Volvo 760 abs

[cp1790]

My car failed mot this week due to there being no abs light when starting the car as well as this after the break test all breaks locked up but I put that down to the car being sat a long time and lack of use...what and where do I need to start looking at to get the bulb to illuminate and the light being dead indicates a fault somewhere so could that be a reason that all the breaks locked themselves up?

[Laird Scooby]

Originally Posted by cp1790

My car failed mot this week due to there being no abs light when starting the car as well as this after the break test all breaks locked up but I put that down to the car being sat a long time and lack of use...what and where do I need to start looking at to get the bulb to illuminate and the light being dead indicates a fault somewhere so could that be a reason that all the breaks locked themselves up?

What year is your 760, what engine/body/transmission and is this the first MoT in your ownership of it?

Does the speedo work and do you recall the ABS light ever working since you've owned it? Also, when was the brake fluid last changed?

Just a few questions to start ^^^^^ with, will be loads more, hopefully something as simple as a blown fuse or two and perhaps a blown warning light bulb as it should light up during the self-test of the other warning lights.

[volvo again]

Does the light actually illuminate when you turn ignition on ?
Could be simply a blown bulb...
Or...a previous owner removed the bulb, in which case.....why??

[Laird Scooby]

Originally Posted by volvo again

Does the light actually illuminate when you turn ignition on ?
Could be simply a blown bulb...
Or...a previous owner removed the bulb, in which case.....why??

No, but that's not the only fault. The brake fluid is in excess of 2 years old from the sound of things and hasn't been changed so is likely full of air that would have got compressed during the brake roller test on the MoT and then held the brakes on until it dissiated through the system again.

Two or three fuses on the system, depending on the year, if the old brake fluid is contaminated with air that means there will also be moisture in it that may have killed the ABS modulator pump and possibly the modulator block too.

[cp1790]

still not got to the bottom of this if anyone else has any input iv put new bulb in cluster to find I still have nothing..but iv fount the over voltage relay with the 10amp fuse to find that has blown I thought changing it would be the problem but still getting nothing coming on the cluster,,so the things left are relays and sensors now also the abs module but I’m thinking that the over voltage relay could be shot if it’s got hot enough to blow the fuse

[Laird Scooby]

Originally Posted by cp1790

I’m thinking that the over voltage relay could be shot if it’s got hot enough to blow the fuse

It's not a thermal fuse. If the relay had got hot enough to melt the fusible link in the fuse, the car would have been on fire and would have melted the plastic of the over-voltage relay. Something as simple as jump starting can pop an over-voltage relay fuse.