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Low voltage - what else can I check?

SnowDrift

SnowDrift

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1994 K1500 Suburban

We just replaced the battery and alternator because the voltage kept dropping off when the electrical system was under a load, especially with the a/c on. It was to the point that the a/c on and blowers on high upon startup one day, the engine died twice right when I started it up.

What else can I check that could be causing the voltage to read low and not seem to recover a full charge? The turn signal causes the needle on the gauge to flicker much more than I think is normal, also.
 
NVW said:
Bad cables or grounds
Click to expand...

Both.

if you can see into the end of the cable ( at either end ) and you find green ( like the Statue of Liberty Green ) then its waaaayy past time for new cables..
 
Thanks guys. I guess that's what I'll be looking at. With 204,000 miles on the clock, it's surely due for a set. I didn't think grounds would cause those symptoms, but I'll dig into them, for sure.
 
Bad grounds are the cause of 95% of all electrical issues. I agree with the others, check cables and grounds first, and probably just replace the battery cables. The new cables will have less resistance than old ones, and you'll probably notice things like brighter headlights and easier cranking, to name a few.

Grounds never cause "normal" problems, the problems they cause are wacky and weird.
 
Get a volt meter. Put is from the charge wire on the alt to the positive battery and record the small voltage reading. Do the same for charge wire on alt to the main power bus. 1994 I think over over the coolant tank passenger side. Then do Power bus to positive battery.

You are checking for voltage drop on the battery to main bus connection and alternator to main bus connection. Also alternator to battery.

Any large voltage drop indicates a corroded wire or connection. You may have to replace the battery cable that goes to the main bus.

Also pull and check fuses for corrosion and good connections. Fusible links from the main bus can get weak with age and start to fail.

A big three ground stereo install type kit that puts the alternator wire to the battery helps bypass these old corroded wires.
 
I did find some corrosion on the ground cable at the frame on the passenger side under the coolant overflow. I cleaned it off and reinstalled and put Fluid Film on it to reduce future corrosion. It didn't solve the problem, though and I'm not sure it made a difference at all.

Any idea on where I can get a fusible link wire that comes off the battery to the alternator? I fried that a while back and have it rigged together. I'm thinking I should check that first. I believe I asked the dealer about it when I did it and I had to buy the whole cable, not just the section I burned.
 
I would add some grounds as the ground cables can go bad. Frame to engine and fender to engine. Battery eyelet end cables, around $10.00 each at the parts store will do. These are the cables without the side post or top post connectors but ring terminals on each end.

fusible link wire:
http://www.madelectrical.com/catalog/fusible-link.shtml
 
low voltage 94 suburban 1500

Bingo, bingo, bingo, exactly my symptoms. Constant low voltage especially when AC is on and turn signals or lights. A new battery has made no difference that I can tell. Recently had several times when truck would not start or even turn over. That has not recurred since the new battery. Can someone give me a heads up on grounds for a 94 Suburban. I don't know anything about grounds or their locations. I have already ordered new battery cables. Thanks, W. Lee
 
I have the same prob on my 1990 suburban, but when I turn on a/c It will die. As in nothing ( no engine light no cranking etc) but if I wait and shake the wires on the back of alt it will come back to life. I am going to change all cables and grounds and pray that this works.
 
SMOKEYRCN3 said:
I have the same prob on my 1990 suburban, but when I turn on a/c It will die. As in nothing ( no engine light no cranking etc) but if I wait and shake the wires on the back of alt it will come back to life. I am going to change all cables and grounds and pray that this works.
Click to expand...

Sounds like you have faulty wires as seen by the wiggle test.
The older trucks, and specific to 1993, run the main bus wire between the engine and exhaust manifold before going to the battery from the bus bar on the firewall. Locate this wire and cut it out of the system as the insulation may have burned off. The battery tray is another rub through location for this wire and the main battery positive cable. Replace this wire using the fusible link from the old one with a new wire routed around the air filter.

Check the alternator wire for shorts as well.

Check all grounds bay taking them apart and cleaning them up. Add a new ground wire from the frame to the engine just in case the one on the passenger back of the engine has fallen apart from age.
 
Hi oldsman, welcome to the forum.

What is your vehicle, please desribe your details, and what you have done so far? What is battery voltage doing? Have you disconnected the battery(s) and done a load test?

Without knowng anything i can tell you disconect and clean both ends of negative and positive battery cables. If your engine does not get its ground directly from the negative cable, remove and clean the jumper ground to it. Thats all free and cant hurt anything.
 
I have had alternator checked. Battery post are clean. Voltage did run about 14 now about 9 volts. When moving voltage drops causes gages dropped oil pressure gage dropped so low that check gages light come on.engine starts to stall.out
 
Load test batteries individually with them disconnected from the truck.

You said posts are clean, did you clean other end of cables connection point? What is battery cable condition?

Test for current draw with key on, engine off. Then do the same with engine running. Both voltage and amperage.
 
Cable ends are good /clean. The postive side is little rusty but has been that way for some years. I failed to mention that I had a wire that goes to junction block burn into because of wire going from junction block to starter
 
70 Oldsman said:
Cable ends are good /clean. The postive side is little rusty but has been that way for some years. I failed to mention that I had a wire that goes to junction block burn into because of wire going from junction block to starter
Click to expand...
Shorted out. I repaired that. Voltage is low even truck not running.
 
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