1996 850 ECC dead...bad connection at fuse box #31

[JimBee]

You mentioned you've been reading schematics. Do you have the one that includes all circuitry from the battery, through the fuse box and relay to the ECC and on to the power stage, blower motor and grounds? Is there a relay or a circuit breaker on that system? You say you've swapped all the removable electrics, but do you KNOW they all work?

I went through this a year and a half ago. I went to the junk yard with a multimeter and a looooong test wire (10 feet of lamp cord with alligator clips) and gingerly : ) dismantled the electrical system of a junker, tracing wires for continuity with the schematic handy for notes.

Then when I got home, I checked all those wires for continuity, and making sure I had good grounds. The fan would run when I direct grounded it to the chassis point by the alarm control box. The fan is always hot, speed is adjusted on the ground side through the power stage.

After pulling all the connectors apart, juicing them a bit with dialectric grease and reassembling everything at some point it just started to work. I got power in to the ECC from the fuse box (yellow w. violet trace?). I suspected the fat blue wire (ground I think) had something to do with it, maybe one of its connectors. After reconnecting that last time it just worked.

If you're not getting power in to the ECC that should be a fairly easy problem to fix, once you trace the open circuit to its power source from the ECC. If you suspect the key switch, you can power the line voltage in from another source and see if that works. You don't mention using your multimeter. I found my little $5.00 Harbor Freight special to be invaluable on this hunt.

I also have several ECC's and they all worked in my '93, so I knew they should work in the '96. Like I said, eventually one did and I really hadn't changed any components, just unplugged, replugged everything—but I knew I had good circuitry b/c of the tracing with the meter.

On second thought, I think I did pull the cover off the fan motor and cleaned up the back end, got a little white lithium grease in the bearing, though it was running okay on full power before that.

One more afterthought: If you have an open circuit downline from the ECC, you might not be getting the ECC to power. I think the small brown wire ECC to powerstage relay?? might complete that circuit.
I'm not sure though. The schematic will tell you.

I got the schematic from a service tech. I think he printed off Vadis.

The repurpose project is cool. It reminds me of the flashlight I helped my 4 year old grandson make out of an excedrin box. Right after that a storm knocked out the lights and he was the hero of the moment with his little flashlight.

[z31jaime]

check the plugs. I had one of the cables push back out of the plug and my ECC wouldn't power up. I pushed it back in and BAM ECC worked.

[Ben850]

check the plugs. I had one of the cables push back out of the plug and my ECC wouldn't power up. I pushed it back in and BAM ECC worked.

You know, in my haste I haven't paid much attention to the connectors other than plugging and unplugging. I know there were not any obvious wires hanging, but you do bring up a valid point. Sometimes things are simpler than they seem.
I will chime back later. Thanks.

Also, to address the fan, I did have it apart and noticed the brushes seemed to be near their end. Not completely done but possibly at the wear limit and may be beginning to cross contacts on the armature.
I have a Volvo factory Bosch rebuilt kit with brushes and springs on the way. I hope to see that in a day or two. The bearings are fine.
This is the second fan. The previous owner had the fan hard wired to a ground switch and trashed the bearings. I deleted all of the riggings and I did have everything up and running for a couple months. It died without warning.

[esl_97_850_T5]

Ben850,

I love how you mounted the LED and pushbutton so Sure-ly, thereby avoiding having them dangling, competing for space with the 3 leads to plug into the OBDII connector, and avoiding buying one of those Radio Shack mounting boxes to accomplish the same "mounting" purpose. Cool.

esl_97_850_T5

[Ben850]

Ben850,

I love how you mounted the LED and pushbutton so Sure-ly, thereby avoiding having them dangling, competing for space with the 3 leads to plug into the OBDII connector, and avoiding buying one of those Radio Shack mounting boxes to accomplish the same "mounting" purpose. Cool.

esl_97_850_T5

I "Surely" Appreciate the affirmation.

Jim, you have given me a few more options. Thanks.
I love the junk yard, maybe more so than most. I try to not spend the complete day but they sometimes have to kick me out.
I am more than willing to spend the money on the correct part if I know the fault.

[osman]

I built a similar flash-code scanner for my 94 mercedes s420. It allowed me to diagnose every system independently. Very helpful. I like the deodorant box idea as well. I think the radio shack mounting box cost me $5.

[Ben850]

I received my heater motor rebuild kit today and took care of that. Still snowing so I won't get to doing anymore diagnostics until Monday.

Brushes and emery boards. That's it.

The brushes were not too far gone but the springs were well extended and likely were not keeping proper pressure to the armature contacts.

A little blurry, Spring and Brush slider.

Comparison.

The bearings are fine. The new brushes should rule out the fan.

I will swap another power stage as well on Monday. I have three of the part # 9134932 which is appropriate.
With multi-meter and schematics in hand, I will figure this out.

[jreed]

I read somewhere a while back that the new brushes will generate a lot of dust for the first few minutes they are used, as they conform to the shape of the commutator. The brush dust was suspected of building up and causing the AC evaporator to corrode prematurely. I can't find the reference and I don't know if it's true but you might want to run the motor on the test bench for a few minutes before installing it in the car.

[Ben850]

I read somewhere a while back that the new brushes will generate a lot of dust for the first few minutes they are used, as they conform to the shape of the commutator. The brush dust was suspected of building up and causing the AC evaporator to corrode prematurely. I can't find the reference and I don't know if it's true but you might want to run the motor on the test bench for a few minutes before installing it in the car.

I hadn't considered that really. The evaporator on my '93 must be bullet proof because it is 21 years old, spent 19 years without a cabin filter, and survived a clogged PCV system that left the whole car covered with a film of oil inside and out. when I changed out the fan in the '93, I took a forest of pine needles out of the ductwork and wiped oil from the area like sludge.
I charged the system last summer for the first time in who knows how long. It held all summer.

I did plan on bringing my battery charger inside today to break in the new brushes on the bench, as to not tax the power stage too much while they get seated.

[Ben850]

The fan checks out great on the bench. It is quiet and seems to be perfectly balanced.
I ran it on slow charge (trickle) and full charge mode for several minutes.

Indoor bench test.

Custom shock mount. Ventilated.

There was no noticeable dust to speak of.
I took it apart and shot the brushes and armature with contact cleaner, put it back together and ran it some more.

The spring is now fully compressed.

Final cleaning.

I have no worries about this fan being a weak link in the system anymore.

I realize this thread could be divided into several as it covers different subjects but they all apply to the original title of diagnosing, and ruling out what may be the intermittent issue with my ECC.