Double whammy

[1969CoronetR/T]

My alternator went 'bad' on my Demon last week and it was stuck in the garage for a few days. So I went to take my Coronet out for a ride and it would not start (I usually drive it once a week or less) and I used my portable jumper to start it. The battery test above 12 volts and it was still hard to start. I drove to a friends house about a hour away and stopped the engine to fill it up with gas and it needed jumped again as it would not turn over. After half of dozen tries, it finally started and then died again in front of the house. A mechanic (engine rebuilder) told my he thinks it is the starter and not the alternator as it will only start with a jump. How can you test the atlernator to rule this part out? How can you test the starter to rule it out?
Thanks,
Mark

 

[70WM21 W1 V6B]

An easy way to check the alternator(1/2" & 9/16") is to take it off and drop by your local parts store and have them test it, same with the starter, sometimes starters will go bad and short out inside and draw the battery down. I am assuming your talking about a 69 Coronet if so check the voltage regulator on the firewall also. Make sure the engine is grounded from the firewall to the rear of the block.

 

[morbidgoat]

if your battery is reading 12 volts when not running and cant start your car but a booster pack can you have a bad/weak battery. as for the alt what volt do you get at the battery when the car is running?

 

[1969CoronetR/T]

12 + running or not running at the battery. I have a new battery that I bought as I thought it was a simple dead battery, but my portable jumper read 12 volts so now I am confused.

 

[YY1]

I think when running, more than 12 should be the reading, something like 13-15.

A simple trick to check the alternator is to pull a battery cable while the car is running. It should stay running. If it dies, the alternator is not putting out enough.

My 70 Bee used to burn out one diode in the alternator frequently.

I got to the point of carrying a box full of alternator parts including several rear shells with newly replaced diode trios in them.

I could often be spotted off the side of the road rebuilding the alternator.

Got it down to about 15-20 minutes, and could tell by the guage needle position when one let go...before it lost enough juice from the battery to start.

If that happened while I was out, the first thing I'd do the next day was ohm out the diodes from the shell I took off, find the bad one, and solder in another one from a junk yard alternator.

That way I got 5-6 rebuilds from one $15 part, rather than buying a new $40 alt every couple of weeks.

Never did find out why it did this. Went through several reulators in several styles, next stop was an adjustable one.

I also had a bad guage in a 67 Coronet. It worked, and showed "charge", but sapped the system, and drained the battery.

That is the only electrical problem I ever paid someone else to fix.

 

[1969CoronetR/T]

I will pull the negative terminal once it is running to check the alternator and maybe replace the starter. It would die sometimes if I hit a large bump (as if the battery cable was loose), but it would fire right back up without and hesitation. It seems to be getting worse as it will not even turn over or make a single sound when the key is turned,
Thanks,
Mark

 

[74sundance]

A bad starter can and will draw more then the 12 volts your battery has, thats why the boost pack helps it start.Get it running and put a volt meter on the batt it should read between 12-15 volt while running...If not put the volt meters (-) test lead on the (-) batt post and put the (+) test lead on the nut for the big red power wire on the back of the alt.You should see 15volts there.If you have 15 volts on the alt red wire check your Voltage regulator.Other common causes are bad connections to grounds as well as to the starter, corrosion will wick up the starter cable reducing the amount of power allowed to the starter,this can happen at the Battery cables as well.I would think the starter or the connection to it is the problem.Next time it wont start have a friend tap the starter with a hammer while your laying on the key trying to start it,if it fires get a new starter

 

[74sundance]

had an after thought You can test your ignition switch by putting the volt meters (+) test lead on the smaller stud on the starter solenoid and the (-) lead to a good ground.Have a bud hit the key,you should see 12volts when the key is in the full forward position (start position) Or try and jump the two studs on the back of the solenoid it's on the side of the starter.Use a screw driver to bridge the gap between the two..If the starters good it will crank.Make sure the car is in park and that the parking break is on for this test

 

[74sundance]

After telling you how and what to check for I ended up doing it on my 74 Charger lol..I went out to the shop and hit the key after installing a rebuilt column and the sucker wouldn't do any thing....It was a combo of problems though.
1) loose power wire to the starter.
2) bad wires/connections at the battery.
3)The top nut on the starter relay was loose.
after I fixed all the little things it fired rite up

 

[1969CoronetR/T]

Thanks. I was told that if you ran a wire to the coil from the starter and hit it with a coin or screwdriver it would start up. I quess it was an easy way to hot wire a car in the old days per the engine builder.

 

[YY1]

Hmm, this thread is starting to sound JUST like my 70 Bee!

At one point, it also lost the ability to start from the key.

I spent several weeks with an aligator test lead from one of the working hot wires under the hood to the dist side of the coil. To start, I jumped the solenoid with a screwdriver, and to stop, I unclipped the test lead.

Made for an interesting show and conversation starter.

That car got nicknamed the Millenium Falcon due to the fact that it could make the kessel run in under a given number of parsecs, but always seemed to have minor system failures that could usually be rigged with a temporary work-around, while uttering the phrase "come on baby...hold together".

Finally discovered the main hot through the bulkhead connector was corroded inside the insulation. Note the temporary fix in this pic, after I found the problem.