Big Blue's HVAC Blower Issues

[ArdWrknTrk]

Gary,
In this illustration how come there's functions duplicated left and right, but no speed selector connected to the resistor pack?????  🧐

[Gary Lewis]

That's easy.  That is a work-in-progress to show how Big Blue's system works.  

I took the messy page below from the 1985 EVTM and cleaned it up in several ways.  First, I took out the text, which left me room for the to-be power relay that will connect to the BR/O wire between C606A and C603.  Then I erased some of the O/BK wire, giving me room for the to-be ground relay.

Then things got a bit more tricky.  I erased the leftmost set of wiring at C616 and slid the right wiring over since it started life as closest of the two to what BB has.  But then I erased the "vacuum solepot" that he doesn't have as well as the words in the gray for CKT 348 that say it doesn't apply to a 7.5L.

As for the functions being duplicated, the HVAC switch is a 2-pole 7-position unit, with one pole controlling the compressor and the other the fan.

Sorry for the confusion.  I thought I explained that it isn't done, but probably not.  As said, we've been quite busy running errands and making doctor's visits, as we are again today, so I probably don't think through things I post completely.  

[ArdWrknTrk]

I don't have an AC truck so I didn't realize it's a two pole Selector.
Thanks for taking the time to clear that up for me.

[Gary Lewis]

No problem.  I'm just trying to do the best job possible on Big Blue's wiring documentation.  And this area is far from good.

I have a small 3-ring binder in the truck that has owner's manuals, schematics, parts list, etc.  And I'm wanting that to represent everything different.  So as I find something I try to document it.  I've had the passenger-side PDB's schematic in the binder for some time, but when I changed the starter wiring to use the fender-mounted relay instead of the Bosch one I didn't change the schematic.

Now I've redrawn the PDB's schematic to show the ground and power relays for the blower, but want to put this modified EVTM page in the binder as well so need to add those relays to it.  But it looks like all I can do is to put simple relay outlines in it and refer the reader to the PDB drawing that will have the pinouts on the relays called out.  That's because I can't get the little details to be legible in that jpeg.

Basically what I need to do is to page through the '85 EVTM and insert a page in the binder for any deviation from the EVTM.  For instance, there needs to be a page for the headlights since there are relays in the PDB.  And on that page there needs to be a reference to the PDB schematic in the binder.

Thoughts?  Upgrades?  Better ideas?

[Gary Lewis]

Here's what I've created.  First, is the EVTM page revised, followed by the schematic for the passengers side PDB.  These would be the pages I put in Big Blue's binder.  Thoughts?

Oops, I just realized that the latter doesn't show the aux battery and the smart battery isolator.  

[85lebaront2]

Looks pretty good. FYI, if the L, M1 & M2 seem a little slow still, check the ground side for voltage drop. Whoever Ford had designing the wiring for these must have been hired from Ford of Great Britain, only thing missing is this:

[Gary Lewis]

Thanks, Bill.  I agree that they were on something.  

I've gotten quite a few of the changes documented, but have a long way to go.  But I think I'll stick with the ones needed for the blower motor for the time being and then do the others later.

[ArdWrknTrk]

Methinks you'll be re-writing the entire EVTM, and adding an appendix....

Annotations are great, but thinking about a future 'me' having to make sense of a mad scientist previous owners modifications, what would be most helpful is a accurate graphic of the entire PDC with fuses and relays called out at the margin (not unlike the graphic of my fuse panel)

You could even take a picture of it and reduce everything in greyscale, then overlay numbers or letters on that image.
You could even take a page from Ford and use F for fuse, R for relay or B for breaker
F-17 for example.....

Definitely have this on the same physical page.
Nothing is more infuriating than having to look away while you're puzzling your way though a broken (X)

The schematic is "helpful" but it doesn't help me much when I'm under the hood trying to decipher a fault.

[Gary Lewis]

Good idea, Jim, but let me see if I understand.  You are talking about an outline drawing of the PDB that includes the fuses, relays, and diode with callouts telling what each does. Then that would be reduced to sit in a corner of any schematic where that PDB's components appear.  Right?

I have that drawing for the driver's side PDB already, and thought I did for the passenger's side one.  In fact, they were printed, laminated, and stuffed inside the PDB so you could easily see what relay or fuse does which function.  But when I opened the PS PDB the other day it wasn't there.  So I'll need to figure that out.

