Compu-Tronix Ignition (ver 1)

[phaetn]

Mark, or anyone else, maybe you can help me out with this one.

I noticed the other day that the Compu-Tronix distrubutorless ignition's LED isn't wasn't lighting red when the engine was running. It also didn't run solid red when ignition was on without engine running. The manual indicates this is when it's not getting 12v.

I used a voltmeter to check battery and charging (no light is warning on the dash). Alternator post shows 14.5v (I also know it's good because I had it bench checked professionally earlier this year when getting a new pulley). Battery when engine running, lights on, rad fan on, iphone charging, radio on, shows 14.5v. So appropriate power is getting there. Now the question is is it getting out?

Checked the red lead to the Compu-Tronix with ignition on (engine not running) and it showed 12.3v so that's good, yet the LED still wasn't lighting.

After letting the battery sit overnight on its own it showed 12.8v, so it's holding its charge; however, when I put a trickle charger on it the device quickly went to about 80% charged, but then took a good long while to get to what it indicated as fully charged. Once it did show fully charged the Compu-Tronix led DID show red.

But then after about 15 minutes of driving it didn't flash any more. I had also noticed that sometimes the rad fan would stay on and not shut off. I tried tapping the relay in case it was sticky, but not the issue. Yet other times it seems fine and will turn off. I could envision a situation because of low power issues electrically that the relay gets "stuck on" and then the fan being on just sucks more and more juice from the battery.

Any ideas? The battery is new within the past two years. Should I go and get it load tested? I had funky alternator charging for a couple of years because of a grooved pulley letting the belt slip, could that have affected the battery's chemical balance somehow? Anything else to look for? Odd that my voltmeter shows thinks okay but then the trickle charger and LED seem to indicate less than a full charge.

Thanks for any advice and cheers,
phaetn

[AndyVAS]

Sounds like an issue with the unit. I would email Compu-Tronix because after all, they are the ones that designed and built them.

[zachmac]

Phaetn, when the computronix unit LED quits flashing is the car still running okay? Also, the fan should run after ignition is off until the radiator thermo switch sees cooler temps. If wired correctly the relay is NOT SWITCHED.

AndyVAS: We know who makes them AND who sells them after having worked with the manufacturer to adapt the unit to our cars. Subtle swipes at competitors are not appreciated or helpful.

[phaetn]

Thanks, gents.

Oddly, the car still seems to run okay. Starts fine, idles fine, okay under power. It's definitely getting spark. It was a bit rough the other day, but that may have been heat-related.

Ever since I have had my car the fan turns off when I turn off ignition. Not sure if that's a 1974 thing or PO wiring (it has had mods like brown wire fix, relay for halogen lights). That said if I turn off car with fan running, the fan will not turn on again next time I go to start the car if it has cooled (so temp switch must trigger relay to open circuit as I go to turn key).

Methinks it might be a battery or wiring issue as if I recharge the battery the Compu-Tronix light goes on okay; also turn signal indicator in dash is more brightly liit; also fan will go on and off correctly. But if fan is not turning off, then I would imagine it's drawing a lot of power and the battery just can't keep up.

I don't think my voltmeter is bad, but I wonder if there's something else amiss. Even when my battery was getting drained before from a loose ground terminal at the post the module on the ignition unit would always still light.

Cheers,
phaetn

[RRoller123]

The fan is always wired hot, so it should keep running after you shut off the car until the radiator temp cools below the temp switch trip point. It would only be extremely rare coincidence if this is at the same time that you turn off the engine, and more than once! So for some reason the PO has probably done some wiring fiddly.

That Light Blue wire coming off of fuse block position 10, going to the 2-pin connector at the fan itself, should be always hot at the fan motor, the switch just gives it a path to ground, so it can run at any time. This wiring is for an '80 car, but I would be shocked if the fan circuit is any different for the '74?

[phaetn]

Thanks, RRoller123. Again I'm not sure if it's a wiring mod or if the '74 was different. I have a sneaking suspension it might be, but I don't remember why or where I read that it might be.

Anyhow, the car is an enigma.

I went for a short drive to run an errand. Popped the hood just to see what's what as I parked at my destination.

