Dmch alternator issue

[Dontilgon]

Just installed there alternator,when all
Was said and done I now have this problem. I cant think of anything I did wrong that would case this issue https://youtu.be/_OWN-zleySwm.

[dmcnc]

Appears to be more likely an idle issue...was the idle like that prior to your alternator swap?

[Jonathan]

Belt slipping? Not tight enough?

[Dontilgon]

Appears to be more likely an idle issue...was the idle like that prior to your alternator swap?

I did not have this issue prior to the swap. The previous alternator was oem and still working.i believe the belts are tighten properly being I put the stainless alternator adjuster on. If anything I was concerned I may of over tighten.Alternator appeared to be straight forward install: cleaned mounting bracket , 3 red bunch wires to alternator and single alternator wire to single wire from factory harness.Also needless to say when the fans kick on it gets worse.
List of things I did at the same time

Dmch starter
Dmch alternator
New interstate battery mtp-78
Pressure regulator
Oil change
Remove catalytic convertor and replace with test pipe

[dmcnc]

You could do a voltage drop test between the alternator and the battery on both the ground and + sides of that circuit and/or reinstall the old alternator (is it a Motorola?) to see if the issue continues.

[Michael]

A slipping belt would be worse as the rpms rose. It looks like a dead battery to me but you said it was new.

Get your mulitmeter and watch the voltage. Check it at the battery and at the alternator. If the battery is showing less than 12.8v while running, charge it and try again. It is possible you just got a bad alternator with a bad diode.

[Dontilgon]

Okay I will check voltage and report back. Sad was looking forward to taking it out tonight thinking with all the “upgrades” I would feel more confident driving it. Anyways prior to these installs, it would sometime chase idle for a couple of second on start up when smooth out perfectly. When first started after install it immediately sounded totally different. Okay out to the garage .....

[Bitsyncmaster]

I did not have this issue prior to the swap. The previous alternator was oem and still working.i believe the belts are tighten properly being I put the stainless alternator adjuster on. If anything I was concerned I may of over tighten.Alternator appeared to be straight forward install: cleaned mounting bracket , 3 red bunch wires to alternator and single alternator wire to single wire from factory harness.Also needless to say when the fans kick on it gets worse.
List of things I did at the same time

Dmch starter
Dmch alternator
New interstate battery mtp-78
Pressure regulator
Oil change
Remove catalytic convertor and replace with test pipe

I bet the test pipe has caused the idle hunt. You need to adjust your mixture now.

The idle hunt is probably causing a low voltage condition when the idle drops below 700 RPM.

[Dontilgon]

14.9 at the battery but It obviously fluctuates with the idle.Interesting thing I started it this morning and it idled perfectly for a good minute or two,opened up the engine bay and noticed the cold start unplugged. Plugged back in and it stayed the same. I noticed has the car started heating up it seemed to have gotten worse and then it was back to its old tricks

[David T]

Some hunting is normal. To reduce it you must make each cylinder as balanced (equal) to each other as possible. You also have to find and fix all vacuum leaks. Your car sounds pretty normal.

[Jonathan]

You changed out a lot of different things at the same time. I bet the idle hunt and the voltage gauge going up and down are two separate issues.

Between changing out the pressure regulator and removing the catalytic converter, you probably now need to reset the CO mixture. Enough pressures or back pressures may have changed that the system doesn't know where it is anymore. I would go through that procedure in the manual to test and see that your idle system is all working as intended, O2 sensor is fine and all the rest of that and THEN see about adjusting the mixture.

Does your battery light come on when you first turn the key to accessories? Have you tried contacting Houston to ask specifically about how that alternator was supposed to be installed in case you missed something?

[Michael]

A slipping belt would be worse as the rpms rose. It looks like a dead battery to me but you said it was new.

Get your mulitmeter and watch the voltage. Check it at the battery and at the alternator. If the battery is showing less than 12.8v while running, charge it and try again. It is possible you just got a bad alternator with a bad diode.

My mistake. I thought you were illustrating the voltage gauge and panel lights dimming at low rpm. The idle surge would most likely have nothing to do with an alternator issue.

[Dontilgon]

You changed out a lot of different things at the same time. I bet the idle hunt and the voltage gauge going up and down are two separate issues.

Between changing out the pressure regulator and removing the catalytic converter, you probably now need to reset the CO mixture. Enough pressures or back pressures may have changed that the system doesn't know where it is anymore. I would go through that procedure in the manual to test and see that your idle system is all working as intended, O2 sensor is fine and all the rest of that and THEN see about adjusting the mixture.

Does your battery light come on when you first turn the key to accessories? Have you tried contacting Houston to ask specifically about how that alternator was supposed to be installed in case you missed something?

I have a new 02 sensor, I will change and then start up cold. I will record the cold start up. After that I will go in the manual to look at the procedure. Also I’m sorry it was the pressure sending unit I changed not the regulator. I’ll be back....

[Michael]

I have a new 02 sensor, I will change and then start up cold. I will record the cold start up. After that I will go in the manual to look at the procedure. Also I’m sorry it was the pressure sending unit I changed not the regulator. I’ll be back....

