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74 620 PU Ridiculous Voltage drop / ground / engine dying when power is turned on issue!? Saturn GM Alternator Upgrade?


Hmph

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Haha…sorry for the thread title…but seriously, I'm getting my arse handed to me here guys.

Also a genuine apology if this thread is hard to follow. Long day of work and some beers to follow make my posts seem a bit "rambly"…

 

Firstly, I feel like I know my ways around an old car…confident and comfortable with a volt meter…and have had 1st hand experience trouble shooting MANY old (especially j-tin) cars from barn find-to road readiness.

 

Regardless, this is stumping me. Most likely something simple…stupid…but damn.

 

Some maybe pertinent information - 74 620 w/ L20b w/ emissions delete and weber 32/36 DGEV. Otherwise STOCK with stock wiring. 

 

Since I've acquired the car admittedly there's been a butt ton of misdiagnosed electrical issues that I chock up to a bad ground issue…as well as bad contacts on some fuse panel connections. (originally only 1 engine bay ground- negative battery terminal to head  - i've since added block to frame and frame to body)

 

A CS130 GM alternator was sourced and install was completed. Fuse panel was removed, soaked in Vinegar and scrubbed. Sufficient ground connections have been added throughout engine bay… and at this point progress was made! Stuff that did not work before worked now (high beams, hazards) and truck drove fine for a few days…with all electrical working and no issue. 14.8V while running regardless of what elec acces were turned on…(does that seem strange?) 

 

I will also admit that the few times I did drive after the alternator upgrade etc…I would hear a relay behind the radio-ish clicking randomly or intermittently while driving. I later find out that is the heater relay - with electric choke wire that should've been dealt with when the new Alt. was installed. I ignorantly did nothing with this wire.

 

I go for a multi hour drive with no issue - and then (thankfully close to home) truck RANDOMLY dies while just steadily cruising. 

And I'm talking DIES. Nothing functions as far as the key or dash knob is concerned. No illuminated Charge light (which functioned well before) as well as just plain no power to ANYTHING….no starter, no nothing, essentially behind the fuse block. Ignition, as well as lights, signals, hazards etc.

 

I whip out the multi meter and test voltage at battery - good (12.6/8ish when off), alt has power, starter has power, so I head to fuse block.

 

Fuse block has power at a few fuses (I don't remember which and am not familiar to know my trucks layout) only with key in OFF position. 

Once the key is moved to anything other then the off position voltage drops to .2 or .3 V at those fuses that shortly before showed 12.6ish (when key was in "off")...

 

This happens once key is turned to anything OTHER than off. (Acc, on, start)

 

I fiddle around a bit with some relays, ignition switch, and I unplug the heater relay and all symptoms are gone. 

 

The truck starts as should, runs, only until I pull the headlight switch. 

 

Trucks dies immediately - and shows same symptoms as before until I remove battery cables from battery for a good few minutes. 

I can then reconnect the battery - the truck will fire up - and run fine until parking lights or even headlights are turned on. 

 

I then check out the headlight relay - unplug - am able to start the truck and turn on parking lights successfully and everything seems ok until I engage hazard lights. 

 

Truck then dies and is COMPLETELY non responsive until I disconnect the battery and let things "cool off"? for a while...

 

I can now restart the truck…get good voltage readout (14.6-14.8V when running) but it continues to die when any other voltage is introduced …(parking/headlights/hazards…etc)

 

 

 

WTF!? Any ideas? That may not make much sense….but I tried. and am tired. hah!

 

Thanks all.

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Many electrical circuits will show "normal" voltage, until a load is put on them, if the connections are bad.

Clean the battery terminals.  Does a 620 use fuseable links in the wiring harness?  Check those.

Never trust a glass tube fuse.  They can look good, but be bad.

 

Turn the headlights on, or at least try to.   Check for battery voltage at the battery cable.  if good, follow the wires to a fuseable link, if you have them.  check the other side of the fuseable link.  Follow that wire to the fuse box, check voltage there.  Then on the other side of the fuse, check voltage, just keep following the circuit to the lights or whatever, and see if the voltage has dropped before the load, where is should.

