2000 S70: Wiper fuse keeps blowing, despite new motor

Zoidberg · Post by **Zoidberg** » 27 Sep 2013, 06:12

I'm wondering if anybody has some insight into the problem I've been having for the past couple of weeks. Personally, I hate dealing with electrical problems, since they're tricky to diagnose and have a habit of disappearing when you're trying to replicate the problem...

Here's whats been happening:

A couple weeks ago, I turned on the car and as I tried the wipers, nothing happened. I checked the fuse box, and sure enough the fuse (25 amp) was blown, so I replaced it with a spare. Problem solved, right? It worked for a few days just fine, until I was driving and used my wipers, and they died right while in use. Blown fuse again. I figured there must be something seriously wrong, so I checked all the connections, both to the switch and to the motor, but everything looked fine.

I took the car to a garage that I trust, they examined the whole system, and their diagnosis was that the wiper motor was drawing too much current and therefore blowing a fuse. Their recommendation was that I replace the motor. Since new ones from the dealer go for nearly $500, I shopped around and got a used one from a recycler for $50. I installed it myself and everything seemed to work great for a few days, until the fuse blew again...

I took the car back to the shop and they tested the current draw, but even with the wipers on full, with the washer going, it wasn't drawing anywhere near the maximum. I should add at this point that I have had the headlight wiper motors unplugged for several months, so they're not part of the equation. The mechanic also tested the connections by testing current draw while moving the steering column around and pulling on all the wire harnesses. He couldn't find a fault, so in the meantime, he installed an automatically resetting fuse, so at least I wouldn't be stranded without wipers.

That was yesterday afternoon. This morning, my wipers worked fine (I only used them briefly when I first started out), but after about 5 minutes of driving, I had a significant electrical failure! It looks like a larger fuse on a bigger circuit failed, because here are the systems that turned off:

Radio
SRS (the warning light came on)
headlights, foglights
dash lights (however, the trip computer still worked)
turn signals (hazard flashers still worked, interestingly enough)
wipers
climate control system

This is so frustrating! Where should I look next? My thought is maybe it's the climate control system causing some transient current spike or something, since my electrical failure ocurred right about when the climate control fan (it's set to auto) would have turned on...

Thanks for any help or advice you may have

Zoidberg · Post by **Zoidberg** » 27 Sep 2013, 06:15

Oh one more thing... I also pulled the relay and pulled the cover off. Nothing appears burnt or overheated, and there's no "burnt electronics" smell...

I also just opened up the fuse box, and in the auxiliary fuse box nothing is blown, but in the "Main Fuses" box, I blew a 50A fuse (fuse #2, going to the auxiliary box)... That would explain why some systems weren't working, but doesn't explain the why it blew...

Deddy425 · Post by **Deddy425** » 03 Jan 2017, 00:00

Hello I was just wondering if you ever found out why it keeps blowing the fuse? I am currently having this problem on a 98 v70 wagon. I have tried numerous things and nothing seems to work. Any help would be greatly appreciated! Thank you

Post by **abscate** » 03 Jan 2017, 05:17

This isn't difficult, but requires systematic wiring examination. Obviously there is a short between the 50 amp fuse and the wiper motor. You get the wiring diagram and trace the wires.

There isn't a " common place" or mode of failure for this, it's very rare, unlike the rear wiper.

Post by **scot850** » 03 Jan 2017, 11:32

abscate is correct in advising the wiring inspection and test route as he is a wise man!

I'd also check in the main fuse box for a melted or shorting B+ cable. Open the top of the kidney shaped fuse box in front of the brake booster and looking down into it look at the front end at the nut and cable there carefully. The cable end should be shiny as should the nut. If it is discolored or the cable below the nut is burnt it can short to ground.

Next point to look would be the lever for the wiper on the steering column. The wire can chafe and fracture over time. You would need to remove the column cover and remove the arm to give it a good inspection.

: B+ cable at main fuse box (removed from car)

: B+ cable at main fuse box (removed from car (2)

Neil.

Post by **sleddriver** » 04 Jan 2017, 13:22

Deddy425 wrote:Hello I was just wondering if you ever found out why it keeps blowing the fuse? I am currently having this problem on a 98 V70 wagon. I have tried numerous things and nothing seems to work. Any help would be greatly appreciated! Thank you

If any of the wire insulation has degraded, you'll have a place for a short to occur. As the wiring warms up due to either cabin heat or engine compartment heat, it will expand. Add in vibration from road, engine, etc. and the wires will rub together.

The problem is tracking these shorts down. Wiring diagram is the first step. Then locating the correct connectors on/in the car. ID'ng the wire colors, then going from there.