When I was dealing with a hunt (mine was across the rpm board), O2 sensor fixed the issue.

The O2 sensor does not affect the car in open loop so don't expect a new o2 sensor to affect cold start up.

[Ron]

$.02

Open or closed loop, the 02 sensor has little to do with starting. Once started, a shorted or open 02 sensor would lie to the system whether the engine is hot or cold.
I'd do the tests at D:04:15 before changing yet another thing.


14.9 at the battery but It obviously fluctuates with the idle.Interesting thing I started it this morning and it idled perfectly for a good minute or two,opened up the engine bay and noticed the cold start unplugged. Plugged back in and it stayed the same. I noticed has the car started heating up it seemed to have gotten worse and then it was back to its old tricks
14.9V fluctuating is too high.

Depending on how long it ran, it could be that it ran ~OK in closed loop then started acting up when it went into closed loop because you changed the pipe, as others have mentioned...
Warm it up and check (only, for now) the CO dwell.

[David T]

14.9 volts doesn't bother me too much unless the battery is fully charged. Once the battery is fully charged the voltage should drop down to around 13 volts. At idle the alternator can't put out it's full rated output so that is no way to test it. As long as the electrical system is over 12 volts this has no effect on your idle. Your hunting (fluctuating) idle is due to cylinder imbalance and the test pipe could have magnified it. You have 2 distinct things here. The charging system and the idle. While they have many things in common it is 2 separate problems. A new O2 sensor may not make any difference, the frequency valve is fluctuating as it should resulting in your hunting. Typically a bad O2 sensor would make the idle NOT hunt since it isn't responding to the changing oxygen content in the exhaust. Charge up the battery and check the voltage after a few minutes of running and see if it settles down to around 13 volts. Can't give you an exact number since it is affected by the ambient temperature. I would keep the cat, removing it won't give you much more power but it will make the exhaust louder. To get a little more power you have to remove the cat and change to headers. I wold not mess with the mixture adjustment to correct a hunting issue. To fix the hunting I would do a full tune-up and find and fix any vacuum leaks. Then check the A/F ratio, aka dwell, aka duty cycle.

[Ron]

David, if it is fluctuating @ 14.9V while idling, then it hits 15V (or more) which it should never do. And as you say, it doesn't put out fully at an idle... I agree that checking the voltage at an idle is not a proper test, but below ~13.5 V and above ~14.7 are signs of bad alternator. In this case, it should should be given several minutes to replenish the battery (from starting) and then allowed to run several more minutes to see just how high the voltage goes with everything turned off (then on, for other reasons). Or just pull it and have it properly tested.

[Bitsyncmaster]

If the battery has developed an open cell than voltage can go above 15 volts with the alternator working. If the alternator tests good get the battery tested.

A good battery the voltage will increase as it charges due to limiting current of the battery charging. As it charges the current drops and the voltage rises.

[David T]

A bad battery can make a good alternator look bad and a bad alternator can make a good battery look bad. They affect each other and they really should both be tested if a problem is suspected. The voltage regulator is supposed to limit the voltage to around 14.7 volts and if it is much above that you start to suspect the regulator, or possibly the battery or the connections between them. If you were cranking the life out of the battery and the car finally starts the output voltage of the alternator can be high initially but should start to come down once you get some of the charge back into the battery. Another possibility is you have one or more blown diodes in the rectifier bridge. That can be very bad for the battery if the alternator is outputting AC. Bottom line, if you think you have voltage problems you test the alternator AND the battery and all of the connections between them. If the battery is over 5 years old it should probably be replaced.

[Ron]

He already checked (replaced) the battery.....

[Michael]

He already checked (replaced) the battery.....

You can't make one sentence posts like that in the shadow of a David T reply!

[Bitsyncmaster]

Here is an interesting problem with battery/alternator. Yesterday I was in a boat with an Mercuriser outdrive. The engine would cut (die) if the power tilt button was moved and the volt gauge was pegged over 18 volts. Well turned out the battery cable fell off (boats take a beating) and the engine was running fine off the alternator (Mercuriser uses a GM engine and parts). I have not found out if the alternator is good yet but since there was no load on the alternator it probably showed that high voltage seeing peak rectified voltage.

By the way this 67 year old man could not get up on a slalom ski. Don't understand why I did it all the time 30 years ago.:shock:

[Ron]

You can't make one sentence posts like that in the shadow of a David T reply!

Sorry, ironically, I was trying to set an example and be moderate, but evidently went too far. Let me try again:


A bad battery can make a good alternator look bad and a bad alternator can make a good battery look bad. They affect each other and they really should both be tested if a problem is suspected.The battery's job is to store energy (for starting the engine later). And the alternator's job is to replenish the battery and provide an energy source for the vehicle's electrical system. Given the battery is new and starts the vehicle, and that the alternator is also new, but showing a voltage higher than the limit you say it is supposed to (below), check the fucking alternator.


The voltage regulator is supposed to limit the voltage to around 14.7 volts and if it is much above that you start to suspect the regulator, or possibly the battery or the connections between them.
14.9 is greater than 14.7, the limit -- Check the fucking alternator.


