No charge for 1st few minutes in the morning...

[Teessider]

Got a strange long term problem with my electrics...this has been ongoing for about 2 years!

A couple of years ago, first thing on a morning, or after the car (1993 Toyota MR2) had been stood for hours, when I first started, a number of dashboard lights would illuminate and the battery meter would read lower than usual...essentially the alternator wasn't charging the battery.

After a mile or so, the dash lights would go out and charging would return to normal...

Eventually, one day the alternator burnt out in a puff of smoke and I had it renewed...the problem, at first seemed to go away but a few weeks later was back. As usual, as it always started charging, I just ignored it =D

Anyway a week ago it stopped charging altogether and another new alternator was diagnosed as the problem. I got my car back yesterday and again, its gone back to not charging for a few minutes after first starting, then righting itself after a few minutes!

Obviously another trip to the garage is in order but unless he catches it while its not charging, he wont find a fault...and if he doesn't solve it within the first few minutes of starting it, it rectifies itself...at that rate it could be in the garage for ages!

Anyone come across this sort of thing before? Any ideas? Only thing I could think of that only operates for a few minutes is *maybe* the automatic choke?? But of course, im not auto electrician!

Thanks in advance! =)

 

[waross]

If the voltage regulator is external to the alternator, change the voltage regulator.
Loose drive belt? Are you able to turn the alternator by hand in both directions? When the belt is tight enough, expect the alternator to be very difficult to turn manually. Many alternators may be turned in one direction only with difficulty and you may not be able to turn it in the opposite direction.
A loose belt will slip and generate heat. The heat will often destroy the drive end bearing but may also lead to the destruction of the winding.
If this is the case, expect to encounter denial.
I checked a belt drive alternator where the drive end bearing was failing frequently. The belt was too loose but the customer swore that the belt didn't need to be any tighter and would not increase the tension. He blamed bad bearings.... like six or eight times.
Try another shop.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[patprimmer]

Lose belt or bad earth or hot connection somewhere between the alternator and the battery.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Teessider]

Thanks for the replies...

Already had 2 different mechanics do the alternator, and tightened the belt. I can also see the alternator pulley and belt while the engine is running and all seems to be fine.
Also, if it was a loose belt - would it not happen randomly, and not just after being stood for a number of hours?

Not sure about the voltage regulator, I'll look into that.

A bad or intermittant earth would also be random, would it not? Unless of course, expansion of some part as the engine gets warm is just enough to remake the connection...

I can see this one dragging on for a while! Thanks for the pointers =)

 

[patprimmer]

The alternator load depends on recent battery drain and temperature.

Sometimes heat from arcing improves a connection.

This is an old car. 90% of electrical problems that persist when major components bench test OK are earth problems.

First step, back off and re-tighten all connections. To take it one step further remove screw or nut and install a feather washer between the connector and the body (that is the body, not the nut).

Next step, inspect connection between wires and connectors and clean and solder as required. If a drop of salt water or acid on the crimped area of the connector/wire interface improves it, solder will fix it. Check for fatigue cracks in the copper strands at the edge of the connector.



Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Teessider]

Thanks for your help, I'll go through this step by step and an earth does seem to make sence, espcially as you mention heat from arcing improves connection...this would seem to tally with what is happening.

 

[evelrod]

Interesting. I use an ND from a Toyota, 90ish era in my Mini Cooper race car. I've had no problems in nine years.
I don't know if mine is the same as yours, but if it is, there is only the one hot lead to the little 6mm stud on the top of the alternator. The other connections are on a plug in module, one 12v and one for an indicator light both in one plug-in. Pretty easy to have one of the plug in parts fail to make good contact. In my case, I 'hard wired' these connections and then 'potted' the plug in module.

Once a long time ago when alternating current generators were first beginning to make more common appearance on road cars, I had a similar series of failures...change gen., change reg., belts, etc. The usual suspects. Turned out to be a 'shorted' battery.

Rod

 

[LionelHutz]

Check the charging indicator light circuit. It's often used to provide enough field current to start the alternator.

 

[WhizzMan]

Indeed, the charging light circuit is something to look at.

Also, the MR2 is a mid-engined car that is notorious for water damage to the alternator and it's wiring. It seems that water coming from the roof and engine cover will drip on the alternator and it's surroundings, so corrosion to both the wiring and the bearings of the alternator is often a reason for the alternators needing replacement. This is at least true for the first generation of MR2, I don't know if newer versions still have this.

 

[dgallup]

1993 MR@ was the 2nd generation (the good looking one). I don't think it shared anything but the name with the first generation.

 

[zzzjim]

A recent battery of mine was collapsing to 11V on starting
(1 Cell acting like a SWITCH )
then taking a little time before it became 12V (6-cell) battery instead of a 10V read 11.5v (well charged,5-cell)

Consider checking with another borrowed battery !

Modern calcium batteries do seem to have "Extra features"

 

[MRSSPOCK]

I had a weird problem which took about three years to find, only it was the inverse. But like LionelHutz said, that was my problem. The charge warning light circuit, (in my case at least), is used to create the self excitement within the alternator to initialise charging.

On firing up a cold car, mine was initially charging fine, but when the dashboard warmed up, the warning light circuit became open circuit. The car would continue to charge fine as long as the engine remained running. If I stopped the engine and started it immediately, it wouldn't charge. If I let the dashboard cool down, then restarted, it self excited again okay, and it would charge again.

Could it be the opposite in your case, i.e. the warning lamp circuit is open initially, but with expansion due to heat, the open circuit is becoming closed, and charging begins?

My problem was a nick in the printed circuit behind the instrument panel. (See attachment)

 

[gordguide]

This is probably unrelated to your problem, but I'm going to throw it out there anyway.

According to the description by evelrod, the installed alternator seems to be of the "1-wire" type (with internal regulator). This is the standard style alternator used by GM vehicles for many years.

These alternators do not charge until the RPM level reaches a certain point, but unlike some others, will continue to charge (at a low rate, since it's RPM dependant) after the car is started and that RPM level is reached (ie when you idle down).

If that is the case with the MR2 design, then it's good practice to blip the throttle on startup once the engine has reached a safe oil pressure level. This instigates charging during warmup. With the GM alternators, you need to have the engine go above about 1600~1800 RPM.

 

[Vestedjoe]

Take a look at this explanation:

http://vestest.com/MultipleAlternatorReplacement.pdf

Joe

 

[Gearloose1]

If there is a sense wire (for battery voltage) going from battery to alternator, replace the alternator pigtail.

There can be an internal break that is intermittent, that will work once it is "heated" but not before.

Also, clean all contacts, ground wires, and check for corrosion related issues.

 

[kontiki99]

Could be an indication problem and not a charging problem. All of which can be verified by temporarily hooking a volt meter to battery terminals and watching volage as you drive.

Voltage regulators control the field to the alternator, that is how charging is controlled.

 

[msquared48]

Whenever I change an alternator, I always change out the voltage regulator too. No exceptions, good or bad.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[drwebb]

I know some mechanics that sometimes look a little "worse for wear & tear" when they first get to work- I wish THEY'D give me no charge for 1st few minutes in the morning!

 

[evelrod]

Bad experience lately?

Rod