But I'm not sure about being able to make it legible on the modified EVTM's schematic.  That is a low res jpg and when I put things on it they've come out really poor.  So I'm wondering if I might be better off redrawing the EVTM page in TurboCAD instead of spending time modifying it to match Big Blue.  That would let me print at 600 dpi and that gives good, crisp pictures.

That might actually be easier than cutting & pasting things in Paint.  Looking at the schematic below, all of the fuselinks are now fuses in the PDB, the ammeter is a voltmeter and its wiring includes a relay in the PDB, and the alternator is a 3G.  But I could do it in the EVTM format so it matches other pages.  

[ArdWrknTrk]

No
It would be entirely separate from any schematic.
Just a page by itself with graphic proportional representation of the PDC and a legend at the side/bottom defining each component
Just like my Ford fuse box cover.

[Gary Lewis]

Is this what you have in mind?  It is what is in the EFI/driver's side PDB.  I took a pic of the PDB and drew it up on CAD.  And this is exactly what I need to do on the passenger's side PDB.

[ArdWrknTrk]

What does the inside of an 80-86 fuse box cover look like?

[Gary Lewis]

There's nothing on the inside of the cover, but there is on the outside.  Here's what the cover from Dad's truck looks like:




And here's what the cover on Big Blue looks like, and then there's a sheet in the documentation in the truck that shows which fuse serves what function and its current rating.  But it would be a lot better if I were to put the ratings and usage on the fuse box cover also.

[ArdWrknTrk]

Here's what the cover of my '87 looks like.

[Gary Lewis]

Obviously they hired someone with some reason.  That's a much-improved cover.  

Now for some strange news.  I've been using my DVMs to test voltages to the blower ground relay, the one that was obviously not working properly when I started this quest.

The schematic is below and here are the results of my testing on each pin of the relay:

85: Gets key-on power, as planned

30: It has a great ground

87: Goes to the blower motor as expected.  However it does have ~2 ohms resistance to ground with the relay out, which is what I measure on another resistor pack I have, so this must be correct.

86: This has from 2 to 6 ohms of resistance to ground depending on how you push on the handle of the blower speed switch.  So obviously the switch itself is suspect, although that won't matter with the relay working as it'll be good enough to pull the relay in.  HOWEVER, when I closed the door and the dome lights, all LED, went off the resistance dropped to .9 ohm from 2.2 ohms.  

So I'm  trying to think through what would cause the reading to change that much.  I'm thinking that it is a voltage differential between the ground in the cab, G701, and the ground at the battery, which is where my DVM was connected.  But I cannot detect the difference, and my meters read to .001v.  Having said that, it doesn't take much change in resistance testing to make a big difference.

Maybe that's a red herring and I should stick to the ground relay issue.  

[Gary Lewis]

More testing shows that with the blower ground relay working properly I have another conundrum - I'm getting different voltage drops across different relays when the blower is on high:

Motorcraft: Tried two different ones and I get .31 to .35 volt

Hella: Have one of these and I tested it several times - and got .70 to .73v

Tyco: Have several of these and got .37 - .38 volt drop consistently

?: I have two relays with no names on them, and I got .40 - .42 volt drop across them

Looks like I'll use Motorcraft relays.  

Next up is the blower power relay.  But that may not be for a couple of days.  Lots of church activities, as well as the Chief's game, tomorrow.  Maybe Monday, although I have a Medicare "wellness" checkup that morning.  But the forecast says we are going to have moisture and the temp will be right at 32, so the prognostications vary regarding the solidity of the moisture when it comes down.

[85lebaront2]

How many different relays would you like for testing?

[Gary Lewis]

I think I'm done testing.  Wish I could get that HD Bosch relay in but the bigger terminal won't go.  However, I could cut that terminal down.  

[ArdWrknTrk]

Have a look at the massive relay selection from Texas Industrial Electric

https://www.texasindustrialelectric.com/relays.asp

[Gary Lewis]

Thanks, Jim.  I'm blown away with the number of listings they have.  

I found the ones shown at the bottom of the post and got excited as they are supposedly 50A versions and don't appear to have the larger terminal typical of those relays.  But then I Googled "0 332 019 103" and found this listing on Amazon which says it is a 30A relay.  However, we know that Amazon frequently has incorrect descriptions, so I found this Bosch relay catalog and, sure enough, that is a 30A relay - with a mounting tab no less.

However, the Bosch catalog shows a 0 332 019 109 and says it is a 50A relay.  But Pelican Parts carries that relay and their picture clearly shows the part number and that it is rated at 30A.  What am I missing?