If you were cranking the life out of the battery and the car finally starts.... Evidently, the battery is doing it's job, and more. Check the fucking alternator.


the output voltage of the alternator can be high initially but should start to come down once you get some of the charge back into the battery.The fans were running, so the vehicle was running long enough get some of the charge back into the battery (actually replenish), but the multi-meter showed it was being overcharged. So, check the fucking alternator.



Another possibility is you have one or more blown diodes in the rectifier bridge. That can be very bad for the battery if the alternator is outputting AC.A "blown" diode does not conduct electricity. The output would be low instead. Contrary to a blown diode, a shorted diode allows current to flow in both directions, instead of one, which could cause the alternator to output AC. Either way, check the fucking alternator.


Bottom line, if you think you have voltage problems you test the alternator AND the battery and all of the connections between them. If you have (high) voltage problems, it's most likely the voltage regulator (which is inside the alternator.) Check the fucking alternator.


If the battery is over 5 years old it should probably be replaced.He already checked (replaced) the battery.....

:cheers1:Happy Labor Day

[Michael]

LOL...that was funny in a "Tommy Boy, get yourself a new map" kind of way.

[DMCMW Dave]

Sorry, ironically, I was trying to set an example and be moderate, but evidently went too far. Let me try again:

The battery's job is to store energy (for starting the engine later). And the alternator's job is to replenish the battery and provide an energy source for the vehicle's electrical system. Given the battery is new and starts the vehicle, and that the alternator is also new, but showing a voltage higher than the limit you say it is supposed to (below), check the fucking alternator.


14.9 is greater than 14.7, the limit -- Check the fucking alternator.

Evidently, the battery is doing it's job, and more. Check the fucking alternator.

The fans were running, so the vehicle was running long enough get some of the charge back into the battery (actually replenish), but the multi-meter showed it was being overcharged. So, check the fucking alternator.


A "blown" diode does not conduct electricity. The output would be low instead. Contrary to a blown diode, a shorted diode allows current to flow in both directions, instead of one, which could cause the alternator to output AC. Either way, check the fucking alternator.

If you have (high) voltage problems, it's most likely the voltage regulator (which is inside the alternator.) Check the fucking alternator.

He already checked (replaced) the battery.....

:cheers1:Happy Labor Day


Where is the thumbs-up button on this thing!

[David T]

Here is an interesting problem with battery/alternator. Yesterday I was in a boat with an Mercuriser outdrive. The engine would cut (die) if the power tilt button was moved and the volt gauge was pegged over 18 volts. Well turned out the battery cable fell off (boats take a beating) and the engine was running fine off the alternator (Mercuriser uses a GM engine and parts). I have not found out if the alternator is good yet but since there was no load on the alternator it probably showed that high voltage seeing peak rectified voltage.

A problem with the battery or the connections between the alternator and the battery can cause the voltage to soar. A bad voltage regulator can do it as can bad diodes. A high DC voltage can also be a sign of bad diodes and you are actually reading the DC component of a lot of AC being impressed on the electrical system. New batteries can be bad or fail. My point is any time you have to test the alternator you should also be testing the battery and vice-versa. If you do have bad diodes the battery is going to fail prematurely, they do not live long on a diet of AC. They also do not do well with too much voltage, it cooks them. Especially the new ones that aren't vented and the gell type. Yes, start with the alternator but check the battery and the connections also.

[Ron]

Here is an interesting problem with battery/alternator. Yesterday I was in a boat with an Mercuriser outdrive. The engine would cut (die) if the power tilt button was moved and the volt gauge was pegged over 18 volts. Well turned out the battery cable fell off (boats take a beating) and the engine was running fine off the alternator (Mercuriser uses a GM engine and parts). I have not found out if the alternator is good yet but since there was no load on the alternator it probably showed that high voltage seeing peak rectified voltage.Pure plagiarism. :deviltail:


A problem with the battery or the connections between the alternator and the battery can cause the voltage to soar. A bad voltage regulator can do it as can bad diodes. A high DC voltage can also be a sign of bad diodes and you are actually reading the DC component of a lot of AC being impressed on the electrical system. New batteries can be bad or fail. My point is any time you have to test the alternator you should also be testing the battery and vice-versa. If you do have bad diodes the battery is going to fail prematurely, they do not live long on a diet of AC. They also do not do well with too much voltage, it cooks them. Especially the new ones that aren't vented and the gell type. Yes, start with the alternator but check the battery and the connections also.A problem with the connections between the alternator and the battery would not allow him to crank the life out of the battery...

Changing the word "blown" to "bad" does not work... A "bad" diode is either open or shorted (to some degree, aka "leaks").

===================

Good alternator:
61068

Bad Alternators:
61069
Open Diode


61070
Shorted Diode

Note both have a lower output!

===================

If you have an open circuit between the alternator's output and battery, then the system voltage will spike (as with Dave M's boat). But the battery is not going to be overcharged -- It's disconnected!

If all of the diodes were open ("bad"), it would not cause the battery to "fail prematurely" because there would be no output.