Alternator Repair & Replacement
Also called charging problem
The alternator charges the battery and runs the car's electrics once the engine is running. When it fails you get a battery warning light, dimming lights, and a battery that goes flat within a day or two. Repair may mean brushes, a regulator, a rectifier or bearings; sometimes replacement is the better value. We test charging voltage and output before deciding. A new alternator will not fix a flat battery caused by a parasitic drain or a battery that is already dead.
Signs you need this
- Battery or charging warning light on while driving
- Headlights dim at idle and brighten when you rev
- The battery goes flat overnight or within a couple of days
- A whining or grinding noise from the alternator
- Burning smell from the alternator area
Not all of these have to be present, and one of them on its own can mean something else entirely. That is what the diagnosis is for.
What the job includes
- Charging voltage measured at idle and under electrical load
- Battery tested first, so a failed battery is not blamed on the alternator
- Drive belt and pulley checked for slip and bearing noise
- Alternator output and ripple tested before removal
- Repair of brushes, regulator, rectifier or bearings, or replacement where economic
- Charging rechecked with headlights, blower and rear demister on
How we do it
Test the battery first
A load test on the battery comes first, because a dead battery and a dead alternator produce the same complaint.
Measure charging voltage
Voltage is measured at the battery at idle and at raised engine speed, with and without electrical load applied.
Check belt and wiring
A slipping belt or a corroded main output cable can cause undercharging with a perfectly good alternator.
Repair or replace
Where brushes, a regulator or bearings are the fault we repair; where the unit is worn out we quote replacement.
Retest under load
Charging is confirmed with headlights, blower and demister on, which is when a weak alternator shows itself.
How we work
The same on every job, which is why we can write it down.
Diagnosis before quote
We find the fault first. A price given over the phone for a noise nobody has heard is a guess.
The price is agreed first
You approve the work and the cost before a spanner is picked up. Extra work means another call.
Parts you can check
We tell you whether a part is genuine, OEM, aftermarket or used, and what each one costs.
Old parts returned
Ask and we will hand back whatever we replaced. It is the simplest proof that the job was done.
Book alternator repair & replacement
Fill this in and a person will call you back to confirm the time and the price. Only your name and one way to reach you are required.
You send this
Takes a minute. No payment, no obligation.
We call you
To confirm the car, the time and the location.
Tell us the car and the symptom
We will arrange a mechanic at your location, or a slot at the nearest workshop. No payment until the price is agreed.