Lo and behold, the light was flashing! Hallelujah! This was very surprising as I hadn't charged the battery at all overnight and yet it wasn't flashing yesterday. Waited for the fan to cycle on. It did, light still flashed. Waited for fan to turn off (quite a wait) and it did. Light still flashing. Yay!

Turned off the car. Went and performed errand.

Back in car after starting fan didn't turn on because temp was cool enough without it. Drove not more than 5 minutes to my next errand, which didn't involve any stop lights or even signs so it kept running cool. At my next stop, popped the hood. No flashing light. ARGHHH! What had changed? Ignition switch on and off. Can't think of anything else. Waited a minute with stopped car and fan came on.

After second errand drove home and flashing light never came on. At home, with fan on, it was taking a long time to turn off but a laser temp shows pretty good rad temps (~90°C top right corner of rad, down to about 78°C at the bottom).

I wonder if I have an issue with the fan so it's drawing too much from the battery. I dunno. I will have battery tested tomorrow and go from there...

Cheers,
phaetn

[RRoller123]

Is you Compu in the distributor or block position? If it is in the Distributor position, it may be overheating. I put mine in the block position (which involves a little work for the alternator bracket but not too big a deal) and it has never caused any trouble in 4 years I think it is now. The heat may be causing an intermittent of some sort with the led circuit.

[phaetn]

Thanks for reply. It's in the block.

Pattern repeated today: lit with ignition on, stayed working for about 10 mins, then not lighting.

Flasher has been a bit wonky, too: dash light turn signal almost needs to "warm up" before consistenty lighting strongly.

Will get battery checked and go from there. It may somehow have been chemically damaged from past alternator issues.

Thanks again and cheers,
phaetn

[phaetn]

Update: pulled the battery. Cdn Tire had some quick test that showed it was okay with a printout. I asked them to deep cycle it and left it for a couple of hours.

When ready they did another quick test that largely showed same results. While I was at it I also put on a new turn signal flasher.

Things are working better now: igntion light is illuminating, lights on dash are much brighter for turn signal, fan coming and and off okay.

Not sure if it's a better charged battery (I'll keep my on it) or if a flasher that was on the way out was somehow interrupting a circuit and caused cascading problems. I suspect the former...

Anyhow, thanks again.

Cheers,
phaetn

[phaetn]

And now it's not flashing again after a short drive. <shrug>

I think I'll stop worrying about it as I don't want to borrow trouble ahead of a drive to Montreal next weekend to an Italian car show. It's a 500km round trip so I'll just keep my fingers crossed.

Cheers,
phaetn

[seabeelt]

I have had two of them fail. First one was a first gen and I got about 3k miles out of it before it faulted (and I believe caused the backfire and resultant carb fire) not pointing fingers but seems logical) Second unit was a 2nd Gen (shorter than the first) and ran all of 10 minutes before it faulted (with backfire and fortunately no carb fire this time) Both units were block installations. I must say the 2nd Gen unit was much much easier to install ( with a little modification to the hold down bracket (no removing the intake manifold either)) Wiring could not be easier. Power from the switch - in my case blue wire with black stripe and brown wire to the tach. That's it! Disappointingly, I don't think I will try a third. For reference, battery is newish (3 yrs old, running 95 Amp alt and have good voltage all around) Back to the points for me (just rebuilt/replaced the bearings and oil seal so it doesn't drip on the exhaust manifold)

[architect]

Did you plug the vacuum advanced on your carb? I just installed the Computronix system and a Weber 32/36... no where to run the hose?

[phaetn]

Heya - not sure if this is helpful or not. I have an EMPI 32/36 DFEV (electric choke).

Not sure about the vacuum advance. I don't know if it's already capped or what on the carb -- I only have one hose out from it and it runs the top of the charcoal canister. No other outlet/inlet that I can see (apart from fuel, of course!)

My intake manifold, meanwhile, has brake booster hose on one side of the T outlet (large diameter), and on the other side (smaller diameter) I have capped it with a small section of hose with a clamped bolt as a plug.

Cheers,
phaetn

[architect]

Did you plug the vacuum advanced on your carb? I just installed the Computronix system and a Weber 32/36... no where to run the hose?

Per Mark, just plug or run to the crankcase