Piazza overdrive switch wiring

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wrx884
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Piazza overdrive switch wiring

Post by wrx884 » Fri Dec 11, 2015 5:19 pm

trying to work out which wire is the one that's used for the over drive switching solenoid on the piazza auto gear boxes? there's a 2 pin connector on the box with a white and a red wire attached, I'm assuming its one of these but not sure which? one would be for the lock up convertors electronic black box too right?

I just need to know which is the overdrive feed wire, also is the feed to these wires a positive 12V fed for the switch to work or negative switched?

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Post by IZU069 » Sun Dec 13, 2015 8:34 am

Do you have piazzamanual.pdf? (Get it!! See the Home page.)

I can try to check my box(es) and scattered wiring but that might take time (like, maybe next century...).
But based on the PDF wiring diagrams...

p813 (12-79) shows BrR to the grounded O/D Solenoid and Br to the grounded Kick Down switch. (So the solenoid is +12V switched from the OD Computer, and the Kick Down switch is ground switching (negative switched) - both of which are typical wiring conventions (but NOT always!).)
Both go through a 2-terminal spade connector ("D").

That's supported by the wiring diagram foldout Section 9 (p871). (I recently found the detail of the dash wiring to be inaccurate.)

My assumption is that BrR goes to your Red wire.
I would have assumed White was solenoid ground but maybe only case/chassis grounding is used (IMO unusual for Japanese to do but I'm not familiar with the auto's electro-mechanical implementation)...
Hence if the PDF wiring is correct and there's only one 2-pin connector, Br is likely to connect to White.


It should be testable...

A continuity tester (DMM or test light etc) to confirm White grounding when the kick-down is pulled.

Ideally resistance across the solenoid though it may be too low to measure, so +12V to Red BUT ONLY after the White "switch" is confirmed - you don't want +12V across a closed grounded switch (though I'd assume the switch to only be closed when kicked down).
If unsure, DON'T do the +12V test!!


I'll see what I can confirm. I have an auto box outside.
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Post by wrx884 » Sun Dec 13, 2015 11:39 am

So my only choice to get the PDF is to pay for it? I understand it benefits this forum but in the time I have joined up it seemed like this forum has died and nobody has been using it since LOL.

Is the kick down switch the cable itself in the auto box where the cable attaches to or is this different again? I'm trying to source a kick down cable for one of these as we speak but so far it seems they are hard to find or get. Id imagine a lot of the guys that convert to manual would have the auto boxes laying around so there should be some supply of them id imagine?

cheers for the info so far it will help greatly ive gone in the other direction to most and have fitted a piazza auto box to a Gemini purely just the get the 4th gear :) doing this means I don't need the lock up converter box that runs to the ECU normally so just the OD switch solenoid is all I need to get the OD to operate :)

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Post by IZU069 » Sun Dec 13, 2015 4:46 pm

Yeah. $12 for the PDF. It used to be $15. Some sucker scanned 900 pages and converted to PDF for less than 2c a page. He later "donated" the PDF to help fund the Piazza site which cost over $100 a year to host.
I like the PDF because it's more portable and transferable. Sure, it's not searchable (because it is scanned) but essentially I only use a few of the wiring diagrams in its 135 page electrical section (not including the 5-6 multipage foldouts). IMO the foldouts alone are worth $15.

I don't know if this site has moved to faceboob as many others have done. I don't care - I'm not joining faecesbook sites.
Even if this site is dead, IMO it still hosts much information. (Dare I comment on other active sites - albethey other Isuzu or I-GM and not Piazza - that are very much alive but IMHO contain so much rubbish & naive info that they should be banned!)
If this site is dead and useless, maybe I'll suggest to admin they save the money and unhost it.
In the meantime it does get the occasional inquiry which seems to be resolved, but maybe I am fooling myself as to how valuable that assistance is. After all, inquiries should be able to be resolved on other sites or hardcopy manuals etc.

Alas I haven't hit my autobox yet for any perusal. My day has been rudely interrupted with other issues.
I'll try to get to my autobox etc later today.

Though I did have a good grasp on controls like the ECU & OD etc, lack of stimulus has clouded memories.
And other than a few digidash repairs there wasn't much response to digidash upgrades that were likely to include EMS & OD etc functionality, and now that I'm leaving Piazzas...



PS - don't take my comments as a criticism of you, I merely used it as am opportunity to comment on things said by others, and since I never (or rarely) initiate threads...
It also states else reiterates that I am leaving. Once my Piazzas are gone this will become another of my rationalised sites. (Some key people have the means to contact me independent of this site.)
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Post by IZU069 » Sun Dec 13, 2015 6:14 pm

My autobox has Black & Pink wires, the Pink male spade being adjacent to the plug's index.

Pink goes to the switch.

Black is to the solenoid.

Both are easy to see on the left-rear of the box so color confirmation should be easy.

FWIW, the solenoid measured ~16 Ohms so it's <1A. I did apply +12V and it clicked as expected (with batt- aka 0V/GND to the gearbox housing.
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Post by wrx884 » Sun Dec 13, 2015 11:54 pm

thats cool i contacted roy and have paid for the pdf manual if it helps to keep this info and contacts around for the help thats appreciated so i dont mind paying for that :)

cheers for the extra info too it will go along way getting this build finished finally.i'll double check on the wire colours to confirm (box is in a shop being fitted as we speak).

so the solenoid is it actually inside the box already? thats good news if it is should be a simple connection to the OD switch, just need to apply 12V and we should be good to go as far as wiring goes.

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Post by IZU069 » Mon Dec 14, 2015 12:37 am

Yes.
It is a solenoid, not a relay.
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Post by wrx884 » Mon Dec 14, 2015 6:23 pm

Just checked ur right not sure why I thought there was a white wire there but definitely there is one black and one pink (I thought was faded red from its age LOL). this seems like the goer just need to get that kick down cable now.

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Post by IPTOC » Sat Jan 30, 2016 3:51 am

Overdrive module under the dash switches the solenoid on the gearbox.

If your auto box won't shift into overdrive, it could be a kickdown cable setting issue (common after cylinder head work) BUT check that the thermostat is ok and the engine is warming up properly - the overdrive module takes a temperature signal from the ITEC unit and will not allow the 'box to go into overdrive until the engine and 'box have warmed up!!!
1988 Isuzu Piazza HBL Auto - Ebony Black
1988 Isuzu Piazza HBL Manual - Romanesque Silver
1851 Cellar chock full of Isuzu spares!!

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