521 electrical issue

[ttyR2]

I discovered that the positive battery cable was bad on the 521. I can't say I've ever seen this happen before. Even after cleaning, the electrical system was dead. A battery charger clipped onto the battery cables showed no battery attached. Take the positive cable off and hook the charger directly to the battery, works fine. Odd.

 

After replacing the battery cable everything works fine, but I picked up an issue. With the key off and removed, when I connect the positive cable, the relay in the picture below triggers and the IGN light is on in the dashboard.

 

 

I unplugged the cable from the back of the ignition switch to see if the switch was bad and that didn't make a difference. Any ideas on what might be shorting out causing that relay to stay on when power is applied? With the IGN light staying on, I'm not going to leave the battery connected for now because I'm worried about burning up the points or killing the battery.

Edited October 2, 2022 by ttyR2

[banzai510(hainz)]

was a electric coke carb on the truck then tyou put a later model alternator?

I still see the old volt reg so I will assume NOT. All your saying is you just replaved the +pos battery cable that it????????????

 

I have Battery cable go bad by them cracking when I overtighten them then they split maiking a loose connection.

 

 

I think that is the choke relay. Try disconnecting it.  I always went with a Manual weber carb. or disconnected the elelctric choke on the carb if you have that and see where you go and report back.

 

 

was some else done? swapped

 

always ck your fuses also. %21s have water corrossion issues and I always go there 1st

Edited October 2, 2022 by banzai510(hainz)

[ttyR2]

Unbeknownst to me, it's been doing this for a while. I'm still teaching the kids about reporting stuff instead of just continuing to drive 🙂

 

All I did today was replace the battery cable and the brake master cylinder...honest. I'll double check the fuses. I do need to find out why the IGN light is on.

[datzenmike]

The '72 was the first year for the electric choke. The 620 has a choke heater relay but I don't know about the 521. There was a heater relay and a relay for the second set of points.

 

If all that was changed was the positive battery cable then this problem has been there for a long time. Did the battery ever go dead over a long weekend where the truck was not started?

 

What are the color wires going to the plastic plug of that relay.

[ttyR2]

I'll have to look.

 

If I unplug one relay at a time and connect the battery, that relay and the alternator regulator both trip. I overlooked noise from the alt regulator. The kiddo hasn't had to jump the battery at all as far as I know, but out of this troubleshooting, I did discover the battery is bad. It must have been a spontaneous failure as he drove it to school on Friday. When I do a basic load test, it only shows 10 volts or so, and goes to zero as soon as a load is applied. I had another spare used battery that passed a load test and put it in. Everything in the truck acts the same though...but now it starts and runs which it didn't do with the old battery.

[datzenmike]

Humor me. Unplug the voltage regulator.

[ttyR2]

Further info. I disconnected the lead that goes from the battery to the fuse box and that didn't make any difference. The relay and regulator still "trip" when the battery is connected.

 

I also unplugged the regulator completely, the other relay still tripped and the IGN light was still on.

Edited October 3, 2022 by ttyR2

[mainer311]

Hainz is right, it’s the electric choke relay:

[datzenmike]

4 minutes ago, ttyR2 said:

Further info. I disconnected the lead that goes from the battery to the fuse box and that didn't make any difference. The relay and regulator still "trip" when the battery is connected.

 

Pull the plastic plug from the back of the alternator. Don't forget to unplug the volt regulator too. has to be one of those.

[mainer311]

If there’s a short in the VR, it’ll send voltage down the stator wire “N” and energize the coil in the choke relay. Do what Mike said and unplug the VR to see what happens.

[ttyR2]

Ok. I unplugged the alternator regulator previously and that made no difference. I plugged it back in and then unplugged the two wires from the back of the alternator and now everything stays quiet. If only unplugging the connector at the alternator stops the issue, what's that pointing to? Bad diodes in the alternator? Wiring?

Edited October 3, 2022 by ttyR2

[mainer311]

Sounds like a short in the alternator. Somehow voltage is getting from the battery post to the N (yellow wire) connection at the back of the alternator, even with the engine off. I would take a multimeter and see if there’s voltage at that connection.

[banzai510(hainz)]

the light will come on when it senses a ground or a 12volt difference to make the light come on. When the alt works both sides will have 12volts thus reading o volts across the light so it will not come ON.  Like a bird on a wire.

 

i WOULD PULL THE CHOKE RELAY CONNECTOR OR WIRE FROM CHOKE

This is only a best guess. I would swap a alternator in there. but I have spares so its ez for me to trouble shoot.

 

ck the T connector

 

 

as for kids driving this? I wouldnt !!!!

Guy at work his son whos going in college said the oil light was on  for a few days before the motor went bad. He thought it was time to changed the oil. WTF!!!!!!

 

 

Buy a version of thus and trust it. You will catch this before it goes bad, Harbor freight has a version for like 6$

 but they work. If you over volt or undervolt during a load youll see it

https://www.summitracing.com/parts/ino-3721?seid=srese2&utm_source=bing&utm_medium=cpc&utm_campaign=Brands+|+I&utm_term=4581871113123102&utm_content=GSAPI1

 

be honest I would never get more than a year out of a Vatozone or O riley alternator before it went bad.

go with the japan made volt regs also. otherwise there is not much to the 521 electrical system

 

Edited October 3, 2022 by banzai510(hainz)

[datzenmike]

15 hours ago, mainer311 said:

Sounds like a short in the alternator. Somehow voltage is getting from the battery post to the N (yellow wire) connection at the back of the alternator, even with the engine off. I would take a multimeter and see if there’s voltage at that connection.

 

Bad diode? Ask son if he had to get a boost to get going. Maybe connected jumper cables backwards

[ttyR2]

I bought a reman alternator from O'Reilly's. Lifetime warranty but that's no good when it leaves you stranded. Once it's installed, I'm going to pull the original one apart and check all the components.

[Crashtd420]

If you haven't installed the alternator yet you might think about swapping it a newer internally regulated altenator instead....

Then eliminate the external regulator.... the picture mainer311 posted is the way to write it

... the only thing not correct in that picture is the choke relay.... if you need the choke relay you can cut the yellow at the relay and attach to the white and blue ignition wire. Then the relay only activates when the ignition comes on..  otherwise the relay will stay on...

[datzenmike]

It's a tight fit so get the '78-'79 620 alternator that fits the truck and is internally regulated.

[banzai510(hainz)]

3 hours ago, ttyR2 said:

I bought a reman alternator from O'Reilly's.

so is it fixed right now?

[ttyR2]

Haven't had time. Hopefully tomorrow.

[ttyR2]

Installed the alternator and all is well in the world again. I did find the (what I think is) supplementary ground wire was not connected previously to the old alternator (the small black wire).

[mainer311]

It's a good idea to have a massive ground from the alternator case to either the frame or engine block, or both. 

[ttyR2]

It's pretty small but I made sure it got cleaned and reconnected.