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This thread is kind of a mess…and I've left out loads of information.

Apologies…I feel like there's so many things I've done to remedy or troubleshoot - i've used pretty much every thread on here as well as other forums for reference for any other similar issues that are at all related.

 

I will add some more notable key points. 

 

All battery cables/grounds/terminals/fusible link as well as alternator wiring is NEW. Battery is used but tests good. All fuses have been replaced. 

 

I've chased voltage from battery and performed a few tests listed above with varying results…that is why in my opinion this issue is  very frustrating.

 

Some of my theories or possible issues…:

 

my original external voltage regulator (w/ both male& female plugs) were cut out of my wiring harness when I went to the GM alternator. Instead of cutting the plug off the volt. reg. and making the jumpers on the plug my only choice was to jump the wires directly into each other - these were soldered and heat wrapped and tucked back up into the harness.

 

-there should be no issues with this….right? same as if I jumped the wires after the plugs, obviously if they were still there.
 

My current wiring into GM alternator is just crimped with connectors into new GM plug on alt. Curious if the crimped connected are insufficient and causing issue...

 

 

 

 

The incredibly frustrating part about all of this is the inconsistency at which this issue arrises.

Here's an example:

 

Literally, I will start truck as  usual and pull light switch out to posing…then headlights…and all will be fine. I will even then be able turn on hazards…etc…no issue. 

At that point, when things appear to be working as they should , I will put the truck in gear and as soon as there's any load everything will die as noted above.

 

If any lights were on, they immediately turn off, engine dies as if shut off, and functions of the truck are "locked". 

No change to anything until I move the light knob back too off and the key back to the "off" position on ignition switch.

I'd say 50% of the time once the key is back in the off position things will "reset".

 

"Reset" meaning…charge light will illuminate and I can then start the car with no issue. 

 

The other 50% of the time I will be completely "locked out" with no function of anything until I disconnect the negative terminal and/or just wait it out. Typically a half an hour or so.

 

Some times I will get in the truck and start, and as soon as light switch is pulled even to "posing" the truck will die and everything with it.

Other times I will get in the truck and start, and posing/headlights will work - but turning on the hazards will kill the truck and everything again with it.

 

Other times I will turn the key to "start" and as soon as it makes the turn everything will blackout/lock me out until I "reset" - 

 

 

So repetitive in my explanations ...but I feel like the issue is possibly obvious to someone else!

 

Bahhh i'm going to be a bit frustrated if it's just something like a bad NEW fusible link...

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Something is loose. With the engine running...check the fusible link by moving it around. Pull on the wiring and move around the harness checking it. When the engine quits you've found the area to look closer.

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aaaaaaand I think I got it!

 

Thanks to datzenmike's recommendation I sourced a huge problem.

 

Truck fired up flawlessly with no signs of issue. All lights worked with no signs of issue other then quick flicker of charge light on dash when engaged.

With engine running I unhooked the main wiring harness looms near battery / old voltage regulator location and simply pulled on the harness.

 

First pull (maybe an inch away from wheel well) and truck begins to stall out and lights begin to flicker…until I quickly push harness back into original position.

 

I'm able to do this indefinitely and just pulling in different locations was able to isolate or that it appeared to be coming from the entry hole on firewall-into dash.

 

Crawl underneath and low and behold. sticking out like a sore fricking thumb. HOW did I miss this….???

I've been underneath the dash and overlooked it probably dozens of times.

 

Spade connector had completely popped out or was removed at some point…and just resting on each other. 

Lots of corrosion and obvious burn marks to connector sheath or cover.

 

Cleaned it all up and reconnected, wrapped it all up and so far so good!
 

Dash back together and taking for a shakedown. Will report back later

 

 

Thanks again x1000!
 

 

(keep it simple, stupid.)

 

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