I’ve been running with the Hall effect trigger board for decades so it’s strange that I should have this question now, but it’s a matter of curiosity. Here goes…
According to Bywater’s explanation, the Hall board needs Ignition 12v. I do remember attaching the “4th wire” from the new board to a wire up near the firewall to pick up the 12 v, per instructions that came with the Hall effect board, long since lost. Since that time, I’ve made a lot of changes, including installing the Crane XR700 ignition system, and at some point a new relay to provide battery voltage to the ignition system when the ignition key is in the Run position. The upshot is I don’t really know where the 12v was coming from in the original installation.
Now, to the present. I had an ignition failure that caused me to dissemble everything for diagnostics and am now in the process of installing a new optical trigger for the Crane system. In the process, I noticed that I have the 12v for the Hall effect trigger board coming directly from the battery! That seemed a bit strange… why would I need power to the trigger board while the car’s parked in the garage, for example?
The answer I’ve come to is there seems no other place that would also provide 12V to the trigger board while the ignition key is in the Start position! This is so because the HE ballast resistor pack has two 12v inputs, one from the Run position wire, the other from the Start position wire. So, if I pick up the trigger board 12v from one, it isn’t available when the key is in the other position. I realize that one could connect it to both with diodes in each to prevent back-feed, but I’ve never seen this described anywhere.
Since it’s been working for years, I intend to continue using BAT +12, but it still seems not quite right.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
3
I believe that the 12V power to the RUN terminal on the ballast resistor pack is powered whenever the ignition is on, including when starting. Power to the START terminal bypasses the ballast resistor for ignition, but that doesn’t mean it’s not there.
I personally wouldn’t think powering from the coil + would be a good idea. First off, the voltage there is reduced by the resistance in the ballast. Second, it’s an additional load on the ballast.
Kirby, the circuit diagrams in the ROM show the Start terminal on the inputs side of the resistor pack connects to the starter relay, whereas the Run terminal connects to the ignition switch (perhaps though the ignition protection relay).
Inside the pack are two resistors in series, 1 Ohm and 1.1 Ohm. The Run contact current goes through both resistors (totaling about 2.1 Ohms), while in Start it goes only through the 1.1 Ohm resistor.
The upshot is if I connect the trigger board to the Run terminal the voltage to the trigger board is 12 - 1A, where A is the Amperage drawn by the board. If I connect it to the Coil+ it sees 12 - 2.1A. If I connect it directly to BAT, it sees 12. My guess is the trigger board would be happy regardless.
But, before I go to the trouble of rewiring things, what’s the down side of connecting directly to BAT? My guess is there is no current flowing through the board if the rotor isn’t spinning.
Why don’t you measure the current to the trigger board and let us know? I’m
betting it pulls current all the time.
Mike Eck
New Jersey, USA www.jaguarclock.com
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2
But, before I go to the trouble of rewiring things, what’s the down side of
connecting directly to BAT? My guess is there is no current flowing through
the board if the rotor isn’t spinning.
Ed
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
7
This is on an engine originally fitted with the Opus? Updating to the Crane XR3000 gets rid of the ballast resistor? Does it also include a new ignition coil, or are you using the OEM coil that worked with the Opus?
So, originally the “Run” contact from the ignition switch energized the “Run” contact on the ballast resistor, and from there on to the coil +. The “Start” contact from the ignition switch goes to the starter relay. A contact from the starter relay goes directly to coil +, effectively bypassing the ballast resistor while the starter is engaged. But when you installed the XR3000, you did away with the ballast resistor and connected the lead from “Run” on the ignition switch directly to the coil +? The lead from the starter relay to coil + could be removed at that point.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
8
A ballast resistor on the start circuit? Interesting. I wonder why.
I certainly wouldn’t leave the trigger board hot when the car is parked. It might not pull significant current, but it just seems wrong.
There are several things that MUST be powered up for the car to start. The EFI system for example. Whatever wire goes to energize the EFI system could also power the Hall Effect trigger board.
Thanks, Mike. Good o hear from you. I’ll see if I can do that tomorrow.
But let me ask another question. Today I wanted to test the pieces before reassembly. The XR70 correctly blinked the test LED when I momentarily short the Crane specified leads to the control module. But I went further and connected the new optical sensor to the module hoping to make it blink when I passed the shutter disk between the light and the photocell. I got a blink, which was good. Then, for good measure, I did it again. Strangely, that seems to have locked the sensor into “always on.” IOW, now whenever I plug the sensor into module the LED is ON… no blinking. So, the question is will this situation be resolved automatically when I put it all back together and the shutter is rotating and sending the expected sequence of light/no-light to the module?
Ed
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
14
Just got off the phone with CompCams.com in Shelby, Tenn., which is who answers the phone at www.fuelairspark.com (aka FAST), apparently the current “owner” of Crane ignition systems. He told me that tests like that “have to be done carefully,” and said he’d send me a return authorization number and get me a new part if it doesn’t work. Very nice of then, considering I bought it from Summit Racing.
Going that way will delay my project of a week or more, so I might just put it in and see if it works before sending it back.
Mike,
In order to get a guesstimate before connecting the DVM for trigger board current draw measurement, I set the DVM to Resistance. I connected one lead to ground and the other to the board power lead, i.e., the “fourth wire” of the Hall Effect board. To my surprise, there is no connectivity!
What am I missing?
Ed
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
18
That would be a valid test if you were measuring a resistance, such as a
light bulb or a coil. It will not work to measure anything electronic, such
as an LED or a phototransistor.
Mike Eck
New Jersey, USA www.jaguarclock.com
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2
