tooltime

Hey guys, I was trying to figure this out on my own, but have failed! My car will not come off the choke. Idle is about 1500 and the choke light stays on all the time. It buzzes after a bit, like it's trying to turn off, but still stays on. I had someone tell me it's my alt, it's not. I'm getting 14v out of it. I have replaced the electric thermo on the carb and the clip that connects to it. I also checked the voltage to the clip to ground. I get 12 to 14v there as well, I made sure it's engaged into the tang correctly and have it set to where the notch in the thermo is aligned to the larger center marker. There is a tab just behind the thermo housing that comes up as the car is started, you can press that down which releases the choke and the car runs fine. As soon as you hit the gas the choke is re-engaged. So where else do I look? Thanks again for the help. Matt

sofakingdom

iTrader: (1)

The alt is bad.

Blee dat.

The alt is actually a 3-phase generator. The problem yours has is that 2 phases are working, but one is not.

The specific part that has failed is most likely the diode trio.

Replace it.

The choke problem most likely is localized to the choke; probably either the heater is burned out, or the carb body isn't well grounded.

But, replace the alt first, and go from there.

tooltime

Is there a way to test the alt to see if that is it or not? You talked about the heater being burnt out. Are you talking about the choke thermo, electric coil? I'll replace the car at the rate that I'm going. Id like to make sure that what I replace is truly to blame. Thanks for your help. Matt

five7kid

iTrader: (14)

Take the alternator to most any parts store chain (NAPA, O'Reilly, Advance Auto, etc.). They should have a machine that can test it, including the diodes.

tooltime

Isn't voltage, voltage. If I have 14 volts going to the new thermo choke all that it needs. Power heats up the coil opening the choke? Why does the choke close each time I hit the gas? Is that spring in the stat too strong? Is there something else causing the choke to close or it that the only thing that operates the choke. I've been looking online and in my manuals but it's pretty vauge as far as what operates the choke. Thanks for the help.

sofakingdom

iTrader: (1)

NO.

Stop arguing, and replace the alt.

Just because it's "vague" TO YOU, doesn't mean it's "vague" TO EVERYBODY. But at the same time, just because it's NOT "vague" in the least to me (I'm underemployed as an electrical/electronic engineer ATM) doesn't mean I can explain it to you in terms you'll understand.

Your alt is bad. Period, paragraph, end.

Replace the alt.

Joe Tag

iTrader: (4)

Sofa, you really seem to have a way of sounding like a sarcastic @$$ in most of your posts. Just because you think you know it all, it doesn't mean you should belittle everyone that comes in here asking for help. You really should have a little more tolerance if you are really here to help and not just try and make people feel like they're "so f****ing dumb" for using this site for what it is intended for. Seriously, take a break if it's getting to you.

eseibel67

Participants on this site are lucky to have a crusty guy like Sofa. His advice is rock solid, with a heaping helping of comedy on top. WAY MUCH preferred over a "nice guy" that can't help you.

excessiveego

you may not know as much as you think. Now, i have some knowledge of electronics but this information was confirmed by my father who is currently making in excess of $80 an hour working for a telecommunications company for the past 35 years working on 3 phase AC generators and electronics worth millions of dollars with rectifiers that provide DC power to the systems that provide phone, internet and TV service to whole cities.

you are talking about DC which is nothing like AC. The alternator produces 3 phase AC which is then passed through a rectifier converting it to DC. If only 2 phases are being passed through the rectifier you will still get 13+ volts but your amperage will be lower.

if you have a good battery your amperage will be high enough to shut off the choke assuming you are reading 13 volts. If your battery is not good you would get a large drop in voltage when you turn the key to run without the engine running, if in doubt hook up a battery charger.

the only way to truly determine if your alternator is bad as sofa describes would be to check the amperage at your battery. But even if your alternator is only putting out 2 phase it shouldn't cause your problems as you describe them.

Now, to Sofa, if he provided information elsewhere that helped lead you to this conclusion I apologize, but based on what he said here you just cant come to that conclusion.

FoxGTA87

I've been working on cars for over 30 years. I have never seen a alternator cause a choke to stay on! Good grief. Got to love trolls.

tooltime

I just wanted to have it explained to me. I'm trying to learn how this works. Seems to me that the choke needs to be set. I just wanted a way to trouble shoot it before I go replacing a $300 dollar muffler bearing, if you know what I mean. Didn't mean to challange anybody here.

sofakingdom

iTrader: (1)

The way the circuit works is, the voltage produced at the junction of the cathodes of the diode trio, which is the same voltage that turns off the light, also releases a relay in the "convenience center" whose coil is in parallel with the light, which then applies voltage to the choke. The purpose of this is so that the choke does not get heated if the key is merely on and the engine is not running.

Since the alt is 3-phase, if one phase is out, then 2/3 of the time there will be voltage generated, but the other 1/3, there will not. Under this circumstance the relay coil will have switched battery on one end and alt output on the other 2/3 of the time, i.e. essentially zero voltage across it, but will have battery on one end and ground on the other 1/3 of the time, which is enough to keep it operated. Since it completes the circuit that sends power to the choke when it releases, this creates the situation at hand.

Furthermore, at low RPMs, the 2/3 - 1/3 duty cycle at this point allows the relay to release partway during the 2/3 part, but then re-operates during the 1/3; which is what makes the buzzing sound.



Now you know.

Replace the alt.

Whether some troll who has been changing oil and mounting tires for 30 years has ever seen it or not.

Replace the alt. It's the cause of the problem.

tooltime

Hey Sofakingdom, thanks for the help on this one. I replaced the alt and reset the choke. Never in a million years would I have figured that one out. I do appreciate the explination, I like to learn as much as I can about my car as I can, that's all I was after not trying to doubt your knowledge. Anyway, to all the trolls out there, it did work and he was correct!!!! I'll pass it along, the dumb' down version but I'll still pass it along if I get the chance. Thanks again guys.

Joe Tag

iTrader: (4)

I never doubted the validity of his advice. Just the method of delivery.

MD83Z

This is my favorite thread ....i will try to copy the diagram so it won't fade away into 20013