Dim head lights

So I've been dealing with some electrical issues due to a dead alternator. After replacing the alternator I noticed that the headlights were still dim.

I measured the voltage at the bulb socket at 10.7v

I checked all the grounds anyway, so in good condition.

I was wondering where else could I look to get the voltage back up to normal.

Thanks.

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With the car running check the voltage on the back of the new alternator at the stud. It should be 13.5-14.5 if it’s less, take it back where you bought it and get a replacement. You almost certainly got a bad rebuild.

However if the alternator is putting out the voltage I indicated then with the car still running check the voltage at the battery the alternator and the battery should be reading exactly the same.

If the battery is not reading the 14 or so volts coming from the alternator you’ve got a bad cable.

My money is on the crap reman alternator, a new or reman Bosch is the only thing you should put on these cars.

Voltage at the alternator, battery and any other electrical system is 14.1v

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Well I guess the internet guess of a bad alternator was way off. 14.1 is perfect, you will need to track down where the drop off in voltage occurs. Start with the headlight fuses at the fuse panel. They should be fuses 18,19,20,21 .


http://fusesdiagram.com/wp-content/uploads/2017/01/EN-Golf4-blok-salon-3.jpg


codes as follow.
F1 (10A) Heated wind screen washer jets, heated door mirrors, glove box lamp
F2 (10A) Indicators, head lamp adjustment (gas discharge head lamps)
F3 (5A) Fog lamp relay, lights
F4 (5A) Licence *plate lamps
F5 (7,5A) Air-conditioning (AC),heated seats, cruise control, convenience equipment, engine coolant blower motor control module, parking aid, multifunction steering wheel
F6 (5A) Central locking
F7 (10A) Reversing lamps
F8 (5A)Telephone
F9 (5A) Electronic stability programme (ESP), Haldex coupling (2001^), anti-lock brake system (ABS)
F10 (5A/10A/15AEnginemanagement
F11 (5A) Instrument panel, AT selector lever lock
F12 (7,5A) Data link connector (DLC), telephone(^04/99)
F13 (10A) Stop lamps
F14 (5A/10A) Interior lamps, central locking
F15 (5A) ESP (05/99^), instrument panel, automatic transmission (AT)
F16 (10A) AC compressor clutch, engine coolant pump motor, engine coolant blower motor control module
F17 (7,5A) Door lock barrel heater (^04/99)
F18 (10A) RH headlamp- high beam
F19 (10A) LH headlamp-high beam
F20 (10A/15A)RH headlamp-low beam, head lamp adjustment
F21 (10A/15A) LH headlamp-low beam, headlamp adjustment
F22 (5A) RH side/tail lamps
F23 (5A) LH side/tail lamps
F24 (20A) Wind screen wash/wipe system
F25 (25A) AC/heater blower motor, air conditioning (AC)
F26 (20A/25A) Heated rear window
F27 (10A/15A) Rear screen wiper
F28 (15A) Fuel pump
F29 (10A/15A) Engine management
F30 (20A) Sunroof
F31 (20A) Brake assist (05/99^), automatic transmission (AT)
F32 (10A/15A) Engine management
F33 (20A) Headlamp washers
F34 (10A) Engine management
F35 (30A) Trailer socket
F36 (15A) Front fog lamps, rear fog lamps
F37 (10A) Audio unit, convenience equipment, navigation system (05/99^), S-contact
F38 (15A) Boot lid/tail gate lamp, central locking, convenience equipment, remote fuel flap/boot lid/tailgate release
F39 (15A) Hazard warning lamps
F40 (20A) Horn
F41 (15A) Cigarette lighter
F42 (25A) Audio unit, audio unit output amplifier, navigation system
F43 (10A) Engine management
F44 (15A) Heated seats
/
*
Relay box*is under the panel on the left side of the instrument Volkswagen Golf 4.
1 (53) Horn relay
2 (18/100) Ignition auxiliary circuits relay
3 –
4 (409) Fuel pump relay/engine control (EC) relay
5 (192/377/389) Wind screen wash/wipe intermittent relay
6 (192/377/389) Wind screen wash/wipe intermittent relay
7 (94) Throttle motor relay (^04/99)
8 (53) Heated door mirrors (05/99^)
9 (53) Fuel pump relay (4WD Diesel),l
10 (180) Glow plug relay (some models)
11 (175) Starter motor inhibitor switch relay/reversing lamps relay (some models
12 (109) Engine control (EC)relay(Diesel)
13 (53/181) Engine coolant blower motor relay (^04/99)
14 (53) Fog lamps relay (^04/99)
15 (79/407) Boot lid/tail* gate release relay
16 (185) Starter motor inhibitor switch relay (some models)
17 (53) Fog lamps relay (05/99^)
18 (450) Steering wheel multifunction control module (05/99^)
19 (450) Steering wheel multifunction control module(05/99^)
F1 –
F2 (30A) Electric windows(some models)
F3 (15A) Alarm system (indicators)
F4 (15A) Alarm system horn
F5 –
F6 (30A) Seat adjustment
F7 –
F8 (30A) Electric windows circuit breaker (some models)
*

