high beam fuse problems

[gazdkw82]

I have a recently new to me 2008 Volvo xc70. After a day or so I noticed the main (high) beam wasn't working. At first I suspected blown lamps so I inspected and they seemed fine. Replaced fuse and all was good for a day, fuse blew again. Replaced lamps as a next step and replaced fuse. Lasted a day again. Initially it works fine, I even left the high beam on for 10 mins or so. Then when I came to use it the next day the fuse instantly blew, as if a short.

Yesterday I unplugged the lamps from the holder and replaced the fuse. Again, lasted a day or so.

The confusing bit is, if it was a short or earth fault id imagine it to be happening straight away, not work initially then randomly blow the fuse.

I'm abit stumped now. I'm thinking maybe I should investigate the relay?

any help would be appreciated

 

[DPG]

Could be an intermittent short. I once repaired a Sierra which was blowing a fuse but only intermittently. Had been in garage twice but still not cured. Eventually traced it (by spiking the suspect wire and leaving a continuity tester connected between that and earth whilst doing the wiggle test) to inside the two skins of the rear of the car where over the years the wiring harness had been rubbing against the metal work. It had gone through the harness tape and then through the insulation of the wire - every so often it would make contact and blow the fuse.

Took me nearly a full day to track that down. Had to remove driver's seat and various bits of trim, carpet etc.

 

[Deleted member 26818]

Sounds like faulty wiring, though it could be a faulty relay.

 

[gazdkw82]

Sounds like faulty wiring, though it could be a faulty relay.

How do you go about testing a relay?

 

[telectrix]

can't se it being a relay. more likely as DPG says. intermittent short on the wires from relay to lamps. orrrrr...have there been any spots fitted. coming on with high beam?

 

[DPG]

Unlikely to be the relay, although not impossible. Very easy to swap it out to prove though. Or get it on the bench and set it up with a feed to the coil, and some sort of load (lamp etc.) through the contacts.

 

[static zap]

If its old school -Lo Tech Stalks ,feeling a bit wobbly!
(Check don't have a Horn + Flash MB on same stick) ...Old ways..

 

[gazdkw82]

It's not an old vehicle (2008)

I don't think there is any additional spots added or any other adjustments/additions.

When it does work the relay does sound fairly loud

 

[ruston]

As it is new to you , has it got the correct bulbs in , or cheap tatty replacements?

 

[ruston]

Also go onto the Gov site and check the MOT history of failures to see if this is an ongoing problem . You may of bought a known ongoing fault.

 

[gazdkw82]

I changed the lamps for another brand new set I had.

Chances are slim that it's a lamp issue

 

[ruston]

I've seen a lot of fuse failures caused by poor quality lamps and holders . it is quite common . especially helped out by corrosion.