98 V70 GLT blown fuse #5

wag-a-mo · Post by **wag-a-mo** » 16 Aug 2012, 19:18

Hello everyone. I am new to posting on this forum, however I have been coming here for answers the last few years. I have an issue that there are no discussions about.

My 98 V70 GLT is blowing fuse #5 (climate control/diagnostics). I first noticed a problem when my "park brake" light was on when my car was off. Then I noticed my a/c was blowing hot air, not just outside air but "hot". That's when I discovered the blown fuse and replaced. A/C worked for half hour with 1 OBD code P0108 (Manifold Absolute Pressure/BARO Sensor High Input) then blew again. I disconnected battery over night, replaced fuse again. A/C worked for a while then blew fuse again. No OBD codes or "park brake" light for the past few days. Checked a/c wires-good.

Thanks in advance for your suggestions
Aaron

hyp2bsqr · Post by **hyp2bsqr** » 02 Sep 2012, 22:10

I am chasing a similar problem. Unfortunately #5 controls all the major emissions circuits as well. Thus far I have unplugged the PTC and the A/C pump electric supply and have not blown the fuse again. Unfortunately running without A/C in not a great prospect.

One think I noticed as well is that under hard acceleration or quick left turn the fuse will blow if the A/C is turned on. That is why I have disconnected the A/C power feed at the pump. I had originally suspected the PTC had a short but I am not so sure. I have been chasing this for a month and have had the entire engine compartment ripped apart right to the ECU box.

As of right now I think the problem is a faulty harness, specifically where it runs across the subframe in front of the engine. No amount of manual flexing, pulling, twisting or other stress on the harness causes the failure.

If I find the root cause to the problem I will post here.

Post by **kcodyjr** » 04 Sep 2012, 13:09

Just a hunch, take a look behind/under the glove compartment. I'll bet you find one of the harness bundles has had, shall we say, a "catastrophic thermal event".

I'm assuming that the harness layout is more or less the same as in the 850 - this could be a lark.

Point is, the parking brake light being on when the car is off is a surefire sign there's a short somewhere.

wag-a-mo · Post by **wag-a-mo** » 04 Sep 2012, 18:20

Thank you both for your replies. Initially i took apart my ecu (98 T-5, bought from ebay) expecting something to be fried, but that wasn't the case. I did reinstall my stock (GLT) ecu just in case. I don't notice any decrease in hp or driving and the park brake light never came back on.

I will check behind the glove compartment as 'kcodyjr' suggested, then it will be off to my mechanic. He loves a good challenge.
If and when I get an answer, I will post.......thanks

hyp2bsqr · Post by **hyp2bsqr** » 18 Oct 2012, 13:09

So in my case (S70 GLT Sedan) it was the cross-frame harness section. In Volvo's desire to "protect" the harness they put it in a nice ballistic plastic tray. It's a nice idea in theory, but there is nowhere for oil and dirt to go but get collected in the tray. Over time the oil and dirt act as liquid sandpaper as the wires naturally rub together. This is especially true for the twisted pairs, of which there are many. Eventually you have wires crossing signals, grounds, VCC and VSS, etc - not good.

My solution was to open the tray, pull the wires out, space the wires apart by stretching perpendicular to path-flow, thoroughly clean them with CRC Brake Clean (red can, NOT green), spray the wires with wire-shellac or clear laquer and loosely tie-wrap the bundle and place on the tray. I did not close the tray up and likely will not.

So far so good. I know that I will eventually have to replace the harness if the car lives on long enough, but for now this works marvelously for my daughter's first car.

Pete

hyp2bsqr · Post by **hyp2bsqr** » 28 Apr 2013, 07:15

Follow up after 6 months and a messy winter: all is good, no issues with the wiring.