Alternator Output Drops Above 45 C After 75 km

Started by Bret Cahill July 19, 2017
After 50 - 75 km driving the ignition system starts to fail.

Pull over and wait 2 minutes and then another 50 km is possible _without lights_.

It's hard to imagine anything cooling off in just 2 minutes.  There must be some
thresh hold where the rectifier or voltage regulator is really sensitive to even
small changes in temps.


Bret Cahill


Bret Cahill wrote on 7/19/2017 12:15 PM:
> After 50 - 75 km driving the ignition system starts to fail. > > Pull over and wait 2 minutes and then another 50 km is possible _without lights_. > > It's hard to imagine anything cooling off in just 2 minutes. There must be some
thresh hold where the rectifier or voltage regulator is really sensitive to even small changes in temps. Does this only happen during the day and not at night? What is the voltage on the system when you start running and when the engine fails, also with and without lights? I'm not sure how you can restart the engine if the voltage is so low the engine won't run. I'm thinking it is an issue with the engine control computer rather than the electrical system. You can get voltmeters off eBay that plug into your lighter socket. -- Rick C
> > After 50 - 75 km driving the ignition system starts to fail.
> > Pull over and wait 2 minutes and then another 50 km is possible _without
lights_.
> > It's hard to imagine anything cooling off in just 2 minutes. There must be some
thresh hold where the rectifier or voltage regulator is really sensitive to even small changes in temps.
> > Does this only happen during the day and not at night?
I avoid driving at night when it's really hot. LED headlights would solve the problem and are actually cheaper than voltage regulators if you can believe that.
> What is the voltage > on the system when you start running and when the engine fails,
I'll check it out.
> also with > and without lights? I'm not sure how you can restart the engine if the > voltage is so low the engine won't run.
The battery restarts the engine just fine. Autozone tested it claiming everything is A-OK with the charging system. Of course, the engine had been off for a couple of minutes so that test wasn't too useful.
> I'm thinking it is an issue with > the engine control computer rather than the electrical system.
I should have thought of that.
> You can get voltmeters off eBay that plug into your lighter socket.
I'll wire up a plug to a multi meter next trip into the heat. I should have thought of that too. Thanks again. You can conceptualize w/o language but you cannot think w/o language. Bret Cahill
Bret Cahill wrote on 7/19/2017 2:43 PM:
>>> After 50 - 75 km driving the ignition system starts to fail. > >>> Pull over and wait 2 minutes and then another 50 km is possible _without
lights_.
> >>> It's hard to imagine anything cooling off in just 2 minutes. There must be some
thresh hold where the rectifier or voltage regulator is really sensitive to even small changes in temps.
>> >> Does this only happen during the day and not at night? > > I avoid driving at night when it's really hot.
I'm trying to figure out if it *is* the heat. Heck, it could be something blocking the exhaust or something with the fuel supply.
> LED headlights would solve the problem and are actually cheaper than voltage
regulators if you can believe that. How do you know LED headlights will solve the problem if you don't know what the problem is?
>> What is the voltage >> on the system when you start running and when the engine fails, > > I'll check it out. > >> also with >> and without lights? I'm not sure how you can restart the engine if the >> voltage is so low the engine won't run. > > The battery restarts the engine just fine. Autozone tested it claiming everything
is A-OK with the charging system. Of course, the engine had been off for a couple of minutes so that test wasn't too useful. If your alternator stops working because of the heat, the battery will run down. The system voltage can't droop without the battery loosing charge. So if the engine starts ok something else is wrong. Do the headlights dim? That's an indication of low voltage to the headlights.
>> I'm thinking it is an issue with >> the engine control computer rather than the electrical system. > > I should have thought of that. > >> You can get voltmeters off eBay that plug into your lighter socket. > > I'll wire up a plug to a multi meter next trip into the heat. I should have
thought of that too. Thanks again.
> > You can conceptualize w/o language but you cannot think w/o language.
It can also be something as mundane as the ignition coil. Do you have one or several? If one it could be that. Or if you have an ignition resistor that can be opening in the heat. The symptom will be the engine starts while you turn the key to start, but as soon as you release it to ON, the engine dies. -- Rick C
> >>> After 50 - 75 km driving the ignition system starts to fail. > > > >>> Pull over and wait 2 minutes and then another 50 km is possible _with=
out lights_.
> > > >>> It's hard to imagine anything cooling off in just 2 minutes. There m=
ust be some thresh hold where the rectifier or voltage regulator is really = sensitive to even small changes in temps.
> >> > >> Does this only happen during the day and not at night? > > > > I avoid driving at night when it's really hot. >=20 > I'm trying to figure out if it *is* the heat. =20
This never happens below 40 C so heat is definitely one leg of the 2 legged= stool. =20
> Heck, it could be something=20 > blocking the exhaust or something with the fuel supply.
I always think it's a clogged fuel filter at first. Later down the road I = remember trying changing the filter so this issue is not a clogged fuel fil= ter. Maybe the fuel pump creates enough of a vacuum so that the pressure drops b= elow vapor pressure which should be quite high at 50 - 60C. Then the pump= could lose suction. The problem with that theory is the fuel system shoul= d not be affected by a load on the electrical system, especially a cam driv= en fuel pump.
> > LED headlights would solve the problem and are actually cheaper than vo=
ltage regulators if you can believe that.
>=20 > How do you know LED headlights will solve the problem if you don't know w=
hat=20
> the problem is?
