Alternator Repair & Replacement
The alternator is the small generator driven by the engine belt that powers every electrical load once the car is running and recharges the battery. When it fails, the car runs on stored battery power until that is gone, then stalls, often without much warning. A proper test separates a failing alternator from a tired battery.
From AED 449Written quote after diagnosis, before work startsConvenience fee applicable · shown on your written quote
- 1-3 hours for most cars; longer when the alternator is buried
- Pickup and delivery from your door
- Convenience fee applicable · shown on your written quote
- Diagnosis free with repair
Signs you need alternator repair & replacement
- Battery warning light glowing on the dash while driving
- Headlights and dash lights that dim at idle and brighten when you rev
- A new battery that goes flat again within days or weeks
- Whining, growling or grinding from the front of the engine that follows the revs
- Smell of hot rubber or a squealing belt, particularly when the AC compressor engages
- Power windows slow, infotainment rebooting or random warning lights across the cluster
What usually causes it
Worn carbon brushes and slip rings
Brushes carry current to the spinning rotor and wear down like pencil lead. Once they are short or the slip rings are scored, output becomes erratic or stops altogether. This is the most common repairable fault.
Failed rectifier diodes
The alternator makes alternating current, and a bank of diodes converts it to direct current. A dead diode cuts output, and leaked AC ripple can upset the car's computers and drain the battery overnight.
Voltage regulator fault
The regulator decides how hard the alternator charges. If it fails low the battery starves; if it fails high the battery boils and bulbs and electronics are at risk.
Bearing, belt or pulley trouble
A dry bearing growls and eventually seizes, and a slipping belt or failed overrunning pulley stops the rotor from spinning at the right speed. These are mechanical problems that look like electrical ones.
How we do alternator repair & replacement
- 1
Battery and charging output test
We test the battery first, then measure charging voltage at idle and at raised revs with lights, fan and rear screen switched on. A healthy system holds roughly 13.8 to 14.7 volts.
- 2
Ripple and voltage-drop checks
A meter or oscilloscope shows diode ripple, and voltage drop tests along the output cable and earth strap reveal corroded connections that mimic a dead alternator.
- 3
Belt, tensioner and pulley inspection
We check belt condition and tension, and spin the pulley by hand for roughness and a failed freewheel clutch before removing anything.
- 4
Repair or replace
Brushes and regulators can often be replaced individually. If the unit is worn throughout, we fit a new or reconditioned alternator, coded to the car where the charging system requires it, then retest output.
In Dubai, Sharjah and Ajman
Alternators here run hot and hard: 45 degree under-bonnet temperatures, the AC compressor on, headlights and seat cooling all at once while stuck in traffic with low engine revs and low alternator output. That combination shortens brush and diode life compared with milder climates, so a weak battery and a tired alternator often fail together.
Questions about alternator repair & replacement
How do I know it is the alternator and not the battery?
A battery that starts the car after a jump but is flat again the next day may be fine and simply not being charged. We load-test the battery and measure charging output, which settles it in minutes.
Can I drive to you with the battery light on?
Only for a short distance, with non-essential loads switched off. The car will stop once the battery empties, which can happen on a motorway. Call us and we can arrange pickup and delivery instead.
Repair or replace?
Replacing brushes or a regulator is cheaper and suits an otherwise healthy unit. A noisy bearing plus worn slip rings usually justifies a replacement. You see both prices when both are realistic.
Are reconditioned alternators any good?
A reconditioned unit with new wear parts is a reasonable middle choice between new OEM, aftermarket and used. The parts choice is yours and the price of each is on the written quote.
Will the new alternator need coding?
On many newer cars with smart charging the alternator communicates with the engine computer and must be matched after replacement. We do this where it is required.
Last updated
Get a written quote
Tell us about your car. You get an itemised quote before any work starts, and you choose OEM, aftermarket or used parts.