Car electrics question

[Henry Mydlarz]

My daughter has an old 1.3 litre engine Ford Laser. The idle speed is normal
until the headlights are turned on. Then it drops by about 20%. When the
brake lights come on there is a further drop in idle speed, until the engine
occasionally stalls. Having dabbled in car engine repair and car electronic
repair I have never come across this. Can this be an alternator problem
where it puts too much load on the engine under heavy current? If so, what
would it be about the alternator that would cause this? Can it be a
non-electrical problem?

Thanks for any advice.

Henry.

 

[Chris Prestwich]

My daughter has an old 1.3 litre engine Ford Laser. The idle speed is normal
until the headlights are turned on. Then it drops by about 20%. When the
brake lights come on there is a further drop in idle speed, until the engine
occasionally stalls. Having dabbled in car engine repair and car electronic
repair I have never come across this. Can this be an alternator problem
where it puts too much load on the engine under heavy current? If so, what
would it be about the alternator that would cause this? Can it be a
non-electrical problem?

All earthing OK? Clean and tight connections, battery fully charged,
electrolite levels up?. Specific gravity OK?

Thanks for any advice.

No problemo.

__ __ __ __ __
Regards, Chris
[spamblock used]

 

[Razor's Edge]

Henry,

The ECU will automatically adjust the idle rpm when electrical loads are
connected / disconnected.
This is done by a special idle control valve that its placed near the
throttle on the intake.
They use to have a stepper motor to control the on/off time of this valve
making it kind of PWM.

Regards
Stefan

 

[Henry Mydlarz]

Thanks Stefan,

Although this 1982 car doesn't have any electronic ECU, I would bet that
there is some such mechanical compensating control which is probably not
functioning. Unfortunately the rather basic repair manual does not fully
describe such operation or all the aspects of the carburettor. Well, now I
know what to look for. Your information is very logical.

Thank you once again.

Henry

 

[Loren Coe]

rec.autos.repair is one of the best ng's extent, they likely will help
you. try xposting w/followups to one group. --Loren

err, i meant rec.autos.tech, also, rec.autos.ford, --Loren

 

[Bob Minchin]

ALTERNATOR!!! Seems like it's going bad slowly. Cheap and easy fix!

Why should it be the alternator? A failing alternator would generate less power
and put less load on the engine surely?
I'd suspect the timing and or carburator settings. The OP did not say if the car
runs ok in normal driving.

Bob in UK

 

[Henry Mydlarz]

There is a diaphragm at the carburettor which is meant to increase the idle
speed when electrical load is applied. The vacuum going to the diaphragm is
turned on/off by a "three way solenoid". On another car I looked at, with
the exact same setup, 12VDC is applied to the solenoid when the air
conditioner is on. That allows vacuum into the idle diaphragm, increasing
the idle speed. On the faulty car, 12 VDC is applied constantly, but no
vacuum is applied to the diaphragm. At least now I know what the problem is.
All I have to do is understand how that dratted valve is supposed to work,
and what activates it.

Anyway, this may be a more appropriate question for a motoring newsgroup, so
sorry for the diversion.

Henry

 

[Jim Adney]

My daughter has an old 1.3 litre engine Ford Laser. The idle speed is normal
until the headlights are turned on. Then it drops by about 20%. When the
brake lights come on there is a further drop in idle speed, until the engine
occasionally stalls. Having dabbled in car engine repair and car electronic
repair I have never come across this. Can this be an alternator problem
where it puts too much load on the engine under heavy current? If so, what
would it be about the alternator that would cause this? Can it be a
non-electrical problem?

Most modern cars have what is called an "Idle Stabilizer" which is a
valve which tries to respond to changes in the idle speed to help keep
it constant. Adding more electrical draw to the system naturally asks
the alternator to put out more current which will always pull the idle
speed down. This is much more likely to be noticable in a 1.3L engine
than in a 4L engine, which may be what you're more used to.

Try to find the idle stabilizer and see if it is working. As another
poster mentiond, it us usually a PWM type of device.

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