend needless $$ on high priced colored batteries. If the battery is less expensive (but still high quality), owners will be more likely to replace the other one or two.

Clean terminals with military type connectors used if possible. An extra ground cable installed from the start batteries to the closest grounding point. Replacing or doubling up on the start battery to starter motor positive cable. A voltage differential check can be made from the start batteries to the starter motor while cranking. Best done in cold weather to see the maximum voltage drop.

A trickle charger installed so when the coach is plugged in to shore power or the generator is running, the start batteries will be charged.

During storage, the start batteries MUST be disconnected at the batteries if no shore power available. The battery switch will NOT do the trick as there are other parasitic losses.

Two voltmeters should be installed to be viewed by the operator while underway or parked. Below is the dedicated installation I made along with the plug in type that goes in the two lighter plugs. The Audit wires are a good source of both coach and start battery voltages. The plug in type take no skill in the installation and at about $2 each off ebay delivered or a little more from a auto parts house, won't break any bank.

Having operator viewable voltage meters will also give an instant reading as to the health of the charging system, whether while underway or stationary with shore voltage or solar panels doing the charging.

In closing, the boost switch is great for a little more amperage if the engine batteries are down. In the case of a low voltage engine battery reading, the boost switch should be turn on ahead of time to let the voltages equalize and then the starter can be used taking advantage of the much larger cables from battery to starter. Anytime the starter seems to be slow in cranking, go over the entire starting system rather than using the boost solenoid to mask any problem.

Any recommendation to use both on a regular basis by the factory is an attempt to cover up a weakness in the starting system components. The factory does not walk on water as seen in the use of Rolocks, the air cleaner intake design on many models, etc, etc.

Pierce

Re: Boost switch

Reply #9 – December 09, 2014, 12:27:48 pm

Pierce,

Totally agree-- the boost switch is NOT a substitute for good chassis batteries.

The boost switch IS a good addition of amp-hrs to a good chassis battery bank WHEN the house battery bank is fully charged.

Re: Boost switch

Reply #10 – December 09, 2014, 12:50:01 pm

My guru buddy installs the sealand magnetic latching relays in both positions. No power used to hold it together.

Re: Boost switch

Reply #11 – December 09, 2014, 01:00:02 pm

Bob,

Yes, latching relays are a good deal. They don't take any juice to keep contacts in the closed position. A good example of a latching relay is the water pump relay. One push from any pump switch location activates the water pump until a switch is pushed again from any water pump switch location to shut off voltage to the pump.

Pierce

Re: Boost switch

Reply #12 – December 09, 2014, 04:47:19 pm

Peter, We also have a U270 that came with 2 RedTop start batteries. We put in 3 RedTop batteries when we changed start batteries. The 3rd fits in the tray just fine and adds some insurance for starting.

We also agree with Pierce & Brett, and NEVER use boost when starting, even before we added the 3rd start battery.

Re: Boost switch

Reply #13 – December 09, 2014, 06:53:28 pm

Actually, I DO use boost when starting, but as mentioned above, not as a substitute for good chassis batteries and not if house bank is discharged.

Re: Boost switch

Reply #14 – December 09, 2014, 07:02:20 pm

I'm planning on using the boost switch when I start tomorrow morning. The temperature is going to be right about 32 degrees when we plan to start. I've got the block heater on now. When we left St. Peters last week it was in the 20's with winds up the tailpipe of upper 20's, so even the boost didn't really get it going. I added the Jeep to the mix and it fired.

Re: Boost switch

Reply #15 – December 09, 2014, 07:07:53 pm

What is the Blue Sea PN 9012 used for?

best, paul

Re: Boost switch

Reply #16 – December 09, 2014, 07:19:42 pm

That is a very high end/high quality "solenoid". Read the specs-- they (to use modern jargon) are "awesome".

I have used them for the ignition solenoid, but not the boost switch, on the theory that a failed ignition solenoid will STOP YOU. A failed boost switch will/should not.

Certainly it could be used for either.

Re: Boost switch

Reply #17 – December 09, 2014, 07:33:17 pm

So far I don't see an answer to the question of where the solenoid is located.

Re: Boost switch

Reply #18 – December 09, 2014, 07:57:12 pm

On my 93 U300 it is located below the isolator, on the same mounting panel. There are two solenoids there. I assume one is the starter solenoid and one is the boost solenoid, but I don't know which is which. I can hear the click when the boost switch is turned on. If I got to the point where I need to know which was which I could probably stuff myself under there and follow a red wire to the starter.

Re: Boost switch

Reply #19 – December 10, 2014, 05:25:52 pm

Quote from: kb0zke – December 09, 2014, 07:02:20 pm

I'm planning on using the boost switch when I start tomorrow morning. The temperature is going to be right about 32 degrees when we plan to start. I've got the block heater on now. When we left St. Peters last week it was in the 20's with winds up the tailpipe of upper 20's, so even the boost didn't really get it going. I added the Jeep to the mix and it fired.

David, when the temps are in the 20's our one year old, three Red Tops start us just fine. We leave the block heater on over night then it usually takes about three tries to start the engine but it always starts. If yours needs that much starting power you may need to replace your block heater, $89.00.

When temps are under 30, the Detroit can be stubborn. I never run the starter more than 10 seconds at any attempt to start. On the first try I keep the key turned so the starter supports the engine until the engine is running for a few seconds. The engine usually dies the first try after 10 to 15 seconds of run time. I let it set for about 30 seconds then try again and it will run for 20 or 30 seconds then die. I let it set again for another minute or so then on the third try it usually starts and runs on three cylinders for a few minutes pushing huge amounts of gray smoke out the tailpipe. Sometimes if it doesn't kick over to all six cylinders, I will let it run a minute or two with the heavy smoke and then turn off the engine and let it set for several minutes. When I restart it will generally switch over to all six cylinders quickly and stop smoking. In the 20's it will also smoke when starting down the road until the engine temps reach normal running level of 165 to 170. As it warms up, the smoke stops.

Detroits are cold blooded but I have never had it fail to start at temps as low as 7 degrees and I never need the boost switch. It just takes a little TLC, patience and a true hatred of mosquitoes (Lots of Gray Smoke).

Re: Boost switch

Reply #20 – December 10, 2014, 07:26:29 pm

I know this conversation is around boost switches and strong batteries but lets not forget the fuel pump. An electric fuel pump can make starting a breeze in cold weather.

Re: Boost switch

Reply #21 – December 15, 2014, 07:33:14 am

Thanks for all the great info! Still would like to know where it is?

Re: Boost switch

Reply #22 – December 15, 2014, 07:52:34 am

Kent, the block heater was replaced not all that long ago. It is usually easier to turn the block heater on before we go to bed than to wait until later in the day to leave so the block heater can have a few hours to work.

Philtravel, I assume that yours isn't by the isolator?

Re: Boost switch

Reply #23 – December 15, 2014, 09:53:49 am

Quote

Still would like to know where it is?

It should be under the bed attached to a board on the front wall. Here's a photo of mine on the 95. Yours will look similar to this. The second photo is of our 99.

Also, Barry's post above links to several boost switch threads.
jor

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