IPD sale XeMODeX - Experts in Volvo Electronics
Did you know? 🤔
Logged in users can get email notification of topic replies Log in or register (free).
Amazon Link Buy anything with this and it helps MVS!

1999 S70 headlamp voltage question

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

Mirrored
Posts: 4
Joined: Fri Mar 13, 2020 5:33 am
Year and Model: 1999 S70
Location: Missouri
Has thanked: 0
Been thanked: 0
United States of America
Mirrored

1999 S70 headlamp voltage question

Post by Mirrored » Fri Mar 13, 2020 5:46 am

Hello all, I have a question about the headlights on my 1999 S70. I had this car given to me by my dad 6 months ago. Not long after I got it, I noticed a headlight pretty dim. After investigating, one of the low beam sockets was pretty smoked, so I decided to buy new headlight assemblies, both sides. All has been fine until recently, my wife was driving behind me and the low beams were bright as a heck. So much so I called to ask if the high beams were on, so she flicked the highs on to show they were not. I checked voltage at one of the bulbs and saw 14.4 vdc. The car had an alternator replaced a couple months before I got it. Seems like high voltage to the low beam bulbs? Sorry for the long winding posted, but any input is appreciated, thanks.

User avatar
abscate
MVS Moderator
Posts: 21084
Joined: Sun Feb 17, 2013 5:54 pm
Year and Model: 99T5 ,99S70,2005V70
Location: NYC, ALBANY NY
Has thanked: 318 times
Been thanked: 982 times
Trinidad & Tobago
abscate

Re: 1999 S70 headlamp voltage question

Post by abscate » Fri Mar 13, 2020 5:49 am

That does sound a bit hot. How old is the battery on the car? If it is weak, the alternator might be pushing hard to try charge it and running the voltage up higher.

Most of us are surprised how bright our lights are when we replace the 20 year old reflectors, though
Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
Link to Maintenance record thread
Link To Volvo Glossary

Mirrored
Posts: 4
Joined: Fri Mar 13, 2020 5:33 am
Year and Model: 1999 S70
Location: Missouri
Has thanked: 0
Been thanked: 0
United States of America
Mirrored

Re: 1999 S70 headlamp voltage question

Post by Mirrored » Fri Mar 13, 2020 5:51 am

The battery is pretty new also, about 1 year old.

User avatar
abscate
MVS Moderator
Posts: 21084
Joined: Sun Feb 17, 2013 5:54 pm
Year and Model: 99T5 ,99S70,2005V70
Location: NYC, ALBANY NY
Has thanked: 318 times
Been thanked: 982 times
Trinidad & Tobago
abscate

Re: 1999 S70 headlamp voltage question

Post by abscate » Fri Mar 13, 2020 5:54 am

Try comparing lights with engine off, key in POS II, and then running. Check voltage at lights under same conditions.

If you alternator is overcharging you want to deal with it as it can cook the battery if you run it for months like that. Concern, not panic.

The voltage from the alternator might spike after a start if the car has been sitting, to recharge the battery. Maybe do the above checks after a 30 minute drive to see if it changes?
Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
Link to Maintenance record thread
Link To Volvo Glossary

Mirrored
Posts: 4
Joined: Fri Mar 13, 2020 5:33 am
Year and Model: 1999 S70
Location: Missouri
Has thanked: 0
Been thanked: 0
United States of America
Mirrored

Re: 1999 S70 headlamp voltage question

Post by Mirrored » Fri Mar 13, 2020 5:57 am

Thanks abscate, I will check that tonite when I get home from work.

Mirrored
Posts: 4
Joined: Fri Mar 13, 2020 5:33 am
Year and Model: 1999 S70
Location: Missouri
Has thanked: 0
Been thanked: 0
United States of America
Mirrored

Re: 1999 S70 headlamp voltage question

Post by Mirrored » Fri Mar 13, 2020 7:47 pm

Ok here are some numbers:
Key off, VDC at battery-12.2
Key in position 2, VDC at low beam bulb-11.7
Car started, VDC at battery-14.4
Car started, VDC at low beam bulb-14.4
After 45 minutes drive, VDC at low beam bulb-13.95

I guess the question is the voltage regulated down before it hits the low beam bulb? I have yet to look for a schematic to see if this is the case.

Post Reply
  • Similar Topics
    Replies
    Views
    Last post