99 S70 GLT cranks but will not start Topic is solved

[Cricket502]

Another thing worth asking about is, how old is the contact block on
the end of the lock cylinder. Was it replaced along with the cylinder?

And one more question about the shop - Are they a reputable dealer
or indy specializing in our older P80 Volvos? Worth thinking about.
They should have been able to grab stored codes on day 1 and diagnose.

Not sure what you mean by contact block. I ordered and installed the part pictured here: https://www.fcpeuro.com/products/volvo- ... ly-8626325

The shop that was working on it is a local chain that mainly does tires and brakes, but does have trustworthy mechanics. My dad is good friends with the manager as well, so they wouldn't screw me over, but they don't specializing in Volvos or anything.

For anyone else still following, I unplugged both the fuel pump relay (in case that was shorting or something, idk) and the main system relay (big blue square relay 1 from the fuse box), but fuse #8 is still blowing the second I plug one in, even with no key in the car. So I think there's a short somewhere causing way more than 15 amps to run through that fuse (but not enough to blow one of the bigger 60 amp fuses that I think is also along the same circuit). Going to try and use a multimeter tomorrow to measure the volts/amps going through and see if that points me in any directions. I don't understand electricity at all, but I'm confused what could be causing a battery measured at 12V and 5A to be frying a 15A fuse without even the key in the ignition.

[abscate]

My tailgate wires shorted on my V70 and took out my immobilizer circuit when I hit the lock button, by blowing that same fuse.

You have found cause for no start, next step is to find root cause for the fuse, which will be a short.

Be careful with the ammeter , it can't take more than a few hundred milliamperes before blowing. You do not want it in series with the battery at all, measuring current.

What else is in fuse 8 on your car in the owners manual? Let's check that stuff first.

Your battery can put out 100s of Amps if the load is small. A short circuit is the smallest load possible.

That fuse 8 is not live until you turn the key on, at which it shorts downstream, pulls >15 Amps and pops the fuse

[abscate]

Here's how you confirm the short.

Key off
Pull fuse 8
Key on
Voltmeter on 12 volts scale
Measure voltage on fuse pin ( fuse removed) to a ground...bare metal spot on car. One side will be battery voltage, one will be near zero

The one near zero is the electrical load.
Voltmeter on ohm scale
Now measure resistance of the zero side or electrical load to the same ground point. If it's near zero, you have a short. It should measure something 2 Ohm , if the circuit is rated at 15 amps

[Cricket502]

What else is in fuse 8 on your car in the owners manual? Let's check that stuff first.

The fuse box says the light switch is also on that fuse. With the fuse burned out, my parking lights don't turn on but the headlights do, so only part of the light switch is non-functional with the fuse burned. Again, it burns as soon as I insert the fuse or connect the battery, even if the key is off. So I need to try and see if any wiring seems amiss in that area. I'll try measuring volts and ohms like you said to confirm the short.

My rheostat (dimmer wheel) has always been loose in the dash and could pull out if I want it to, so I'll check and make sure that is still working and doesn't have any wiring issues. The wiring diagram shows that rheostat going through the dash cable harness, and one of the wires goes to the light switch. So maybe if they're both non-functional that'll tell me something. There are a whole lot of wires under the dash to try and find a single one that's shorted

[abscate]

On my 99 V70T5M fuse 8 goes right to the ignition switch, terminal 30. Are you sure the S70 is different? That fits the partial light behavior too.

Oh, my bad. I was looking at the A fuse box and you are probably on the C box

[Cricket502]

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On my 99 V70T5M fuse 8 goes right to the ignition switch, terminal 30. Are you sure the S70 is different? That fits the partial light behavior too.

Oh, my bad. I was looking at the A fuse box and you are probably on the C box

Yeah sorry, I'm looking at 11C/8 which is 15 amps

[Cricket502]

Fixed it! Thanks very much to abscate for the instructions with the multimeter. My dad had the beep setting turned on while we held one prong on the shorted side of the fuse with the other side to ground while I poked around under the dash until the beep disappeared. Ultimately a wire bundle that sits along a metal support down there had rubbed through the tape and insulation, and when it was resting on the support there was bare metal making contact. Some zip ties and electrical tape saved the day!

Wire bundle rubbed down through the insulation

20170723_134907.jpg (1.58 MiB) Viewed 1071 times

[Cricket502]

Fixed it! Thanks very much to abscate for the instructions with the multimeter, and everyone else for the suggestions. My dad had the beep setting turned on while we held one prong on the shorted side of the fuse with the other side to ground while I poked around under the dash until the beep disappeared. Ultimately a wire bundle that sits along a metal support down there had rubbed through the tape and insulation, and when it was resting on the support there was bare metal making contact. Some zip ties and electrical tape saved the day!

[abscate]

Insert Viking horns here !!

[BEJinFbk]

Looking at the '98 fuses, #8 feeds the alarm, instrument cluster and lights.
I'd start with the easy one and unplug the light switch, then try another fuse.
Then the alarm module. If your still blowing fuses, this could get fun...