C500 on 3800 swap (Page 1/1)
TXGOOD SEP 29, 06:49 AM
When changing the pin position on my C500 plug for the neutral switch wire I noticed that the Black
wire in A2 had broken loose from the plug. From looking at a diagram it looks like this is a ground wire.
If that wire is disconnected will some accessory or switch just not work or will it cause the car to not start at all?
Thanks

Also, if I`m going to just run the ground to the body or the block would I run the plug side to ground or the fixed C500 block to the ground?

[This message has been edited by TXGOOD (edited 09-29-2021).]

olejoedad SEP 29, 08:33 AM
You need to fix the ground at C500 A-2 and attach it to the engine block.
TXGOOD SEP 29, 09:08 AM
Can I just ground the wire that is in the harness plug or do I need to ground the wire that is on the part of the C500 that attaches to the car?
TXGOOD SEP 30, 07:07 AM
Ok, I got the car to crank. It seems when someone switched over from the original manual trans in the car to an automatic
instead of moving the pin in the C500 to A4 for the wire running to the neutral switch they just reconfigured the wires closer
to the neutral switch.
My problem now is that the car won`t start.
Per this diagram there is suppose to be a Pink wire running from the C500 to the ICM for a 12V feed.
My harness, which is an Ignition Technologies, does not have a Pink wire in the harness from the C500
It does have these two small circuit boards (one which is fried) in the vicinity of the C203 plug.
They are labelled vats.
On other social media sites nobody seems to know what the small circuit boards are, leading me
to believe that nowadays most people just program the vats off in the computer and maybe those
circuit boards aren`t necessary.
And, since there seems to be no 12V feed wire for the ICM in the C500 harness it must originate from
somewhere else.
I just need to get 12V to the ICM somehow and was looking for ideas.
Thanks
Frenchrafe OCT 04, 03:26 PM
Hi,
I recently redid all my 3800 engine harness and I can confirm that mine has a +ve that once ran the original ignition to run the ICM.
If not, then just add a fused +ve wire thats "hot" when the ignition switch is "on". The 3800 ICM takes less current than the original 2.8 ignition circuit, so a 10A fuse is more than enough.
It's strange that the body harness side of the C500 hasn't got the feed? Just bring the feed in from somewhere else, like through the firewall square block.

Regards,
Rafe

------------------
"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France!
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg

olejoedad OCT 05, 12:58 AM
The OEM Fiero harness brought battery power from the Battery Junction Terminal under the C-500 (and through the firewall passthrough) and Ignition ON power from the C203 connector.

To clear the Fiero ECU the battery power was disconnected via a connector on the power wire in the engine compartment.
TXGOOD OCT 05, 08:51 AM
Thanks guys, I finally got it started.
Had to clean the injectors because that engine had sat up for a number of years and 3 of them were completely clogged.
I was wondering something about the charging though.
I have not checked yet to see what the voltage is at the battery but my gauge is reading almost into the Red.
I thought I read somewhere about wiring the alternator up a couple of different ways where either it is controlled
by the computer or some other way but I don`t remember.
My harness had a Red wire that hooked up to the post on the alternator.
I did run an additional wire from the post on the alternator to the junction under the
C500 and then on to the positive of the solenoid.
Should that operate correctly or did I cause a problem down the road.
Thanks