1 HDTfte electrical Question

Submitted: Tuesday, Oct 06, 2015 at 21:55
ThreadID: 130527 Views:1428 Replies:3 FollowUps:6
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I just bought a 2nd tray (to install 2nd battery under bonnet 79 series 2006 ), when I uninstalled the computer & a round thing (Both still plugged in) the motor would start. I bolted them both back in & it started. Is this a grounding issue? if so with the computer or the round thing?
Nothing added yet as I ran out of light.
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Reply By: Ross M - Tuesday, Oct 06, 2015 at 22:09

Tuesday, Oct 06, 2015 at 22:09
A bit confusing Kevin!
You said "
"when I uninstalled the computer & a round thing (Both still plugged in) the motor would start."
Then you said it still will start with them bolted back in?

Do you mean in the first instance the engine DIDN'T start?
If so, many items rely on a negative connection to make the circuitry work, ie, to complete a circuit, so yes very probably it does need a negative connection.
AnswerID: 591279

Follow Up By: Kevin P7 - Friday, Oct 09, 2015 at 00:28

Friday, Oct 09, 2015 at 00:28
OK sorry I couldn't edit the text, I found out it was the computer grounding, but as yet I haven't got my new battery holder in yet, very tight space & some stiff wires
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FollowupID: 859430

Reply By: pop2jocem - Tuesday, Oct 06, 2015 at 22:59

Tuesday, Oct 06, 2015 at 22:59
Sorry mate maybe I am missing something here. What exactly is the problem?
AnswerID: 591283

Follow Up By: Kevin P7 - Friday, Oct 09, 2015 at 00:29

Friday, Oct 09, 2015 at 00:29
I've found it to be a grounding issue
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FollowupID: 859431

Reply By: Member - Phil G (SA) - Wednesday, Oct 07, 2015 at 20:55

Wednesday, Oct 07, 2015 at 20:55
Kevin,
it is critical that that black box (something to do with the ECU) is well earthed. The instructions that come with the battery tray should have spelled that out. If it's not earthed, you can fry the ECU. Many instances of this happening soon after the HDJ 70 series was released. I ran a separate earth lead from the housing to be sure. I had an ARB tray and it was supplied with many star washers to ensure the tray was well earthed, as the black box was mounted to the tray.
AnswerID: 591326

Follow Up By: Member - Phil G (SA) - Wednesday, Oct 07, 2015 at 20:56

Wednesday, Oct 07, 2015 at 20:56
Just to add that the round thing is just a connector for the preheat circuit from memory so grounding is not required. But the black box is the critical bit.
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FollowupID: 859389

Follow Up By: Kevin P7 - Friday, Oct 09, 2015 at 00:39

Friday, Oct 09, 2015 at 00:39
Thanks Phil, yes it was a grounding issue with the CPU. At first I thought I was up for an auto sparkie.

I bought the battery tray from a wrecker of a 78 series ($70) (rear position) (said to be off a 24 volt cruiser).

As yet I have found it very tight & may need to move some wires. So I put everything back & have just lost 2 hours of time.

I'm still not sure if this tray will fit.
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FollowupID: 859433

Follow Up By: Member - Phil G (SA) - Friday, Oct 09, 2015 at 09:09

Friday, Oct 09, 2015 at 09:09
Yeah, not a lot of space in there. The 75series (pre 1999) trays did not fit the 78/79series because of a subtle change in the design of the front end. But if it genuinely is a 78series tray, it should go - the black box and round thing are usually relocated to a bracket attached to the front of the tray. I'd run an extra earth lead from the body of the black box to the body - just above where the air cond pipes go thru the firewall.
The "wire that won't move" - can't quite remember, but thought it usually sits in the small gap under the tray.
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FollowupID: 859435

Follow Up By: Kevin P7 - Saturday, Oct 10, 2015 at 13:51

Saturday, Oct 10, 2015 at 13:51
Thanks Phil, I'll keep trying.
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FollowupID: 859482

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