Community Forums

Terry W · 09-03-2016, 09:42 AM

I am wondering if the battery boost switch on the dash is supposed to tie the batts together through the Trombetta solenoid or does it do it behind the scenes? Also does it ground the solenoid causing it to close?

When I push the boost button nothing appears to happen. This isn't a huge deal but I'd like to know how it's supposed to work so that I can add it to my list of little things to tinker with

Thanks, Terry

Old Scout · 09-03-2016, 10:58 AM

On my pre-Vansco 03, its a direct connect to the solenoid--probably a ground switch as the solenoid is powered at the battery cable connection. After 04, the circuit is likely controlled by/thru a Vansco circuit--overrides the Vansco logic that controls the normal battery bank charging. Believe earlier Alpines have a momentary switch which requires you to hold down the switch for boost function, while newer Alpines have an on/off switch so boost can be left on if needed.

Ken T. · 09-03-2016, 11:10 AM

On my 2005, pressing the button sends a signal to the Vasco unit. On the Vasco unit #19 lights and the solenoid energizes.

Barbaraok · 09-03-2016, 02:36 PM

Why would you 'tinker' with it. I have used it when we weren't getting enough 'juice' from the chassis batteries to start the engine. Worked just fine and then got the problem with chassis batteries fixed.

wolfe10 · 09-03-2016, 03:38 PM

David,

Two schools of thought here:

1. Exactly as you said-- emergency use only.

2. Because the smaller the voltage drop under extreme high load (starter on 8.3-8.9 liter diesel) the better is the intake manifold heater and starter. So, many of us use the boost switch all the time when starting. Said another way you can not have too many amp available to that large starter.

Old Scout · 09-03-2016, 06:50 PM

Wow--never thought about using the boost in cold weather to help with the grid heaters. Disconnected the boost solenoid 10 years ago--never missed it--guess I need to think about reconnecting it. On the other hand--maybe that's why I live in south Texas....[smile]

mel s · 09-03-2016, 07:01 PM

Quote:

Originally Posted by wolfe10

David,

Two schools of thought here:

1. Exactly as you said-- emergency use only.

2. Because the smaller the voltage drop under extreme high load (starter on 8.3-8.9 liter diesel) the better is the intake manifold heater and starter. So, many of us use the boost switch all the time when starting. Said another way you can not have too many amp available to that large starter.

Brett
What is the correct procedure for using the boost switch in an emergency?
Does that procedure differ from using it all the time when starting?....If so how?
Thanks.
Mel
'96 Safari

wolfe10 · 09-03-2016, 07:58 PM

Procedure is the same-- just a matter of if it is only used when the chassis batteries alone will not start it or every start.

Procedure:

Hit the boost switch BEFORE turning on the key (do not close a relay/solenoid under heavy load-- it burns the points).

Turn key, intake manifold heater, start.

Only after engine is running (and if very cold after the intake manifold heater is off) do you turn it off. Again same reason, do not open contacts under heavy load.

mel s · 09-04-2016, 06:13 AM

Quote:

Originally Posted by wolfe10

Procedure is the same-- just a matter of if it is only used when the chassis batteries alone will not start it or every start.

Procedure:

Hit the boost switch BEFORE turning on the key (do not close a relay/solenoid under heavy load-- it burns the points).

Turn key, intake manifold heater, start.

Only after engine is running (and if very cold after the intake manifold heater is off) do you turn it off. Again same reason, do not open contacts under heavy load.

Thanks.

Mel

Janet and Todd · 09-04-2016, 10:51 AM

Have someone work the switch with the key on while you stand by the battery bay and listen to the Trombetta click in.

YC1 · 09-04-2016, 11:27 AM

Grab a simple 12 volt test light or better yet a meter. See if either of the little posts cause the light to glow with the switch on and then off. If the light comes on and off with the switch it is being controlled by voltage and not a ground.

Once you have done that you really need a voltmeter to check each of the large posts with the solenoid engaged. The voltage should be the same. You can get fooled if both battery banks are fully charged so holding the boost button down while starting should show the same voltage on each large post if it is working ok.

Those relays are a common failure item.

Terry W · 09-04-2016, 08:14 PM

Quote:

Originally Posted by Barbaraok

Why would you 'tinker' with it. I have used it when we weren't getting enough 'juice' from the chassis batteries to start the engine. Worked just fine and then got the problem with chassis batteries fixed.

Cuz it ain't doin nuttin!

Terry W · 09-04-2016, 08:20 PM

I took a hard look at the VMM sheets and I'll do a little more poking around tomorrow. It looks like the close signal isn't getting from the boost button to the solenoid.

I believe input 15 should light when the boost is used and signal 19 to close the solenoid to tie the batts together. I'll see if 15 is getting the signal from the boost switch.

Thanks, Terry

kerryvan · 09-04-2016, 08:59 PM

Quote:

Originally Posted by Terry W

Alpine Coach........That's how Jaguar would've done it!

could this be Lucas electrical way of doing things? I always thought Lucas was the only bad way of doing electronics, from my Jaguar friends who were part time owners of their xke, the shop owned it 70% of the time....