Halogens draw a lot of power which hastens the onset / aggravates the mis f= iring enormously but _only when it is really hot_.
> >> What is the voltage > >> on the system when you start running and when the engine fails, > > > > I'll check it out. > > > >> also with > >> and without lights? I'm not sure how you can restart the engine if t=
he
> >> voltage is so low the engine won't run. > > > > The battery restarts the engine just fine. Autozone tested it claiming=
everything is A-OK with the charging system. Of course, the engine had be= en off for a couple of minutes so that test wasn't too useful.
>=20 > If your alternator stops working because of the heat, the battery will ru=
n=20
> down. The system voltage can't droop without the battery loosing charge.=
=20
> So if the engine starts ok something else is wrong.
The distributor ignition module is a suspect component. Maybe a combinatio= n of heat + a load on the electrical system for a slightly different voltag= e is too much for it. There isn't any easy way to dismiss that theory.
> Do the headlights dim? That's an indication of low voltage to the headli=
ghts. I don't remember ever having dim lights.
> >> I'm thinking it is an issue with > >> the engine control computer rather than the electrical system.
> > I should have thought of that.
> >> You can get voltmeters off eBay that plug into your lighter socket. > > > > I'll wire up a plug to a multi meter next trip into the heat. I should=
have thought of that too. Thanks again.
> > > > You can conceptualize w/o language but you cannot think w/o language. >=20 > It can also be something as mundane as the ignition coil. Do you have on=
e=20
> or several? =20
One. The resistances check out OK at lower temperatures. Maybe something = opens up in the heat.
> If one it could be that. Or if you have an ignition resistor=20 > that can be opening in the heat. The symptom will be the engine starts=
=20
> while you turn the key to start, but as soon as you release it to ON, the=
=20
> engine dies.
It'll start immediately and stay running until there's some combination of = too much electrical load + too much heat. Bret Cahill
Bret Cahill wrote on 7/19/2017 8:49 PM:
>>>>> After 50 - 75 km driving the ignition system starts to fail. >>> >>>>> Pull over and wait 2 minutes and then another 50 km is possible _without
lights_.
>>> >>>>> It's hard to imagine anything cooling off in just 2 minutes. There must be
some thresh hold where the rectifier or voltage regulator is really sensitive to even small changes in temps.
>>>> >>>> Does this only happen during the day and not at night? >>> >>> I avoid driving at night when it's really hot. >> >> I'm trying to figure out if it *is* the heat. > > This never happens below 40 C so heat is definitely one leg of the 2 legged
stool.
> >> Heck, it could be something >> blocking the exhaust or something with the fuel supply. > > I always think it's a clogged fuel filter at first. Later down the road I
remember trying changing the filter so this issue is not a clogged fuel filter.
> > Maybe the fuel pump creates enough of a vacuum so that the pressure drops below
vapor pressure which should be quite high at 50 - 60C. Then the pump could lose suction. The problem with that theory is the fuel system should not be affected by a load on the electrical system, especially a cam driven fuel pump.
> >>> LED headlights would solve the problem and are actually cheaper than voltage
regulators if you can believe that.
>> >> How do you know LED headlights will solve the problem if you don't know what >> the problem is? > > Halogens draw a lot of power which hastens the onset / aggravates the mis firing
enormously but _only when it is really hot_.
> >>>> What is the voltage >>>> on the system when you start running and when the engine fails, >>> >>> I'll check it out. >>> >>>> also with >>>> and without lights? I'm not sure how you can restart the engine if the >>>> voltage is so low the engine won't run. >>> >>> The battery restarts the engine just fine. Autozone tested it claiming
everything is A-OK with the charging system. Of course, the engine had been off for a couple of minutes so that test wasn't too useful.
>> >> If your alternator stops working because of the heat, the battery will run >> down. The system voltage can't droop without the battery loosing charge. >> So if the engine starts ok something else is wrong. > > The distributor ignition module is a suspect component. Maybe a combination of
heat + a load on the electrical system for a slightly different voltage is too much for it.
> > There isn't any easy way to dismiss that theory.
Sure there are lots of ways. Try taking some measurements.
>> Do the headlights dim? That's an indication of low voltage to the headlights. > > I don't remember ever having dim lights.
Then there is nothing wrong with the voltage. Forget the alternator, regulator and system voltage.
>>>> I'm thinking it is an issue with >>>> the engine control computer rather than the electrical system. > >>> I should have thought of that. > >>>> You can get voltmeters off eBay that plug into your lighter socket. >>> >>> I'll wire up a plug to a multi meter next trip into the heat. I should have
thought of that too. Thanks again.
>>> >>> You can conceptualize w/o language but you cannot think w/o language. >> >> It can also be something as mundane as the ignition coil. Do you have one >> or several? > > One. The resistances check out OK at lower temperatures. Maybe something opens
up in the heat. Duh, that's the point. It can be opening up at high temps. Same with the resistor.
>> If one it could be that. Or if you have an ignition resistor >> that can be opening in the heat. The symptom will be the engine starts >> while you turn the key to start, but as soon as you release it to ON, the >> engine dies. > > It'll start immediately and stay running until there's some combination of too
much electrical load + too much heat. I'm talking about after it fails and won't run. Above you said you have to wait 2 minutes until it will start. You need to check things *then*. No point in checking them when they are working. Does the engine stumble, lose power and die or just quit like you turned it off? -- Rick C
On Wed, 19 Jul 2017 09:15:14 -0700 (PDT), Bret Cahill
<bretcahill@aol.com> wrote:

>After 50 - 75 km driving the ignition system starts to fail. > >Pull over and wait 2 minutes and then another 50 km is possible _without lights_. > >It's hard to imagine anything cooling off in just 2 minutes. There must be some
thresh hold where the rectifier or voltage regulator is really sensitive to even small changes in temps.
> > >Bret Cahill >
99% of the time alternator problems are caused by brushes. First suspect with any vehicle that has 50K+ miles on it. (although some new alternators don't have brushes... and some go for 200K before they wear enough) Warm temps can cause the metal in the holders or the insulating material to expand causing the brushes to bind in the slip ways. If the brushes are at the end of their life, the small amount of run-out (wobble) can kick the brushes up into the slip holders where they stay until it cools enough so the spring can push it back into contact with the rings. How many miles on the car? Brushes are cheap - ~$4 ($8 in NY to fix my OM's car) take it to a garage and they replace the alternator for $300, or claim they rewound the rotor for about that same amount. Pressed in diodes on the alternator housing can also cause that, if they are rusted between the diode case (steel) and aluminum alternator.
How about replacing it with a 140A alternator...

<https://www.amazon.com/ALTERNATOR-PETERBILT-19011187-19011258-321-758/dp/B008BB4OOS>:-}
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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default wrote on 7/20/2017 6:18 AM:
> On Wed, 19 Jul 2017 09:15:14 -0700 (PDT), Bret Cahill > <bretcahill@aol.com> wrote: > >> After 50 - 75 km driving the ignition system starts to fail. >> >> Pull over and wait 2 minutes and then another 50 km is possible _without
lights_.
>> >> It's hard to imagine anything cooling off in just 2 minutes. There must be some
thresh hold where the rectifier or voltage regulator is really sensitive to even small changes in temps.
>> >> >> Bret Cahill >> > 99% of the time alternator problems are caused by brushes. First > suspect with any vehicle that has 50K+ miles on it. (although some new > alternators don't have brushes... and some go for 200K before they > wear enough) > > Warm temps can cause the metal in the holders or the insulating > material to expand causing the brushes to bind in the slip ways. If > the brushes are at the end of their life, the small amount of run-out > (wobble) can kick the brushes up into the slip holders where they stay > until it cools enough so the spring can push it back into contact with > the rings. > > How many miles on the car? > > Brushes are cheap - ~$4 ($8 in NY to fix my OM's car) take it to a > garage and they replace the alternator for $300, or claim they rewound > the rotor for about that same amount. > > Pressed in diodes on the alternator housing can also cause that, if > they are rusted between the diode case (steel) and aluminum > alternator.
There is nothing wrong with his alternator. He has not measured anything to show there *is* a problem. His engine stops running when it is hot out and he jumped to a conclusion that it had to be an alternator problem. At this point he has reported no measurements that would support the idea that the problem is the charging system. He has said the light do not dim and the engine starts fine after things sit for a couple of minutes, so I don't see how it can be the charging system. -- Rick C
On Wednesday, July 19, 2017 at 12:15:18 PM UTC-4, Bret Cahill wrote:
> After 50 - 75 km driving the ignition system starts to fail. > > Pull over and wait 2 minutes and then another 50 km is possible _without lights_. > > It's hard to imagine anything cooling off in just 2 minutes. There must be some
thresh hold where the rectifier or voltage regulator is really sensitive to even small changes in temps.
> > > Bret Cahill
I had the same problem. I would squirt some Cold Spray onto the fuel pump and away we go... Vapor lock? Bad vent on gas cap?