Tacho problem with electronic ignition - but NOT bouncing.
7 posts
• Page 1 of 1
Post by: Johnfm » Thu Nov 14, 2013 10:42 am
Got car started last night after replacing points with Accuspark black box and ignition and repalcing dynamo with dynamator.
Not getting any tach bouncing, but I noticed that when I switched on the headlights, the tacho was definitely under reading.
The pulse feeding the tacho is the switched wire that goes form ignition, through the tacho and then on to the +ve coil terminal. It is providing the power for ignition.
If lighting load is affecting the current flow through this wire, will it in fact affect my ignition?
Not getting any tach bouncing, but I noticed that when I switched on the headlights, the tacho was definitely under reading.
The pulse feeding the tacho is the switched wire that goes form ignition, through the tacho and then on to the +ve coil terminal. It is providing the power for ignition.
If lighting load is affecting the current flow through this wire, will it in fact affect my ignition?
1967 Plus 2 #0168
- Johnfm
- Third Gear
- Posts: 333
- Joined: 20 Jan 2013
Post by: rgh0 » Thu Nov 14, 2013 11:18 am
The tach has a 12V supply to it behind the dash and a voltage regulator in its circuits to feed the electronics a constant voltage. it sounds like this voltage is dropping when the lights are turned on and this is dropping sufficiently to overcome the tach voltage regulator and affect the tach accuracy.
I presume you have powered your electronic ignition not off the positive supply to the oil and the headlight wiring is standard.
cheers
Rohan
I presume you have powered your electronic ignition not off the positive supply to the oil and the headlight wiring is standard.
cheers
Rohan
-
rgh0 - Coveted Fifth Gear
- Posts: 8413
- Joined: 22 Sep 2003
Post by: rgh0 » Thu Nov 14, 2013 2:12 pm
this is guaranteed to give you problems --- move it to an independent supply. The electronic ignition takes its power in pulses just like the coil for the ignition and the tach has a tendency to sense both
This is why everyone wastes money converting their tachs as they do the wiring like you have when they don't need to
cheers
Rohan
This is why everyone wastes money converting their tachs as they do the wiring like you have when they don't need to
cheers
Rohan
-
rgh0 - Coveted Fifth Gear
- Posts: 8413
- Joined: 22 Sep 2003
Post by: billwill » Thu Nov 14, 2013 6:05 pm
Johnfm wrote:Will do!
No reason I can't find a switched power source elsewhere in the engine bay or inside the car.
Cheers
Wires powered through the ignition switch are generaly WHITE.
You can make a T-joint to the wire from the ignition switch , BEFORE it goes into the tacho loop.
Bill Williams
36/6725 S3 Coupe OGU108E Yellow over Black.
36/6725 S3 Coupe OGU108E Yellow over Black.
- billwill
- Coveted Fifth Gear
- Posts: 4417
- Joined: 19 Apr 2008
Post by: Johnfm » Fri Nov 15, 2013 10:34 am
All is good.
The tach was only dropping if I switched the panel lights on (not the headlights), but that isn't happenibng now.
I will rewire teh ignition feed anyway, but all is good.
Need to replace water temp sender (as it seems to over read and is a bit inconsistent).
Other than that - these engines love revs!!!
The tach was only dropping if I switched the panel lights on (not the headlights), but that isn't happenibng now.
I will rewire teh ignition feed anyway, but all is good.
Need to replace water temp sender (as it seems to over read and is a bit inconsistent).
Other than that - these engines love revs!!!
1967 Plus 2 #0168
- Johnfm
- Third Gear
- Posts: 333
- Joined: 20 Jan 2013
7 posts
• Page 1 of 1
Total Online:
Users browsing this forum: No registered users and 36 guests
Site map
SitemapIndex
RSS Feed