Just for kicks have you checked the grounds on the fire eall and below the air box?

Battery compartment, firewall and under air box as well as under the steering fluid container... All check out.

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If you get 10.7 from bulb to battery terminal, its not a ground problem. I wonder if you're stuck in the DRL (daytime running light) position or your switch isn't working.

If you pull the DRL relay and the headlights go out, they are not being switched on except through the DRL circuitry. Its relay 173, shown in this thread:

http://forums.tdiclub.com/showthread.php?t=245377

johnboy00 said:

If you get 10.7 from bulb to battery terminal, its not a ground problem. I wonder if you're stuck in the DRL (daytime running light) position or your switch isn't working.

If you pull the DRL relay and the headlights go out, they are not being switched on except through the DRL circuitry. Its relay 173, shown in this thread:

http://forums.tdiclub.com/showthread.php?t=245377

Click to expand...

That was my thought as well but I thought that DRL voltage should be 11.7v.

Anyways, I pulled thy remalay, same thing. Difference between DRL and lights on is 0.5v which is really low.

I've heard that the lines deteriorate over time but that just doesn't make any sense. I'm thinking of measuring resistance between the plug and the battery but I have no idea what the normal parameters should be.

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Yes, it's affecting both sides... I'll start tracking that down.

Thanks for the help

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QuickTD said:

If you're dropping nearly 4 volts at a headlight current of 5amps each, that's 40 watts of power being lost. Something is going to be real hot somewhere... Does the problem affect both sides? If so, I would look for a hot load reduction relay in the fuse relay panel. The headlight circuits diverge at the fuse panel, so if it affects both, it is in the switch or the load reduction relay or some associated feed or ground wiring.

Click to expand...

Do you know the relay number for that one?

Also, I've been wanting ti get rid of DRL, would just pulling that relay cause any harm?

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If I recall the load reduction relay is 100.

I was thinking about this, have you reved the engine while checking the voltage output at the alternator stud. This could still be a bad alternator, that’s functioning fine at idle but doesn’t keep charging as the rpms increase.

Tdijarhead said:

If I recall the load reduction relay is 100.

I was thinking about this, have you reved the engine while checking the voltage output at the alternator stud. This could still be a bad alternator, that’s functioning fine at idle but doesn’t keep charging as the rpms increase.

Click to expand...

Yeah, but even if that is the case wouldn't the voltage be accurate but the amperage low? Also, won't that mean that after a long drive the battery would be depleted? It's at 12.65v after driving the car over 2 hours on the freeway

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12.65 is about as good as it gets so obviously it’s charging properly. It looks like your going to have to get your multimeter out find where the voltage drop is occurring.

Tdijarhead said:

12.65 is about as good as it gets so obviously it’s charging properly. It looks like your going to have to get your multimeter out find where the voltage drop is occurring.

Click to expand...

Yeah... I'm going to replace some relays and try to see if that might help... Had a couple fail in the recent past, it's 14 years old and 200k...might be time.

Then it's on to the voltage leak.

I'll keep everyone updated.

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