6BTA Air intake heater grid relays and control box removal

[Alex]

Hi everyone,

I have been troubleshooting a no start issue and noticed that under the starter there’s a bunch of connections to relays and a box with a large plug on it.

My guess its all related to the Air Heater Grid, which have no idea if it works or not as some cables are loose.

Do I need this in the tropics?

How do I disconnect all this and eliminate it?

Does the “box” and large plug on it control any engine start and run essentials to consider?

Thank you!

Regards,
Alex

Topic

[Alex]

J, Exactly what I did. Removed the whole bracket under the starter with the two heater mag switches, the control box and all the wiring related to that and going around the back to the heater grid.

Still in the process of pulling the engines for other maintenance but that’s basically it on the heater.

The other step related to starter maintenance would be to find a location that is more accessible for the starter mag switch. I would like to not have it under the starter and behind the oil drain tube.

Here’s a diagram that may help, from Tony’s Tips…

[J Dragon]

Hi,

I am in New England and he fuse on my grid heater has been pulled since I’ve owned the boat. Boat is hauled for winter months…

I have my heat exchanger and aftercooler off for service, and am tempted to remove the intake heater wiring to simplify things for myself going forward and create some more room if I ever have to swap starter, etc..

It seems like there is no issue doing that? Rob, do you have a pic of the 3rd mag switch and how to deal with it as you mention here:

All you have to do so is remount that third mag switch that is for the starter.

Thanks all!

[Rob Schepis]

Grid Heater

Leave it be. Post some progress and finished pics. That will add great value to this post.

[Alex]

Hi Rob,

I started disassembling the heater solenoids, control box and disconnecting the wiring under the starter side of one engine.

The SBMAR article does not mention if the heater block itself also is removed (in the aftercooler outlet to the engine intake) (block with two cables in the air passage).

What do I do with that piece? Leave it in place but disconnect cables?

Remove it (block) completely which will lower the aftercooler outlet port by about 1.5″?

Thanks

[Alex]

Nice, very clean engines by the way.

Trying to figure out if the coolant feed tubes I ordered will fit my engines. Will probably create another topic for this.

Thanks!

[Rob Schepis]

“Your 6BTAs are installed in what kind of boat?”

1974 Chris Craft 36 Commander Tournament

[Alex]

Thank you Rob,

Correct, I basically need to service aftercoolers, heat exchangers and impellers as a minimum while I’m at it.

I have ordered a bunch of parts from SB and gathering my inventory to do mayor work, even taking gears out to replace shaft seals etc. So as you can imagine Ill be going thru a bunch of systems in the next two months tied up and as with all boat projects it will snowball into a lot more.

Your 6BTAs are installed in what kind of boat?

[Rob Schepis]

“Do I need to remove the aftercooler, intake or turbo itself to remove the heater grid harness that wraps under all that?”

You should not but the aftercooler probably needs servicing anyway… Here’s one of my 6BTA’s with the aftercooler removed so you can see what’s behind it.

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Tony Athens

[Alex]

Thank you Rob.

When I mention some cables are loose its basically on the heater mags switch jumper cable, missing a nut to the terminal stud. My guess is it has not worked for some time and as you’ve said, not needed.

I just bought the boat and Im getting to know it and get all the bugs out.

I will be removing this heater grid harness this week as I also need to replace a starter on that particular engine (starboard) and that will cleanup things.

Since those mag switches are the same Ill keep them as spares for the starter mag/relay. Perhaps even relocate that starter mag/relay higher up on a heat exchanger bolt and bracket for better access in the future.

Do I need to remove the aftercooler, intake or turbo itself to remove the heater grid harness that wraps under all that?

[Rob Schepis]

Not needed, especially in the tropics. These were implemented to minimize start-up smoke and aid in cold starting. They only come on at low rpm (idle and a few hundred rpms over) and only when intake air temp is under a setpoint temp, in the range of 90degF. There is an EMC that is mounted down low on the starboard side of the engines. There are also three identical mag switches) there on the same bracket, two are for the air heaters elements and one is for the starter. They are identical, so remember that as they can be spares for the started mag switch.

“Some cables are loose”….. ???

Obviously when chasing an electrical gremlin the first order of business is to make sure all connections are clean and tight.

You can remove the control fuse for the grid heater setup. It’s tucked in and zipped tied behind the aftercooler. Your start-up voltages should go back to normal, check that. But if yours were never working you might not see a difference. Leave the fuse out. You can remove the entire setup, including the bracket with ECM and mag switches and the harness that plugs into the engine harness. It’s an isolated setup that can be removed without disturbing anything else. All you have to do so is remount that third mag switch that is for the starter. If you want to keep the setup in place you can remove the fuse and wire the control circuit to a switch at the dash. If you search the forum there is a bunch of stuff on the grid heaters.

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