Intermittent sudden lack of electrical

[pdubu]

Okay, can't find anything searching the archives but that doesn't mean it hasn't been addressed before.

Vehicle: 1990 Colony Park LS
Symptom: Intermittent sudden loss of electrical power

Driving along after for about 15 minutes, I slow to a stop to wait for an "Wide load" to cross the local bridge. Radios going, fan blowing, engine purring. Suddenly it is like someone puled the plug. No engine, no radio. no fan, no power to anything. A few people help me push it off to the side and during the push the radio comes on for a couple seconds then off.

I poke around and find the negative cable is loose, wiggle it back down as I don't have any tools with me, nada. Look at the fuses, all seem okay, jiggle a few odd connectors still nothing. As I contemplate calling AAA, I decide to twist the key and it fires up. Total down time about 10 minutes

Start heading back home to switch rigs and it dies again. Same way, sudden overall loss of electrical power. Wiggle the same things, not luck. Wiggle the positive battery cable and find it is a bit loose. Jam, wiggle it onto the post a bit better. Starts up. Total downtime about 5 minutes.

I started the rig the next day with no problem. Since the only common item other than downtime was wiggling the battery terminals, I crossed my fingers and pulled each battery lead loose for a moment. Engine kept running.

Any ideas? To make it very clear: the main symptom is no electrical of any kind, though some items, dome lights, radio did come on before the starter/ignition would respond.

[86GmLsCoupe]

I'll just start you off some with some suggestions and I'm sure everyone will also help fill in. The first thing I would do is clean the battery terminals off well and make sure the connections are clean and tight. The next possibility that would come to mind for me personally is the ignition switch getting old, coming loose, and having a poor connection but that's just a guess. Oh, and welcome to GMN.

[91waggin]

Exact same thing happened to me awhile back. I'd lose everything except for some minor electrical accessories. Turned out to be a wire with an intermittent open circuit right at the firewall... good old Ford electricals. Check the continuity of all wires that run through the firewall in that one big bundle and do as good of a visual inspection as you can.

[Lincolnmania]

might be the ignition switch

[fordktpjoe]

Same thing happened to me back during the winter...wound up with loose/dirty battery teminal connections, and a touch of corrosion at the solenoid connections too. Don't forget to check those.

[85crownHPP]

ditto on the switch, or bad fuse link at the starter solenoid

[gadget73]

What they said, and do not pull the battery cables while the motor is running. Its very hard on the alternator and its not really good for the ECM either. The alternators in these things are under-rated and use a poor connection system that likes to catch fire under normal circumstances. Stressing it like that is just asking for trouble.

[pdubu]

I was able to replicate the problem even after swapping out the ignition switch and having the panels bolted back in place (and no symptoms) yesterday.

I pulled the panels off to see if I couldn't determine what the connector goes to that I asked about in another thread. It started up with the panels re-removed for that activity, but replicated symptom of only minor electricals and no start power after bolting it back together.

While some would see this as frustrating, I see it a huge help in diagnosis. Now I have it narrowed down to something I could have affected. So tomorrow when I get a chance, I'll open her back up and start wiggling and inspecting wires. Sounds like 91waggin's root cause might be the same here.

A word on diagnosis:
Since I didn't start the car enough to build any real heat today in the engine (maybe 30 seconds total run time today) and the outside temps were stable I could rule out environmental factors playing a part in the problem.

Swapping the ignition switch was a leap of faith and a reasonable "go do" item on the list of possible causes. Sometimes this is the only course of action (and you cross your fingers that the problem disappears.

I had already cleaned and tightened connectors at the battery end. Checked all readily accessible (without unbolting anything) wires, fuses, etc via unplugging or wiggling.

I was hoping it wasn't environmental factors coming into play as it was a warm day (for us in the Northwet) having been there on a Corvette that would conk out intermittently. It had worn pins to the ignitor box from other work on the car. When underhood temps rose the pins acted like bimetallic switches and with the right jostle, would lose connection. Wiggling the connector cold had no affect, but when it was warm you could wiggle the connector and trigger it on and off.

Agreed that pulling battery cables off a running vehicle can risk added problems. What it will tell you though is if you have a really strange problem (corrosion can cause some strange electrical backfeeds) as most engines can run off the alternator for a few. The key to not causing undue havoc to your ECM and regulator is to NOT replace the cable until the motor is back off. There is still a risk, but if you really feel you need to attempt this test, which in my case with both cables loose it was possible they had lost contact anyways, proceed with extreme caution and have all electricals not needed OFF (radio, wiper, windows, lights). Pull the cable and if the motor is still running have a helper turn off the motor within a couple seconds. If it is going to die or give a change in tempo, it will happen FAST. What kills the ECM is a voltage spike when the battery is reconnected while the alternator is already providing power.

[86GmLsCoupe]

Well to bad it wasn't just simply the ignition switch, that would have been nice huh? Good thing is, they are one the main three electrical boogers on these cars, the other two being the 2G alt and headlight switch. You should notice a difference when you turn the key in the ign. switch now that the new one's on, it's not so effortless to turn now so consider it money well spent. In terms of fuses (reg or fusible links), I'd say once it goes it goes, so it's not going to be an intermittent issue. This is kinda a tough one.

[Freshmeat]

Trace your alternator wires to behind the washer reservoir. If you blasted one of the fusible links you can get these exact symptoms. Trace it at least to the connector at the fender well.

[pdubu]

Well I couldn't send her to the crusher (if she was in crummy shape,it would have been a no brainer) without one last try at resurrection. So I made a few hours in my schedule.

I used a wire from a constant hot source to start jumpering items into action and confirming continuity and expected resistance. Relays proved out, as did most of the accessories that weren't working. I eventually traced the problem down to one yellow wire that should have been feeding power forward to quite a few items. I backtracked to the battery from there.

The culprit was found under the window washer tank. Not at the fusible, but at a point where four other wires are joined to a heavy black/orange. The join was heatshrinked that appeared to be about all that was used to hold it together from the factory. A tug of the wire proved out the reason real quick. A quick test by pushing it back together and a light clamp with visegrips (insulated using a piece of hose) showed that was it.

I pulled out my soldering gun and various electrical cleaning products and rejoined it.

All is well now except most of my main wire harness needs to be rewrapped. PITA.

[gadget73]

Oh, the alternator connector. 4 wires, two black/orange, one yellow, and i think one small something else, tan/blue maybe?

[Glen]

The yellow wire would be the main power wire for the car. The orange/black wire is the alt. wire.

[pdubu]

Three black/orange and a yellow. Two larger Blk/Org going to the alt, the smaller blk/org and yellow head to the firewall and relays.

Kind if crazy, since the area didn't look bad. If I hadn't gave a mild tug, I may not have found the break. Freshmeat came pretty close to calling it on the nose as to location.