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1973 Jeep Electrical Issue
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Trey73
New User
Jan 13, 2016, 3:37 PM
Post #1 of 5
(1562 views)
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1973 Jeep Electrical Issue
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Hello All. I'm trying to solve a frustrating electrical problem with my 1973 CJ5. The jeep has been modified with the following upgrades - Howell TBI installed on the original 258 - basically an early 90's Chevy 4.3L injector and computer. Recently installed LED lights on everything except the headlights and installed a set of speed hut gauges.
The headlights, tail lights and dash (speed hut) lights all pulsate at a frequency of about 2-3/second while at idle and it appears to get quicker with RPMs. The lights do not turn off, they simply pulse in brightness.
I've tested the battery and alternator - both are a little low. With a load, the alternator is putting out 13.3 volts. A cold battery is a little over 12 volts.
I did a diode test across the alternator and the multimeter didn't show any reading change when I swapped the leads around. The alternator wiring was disconnected, but it was still grounded to the engine. I didn't get a reading from my meter, so I don't know if it failed the test or if it was just a poor test procedure (me!)
Any ideas on what could be going on? It is embarrassing to drive at night as the lights sort of "flash", but I'm more worried about potential damage to electronics with this going on.
More Details -
The lights do not shut off all the way. They pulsate. The pulses can be seen on the dash voltmeter. I turned on my KC lights, which are not part of the main harness and operate off of a relay that is directly wired to the battery, both terminals, so no possibility of a short or poor ground - a very simple circuit. Sure enough, it starts pulsating. Turned on the heater, more pulsating, turned on the headlights and more pulsating. What was interesting is that the pulses became slower, but of a higher magnitude. What I mean by this is that with a low load, it pulsed frequently, but the voltage was swinging only +/- .5V. With the high load, the pulse was +/- 1V but the frequency decreased.
With the engine not running everything is nice and stable, but obviously a drain on the battery. I'm almost convinced this is an issue with the alternator, voltage regulator (which was replaced by a shop recently, but I've read some of them can be junk), or the battery. With different circuits creating similar problems, the commonality begins at the battery. I recently had a failed battery on a motorcycle and it did some crazy, crazy things right as it failed. This thing starts like a champ though and shows 12 volts.
Also, I have a very high end stereo and amp on the jeep and it is not impacted by this, which surprises me. The installer may have put filters in the lines to keep this sort of thing out. I've got quite a bit more pulling on the system than the original jeep ever did - EFI, stereo, auxiliary lights, but I'm still running the same little alternator. Could this possibly be part of the problem?
I think it may be the voltage regulator, but the only thing that keeps me from putting a new one in is that it was just replaced. I brought the jeep to a shop for some fabrication work and the alternator wasn't charging at all, so they replaced the voltage regulator while it was in there. They also had to install a new ignition wire - I can't figure out why that was needed, but I can't see the harm in it either. Also, they had to reground the tail lights (I've got a fiberglass body), but I think that is because they probably disconnected it while doing the fabrication work and they just didn't notice it. The sweeping, load dependent fluctuations in voltage would lead me to think this is the problem.
I appreciate any help or advice you can offer.
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kev2
Veteran
Jan 13, 2016, 4:23 PM
Post #2 of 5
(1552 views)
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Re: 1973 Jeep Electrical Issue
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stock is best -
LED's can be problematic - and this is a common issue,
Lets try this first - how do lights appear with KOEO? Suspect they are fine no issues, YES?
There are several devices to correct the flickering - I will find the info and post it.
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Trey73
New User
Jan 13, 2016, 4:40 PM
Post #3 of 5
(1545 views)
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Re: 1973 Jeep Electrical Issue
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I'm not familiar with KOEO.
Key On, Engine Off? If so, everything is stable when running just on battery.
I really don't think this is associated with the LED's. The headlights, KC lights and heater fan all contribute to the pulsing. None of those are LED.
Also, I can clearly see a pulsing on the voltmeter with no lights on. Unless the LEDs are creating some sort of loop that is messing up the whole electrical system, it is much more pervasive than just the LED lights. Even with some sort of loop, the KC lights are on a separate circuit all together and it is still happening with just that load.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 14, 2016, 2:30 AM
Post #4 of 5
(1528 views)
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Re: 1973 Jeep Electrical Issue
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KOEO = Key On Engine Off.
Hey - This thing is probably such a rat's nest of wires and non OE all over it there isn't too much to go on for me anyway. This age being a Jeep in particular you could easily put an all fiberglass body on the frame which is going to make a grounding issue for about all electrical anything. IMO most would rely on the steel chassis for ground instead of body metal or if metal it still needs to be grounded to engine block and again at body parts as needed for anything to work.
BTW - 13.3V if engine was running is fine and 12V engine off reading of a battery isn't too low yet to blame it or charging system yet or call it a problem yet.
You have flickering anything in this creation I'd be checking that whatever item has good ground and test backwards powering your test light or meter and watch it at what should be steady ground you'll find it. You can add braided ground straps or clean up existing ones that are not known good,
T
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kev2
Veteran
Jan 14, 2016, 9:43 AM
Post #5 of 5
(1509 views)
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Re: 1973 Jeep Electrical Issue
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SORRY- I found it BUT it will need you to add resistor to each lamp circuit - too costly and work intense.
Only suggestion other than STOCK- contact the aftermarket bulb suppliers, see if they have recommendations. Newer electrical systems are designed for LED retrofitting to LED's create the problem - hopefully someone has a package solution other than costly upgrades.
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