00 V70 Suddenly No Blower

[C@lvin]

Thanks to warbo in U.K.!!!! Your first post was a winner. And, by the way, welcome to MVS

Fuse 31, 25 amp, was blown. Open circuit indeed

My daughter was driving the car and she nearly always ran the fan full blast. It wasn't making any noises but I imagine that the fan was beginning to need some lubrication. I will lubricate the motors on both cars while I have them out.

[jblackburn]

Sure beats chasing down ground problems, don't it?

Glad you figured it out

[C@lvin]

Sure beats chasing down ground problems, don't it?

Sometimes it is the simplest thing (thank goodness!).

But if I hadn't missed that other fuse I would have lost the opportunity to learn all about all that other stuff

[C@lvin]

Rats! I thought I had this all figured out, BUT........

This is kind of a long post...sorry. Please hang with me

So, remember the original problem was that the blower wouldn't work in the V70 which was because fuse #31 was blown (happened twice).

I have two cars so I have two sets of parts for troubleshooting (a double edged sword as it turns out). Both Blowers, Power Stages, ECC Control Units, and Cabin Temperature Sensors seemed to work fine in several different combinations in both cars when tested. In retrospect, the very brief tests work too brief.

So I oiled both motors with 3-IN-ONE oil and swapped the Power Stage and Blower between the two cars (00 V70 and 98 S70 both with ECC). This is what's happening now - I'll try to give a short version (and it should be clear - I am not an electrician or electronics technician).....

The Blower and Power Stage that started out in the V70 (the problem car) are working fine in the S70. I ran the fan full blast for 25 minutes without a problem.

The Blower and Power Stage that started out in the S70 (working fine up til now) are not working so well in the V70 (the problem car). If the blower gets over about 1/3 speed there is a brief electrical smell and then it stops. After turning the engine off and back on the Blower will work again but always quits anywhere above about 1/3 speed. No fuses are blowing (I assume because the "overload relay" is working correctly - but then why did the fuse blow twice before and isn't doing that any longer). It will run at 1/3 speed or less for long periods of time without incident.

The circuit diagram shows the "overload relay" (2/30) between + source and fuse 31. Then the + flows parallel from the fuse to the Blower (6/28) and the Power Stage (4/31) . One black wire from the Power Stage completes the circuit for the Blower while three wires connect the Power Stage to the ECC controler (4/30). It seems like a simple enought circuit and it also appears as though you only have 4 things that can cause problems; the relay, the Blower, the Power Stage, and the ECC controller.

My problem is that I have all these parts I can swap to do troubleshooting, but now I am afraid that I might destroy a good component by exposing it further to the as yet unknown source of the problem.

I stand ready to receive the collective wisdom of my fellow Volvo enthuisasts.

[Xilikon]

Don't forget the wiring between the parts. A short somewhere would cause this kind of behavior.

EDIT : To elaborate for my answer. If all the parts work fine in the S70 (including the supposed troublesome parts of the V70) then the only thing you can't move over easily is the wiring and that would be where I would concentrate.

[jblackburn]

Yes, I'm still thinking wiring problem as well. Something isn't liking lots of current flowing through it.

[C@lvin]

Thanks for your quick replies.

Any tips on a structured/organized way to try to trace down a short in this circuit? I don't see anything in the manual of electrical diagrams suggesting what the measurements (resistance, voltage, current) should be on any of the wires.

The only thing I haven't swapped is the overload relay. It appears to be doing what it's name suggests is its function, but the fuse did blow twice before. Any idea where that particular relay might be located?

And to reallly exhibit my ignorance, do you think it's possible to put too much oil in the blower motor? Could too much oil behave like water and create a short circuit in the motor itself?

And....if I continued the component swapping strategy do you think I could toast any of the components? Would you feel OK to do that with your own vehicles?

[jblackburn]

I'd go ahead with the swapping things; if you blow up a motor/resistor, they're readily available in junkyards. It's actually very helpful that you have two to switch the things between. I've got one that I pulled 2 years ago when I thought my blower was dying - now that it's been getting colder, it's back to its old flashing light shenanigans, so it may die soon.

If you're smelling a burning smell inside the car, I'd doubt it's the overload relay. Those are located under the black plastic cover of the fusebox that can be removed via 3 Torx screws around the edges.

Don't think the oil is the problem. You can test wires from one source to the next for resistance with one prong of the meter at each end - you should find close to 0 ohms. If you get an astronomically high number, you've found a culprit.

Again, I might double-check all of the ground wires as a starting point. Next, the wires between the blower and resistor and then the blower and back of the ECC.

[C@lvin]

If you're smelling a burning smell inside the car, I'd doubt it's the overload relay.

I'm imagining a scenario where the relay might be allowing too much current before openning up the circuit which might cause one of the other compenents to smell? Though I have never heard of this particular relay failing, others such as the fuel pump relay have been problematic.

Thanks for all your suggestions.

[BEJinFbk]

I don't think it's the relay either.
I'm going with wiring - Namely, the connectors AT the motor
and/or the connector at the power stage that feeds the blower.
If the metal contacts in those connectors appear to have been
overheating, it would fit the symptoms you've described.

I'm guessing that an older motor may have drawn too much
current, overheated the contacts and now you have a recurring
issue that rears it's head after things heat back up. Worth a look.

If that seems like it may be the problem, you might be able to
clean up the contacts, but replacement may also be needed.