Gary Lewis Posted January 16 Share Posted January 16 My father used to say "Ain't that a revolting development." I used to think I understood, but as of this morning I HAVE IT! After the conversation with René yesterday I thought I'd test Big Blue's HVAC blower motor. The plan was to take it out and oil it and then see what difference that made. But it dawned on me that I might want to take some benchmark measurements first to see if I'd made any improvements. However, when I did I was dismayed, or maybe revolted, by the results. Here's what I got as well as some calc's to go with it using the as-is harness in the truck: Test 1: Battery @ 12.5V, positive terminal to motor @ 11.15v, negative terminal @ 3.2v, and current @ 10.2 amps. WOW! Effective voltage to the motor is only 9.3v??? That's only 74%! And 95 watts. Test 2: Battery @ 12.8v, voltage to motor @ 8.4v, and current @ 8.6A for 72 watts Test 3: Battery at 13.7v, voltage to motor @ 8.5v, and current @ 8.6A for 73 watts Note that some of the differences in the readings might be due to having introduced a different meter to read battery voltage, and directly reading voltage to the motor instead of reading the negative side and then the positive side. But nevertheless, there are PROBLEMS! And I thought I had that covered, at least on the negative side, with a relay. But then I wondered what would happen if I jumpered the motor directly to the battery using the light test jumpers I have, which might be 18 gauge. And here are those results: Test A: Battery @ 13.0 volts and presumably that's what the motor saw, but I doubt it given the leads. The current was 14.3 amps, which calculates to 186 watts. Test B: Battery @ 13.5v and current @ 14.5 amps for 196 watts. And I'll tell you, the air flow in the cab was night and day different to what I've been getting! There's nothing wrong with the blower motor that a little bit more juice wouldn't solve. So now I'm going to be checking the wiring. I thought I put a relay in the ground circuit, but if so I must not have wired it correctly. And I certainly need a relay in the power feed. Link to comment Share on other sites More sharing options...
85lebaront2 Posted January 16 Share Posted January 16 Gary, inside the cab, near the HVAC inlet, is a pretty healthy connector, should be brown, if yours isn't partially melted I will be surprised. It carries the blower ground side connections to the switch. Also take a good look at the blower switch plug and the two lead underhood plug for the blower motor. All of these will typically show heat damage. Basically check every plug in the blower circuit for signs of being overheated and clean or replace them. For some reason Ford decided to use the ground side for speed selection (like Chrysler) unlike GM who used the power side and then a big relay with a 30 amp in-line fuse off the alternator for high. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 16 Author Share Posted January 16 Gary, inside the cab, near the HVAC inlet, is a pretty healthy connector, should be brown, if yours isn't partially melted I will be surprised. It carries the blower ground side connections to the switch. Also take a good look at the blower switch plug and the two lead underhood plug for the blower motor. All of these will typically show heat damage. Basically check every plug in the blower circuit for signs of being overheated and clean or replace them. For some reason Ford decided to use the ground side for speed selection (like Chrysler) unlike GM who used the power side and then a big relay with a 30 amp in-line fuse off the alternator for high. Thanks, Bill. But I'm not really wanting to fix the existing wiring since the wires are small and long and the connectors are many - although I did check them when I did the transformation. Instead I want relays to give full power to the motor at all times when the ignition is on, and a relay to give a solid ground when in High. I thought I was there on the ground side because I have Relay #5 in the passenger's side PDB, as shown below. But that isn't working as there's a ground on the O/BK going to the motor if the blower control is in High, even when the key is off. Or even when #5 is pulled out of the PDB. So I have a problem there. And that drawing is wrong since I no longer use Relay #1 to trigger the starter and am using the fender-mounted relay instead. So my plan is to use #1 to provide power to the motor and #5 for the ground in High. That should give me full battery voltage at the motor. As for the connector under the hood, that's where I broke into the system. I've made pins to insert into the female side by cutting 1/4" male terminals down to fit and then I'm jumpering to the male connector. So I know it is clean. So, what do you think of that plan? Link to comment Share on other sites More sharing options...
85lebaront2 Posted January 16 Share Posted January 16 Thanks, Bill. But I'm not really wanting to fix the existing wiring since the wires are small and long and the connectors are many - although I did check them when I did the transformation. Instead I want relays to give full power to the motor at all times when the ignition is on, and a relay to give a solid ground when in High. I thought I was there on the ground side because I have Relay #5 in the passenger's side PDB, as shown below. But that isn't working as there's a ground on the O/BK going to the motor if the blower control is in High, even when the key is off. Or even when #5 is pulled out of the PDB. So I have a problem there. And that drawing is wrong since I no longer use Relay #1 to trigger the starter and am using the fender-mounted relay instead. So my plan is to use #1 to provide power to the motor and #5 for the ground in High. That should give me full battery voltage at the motor. As for the connector under the hood, that's where I broke into the system. I've made pins to insert into the female side by cutting 1/4" male terminals down to fit and then I'm jumpering to the male connector. So I know it is clean. So, what do you think of that plan? Ok, one relay to get direct power to the O blower motor wire (+) and the other to ground the B blower motor wire (becomes O/BK) in high. Since you are re doing all of that wiring, I would look into using terminal 30 on the ground side relay as the ground pin, 87a to ground the switch and 87 to ground the blower motor. That way you can eliminate some of the present connectors. I may at some point mess with the HVAC wiring on Darth, but the 1996 system is so greatly improved it may not be needed. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 16 Author Share Posted January 16 Ok, one relay to get direct power to the O blower motor wire (+) and the other to ground the B blower motor wire (becomes O/BK) in high. Since you are re doing all of that wiring, I would look into using terminal 30 on the ground side relay as the ground pin, 87a to ground the switch and 87 to ground the blower motor. That way you can eliminate some of the present connectors. I may at some point mess with the HVAC wiring on Darth, but the 1996 system is so greatly improved it may not be needed. I'm with you for all of that but the "87a to ground the switch" bit. Can you say that another way? I've simplified the page from the 85 EVTM to remove everything that doesn't apply to Big Blue and am preparing to add the relays. I deleted the text that explains how the HVAC system works, which gives me room to work. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted January 16 Share Posted January 16 Now you understand why I installed the E450 fan relay kit I got from U-haul parts online. It sits inside the passenger fender just clear of the hood hinge and jack. Came with adhesive heat shrink crimps already installed. Edit: it takes power directly from the input bus connection of my little fuse & relay box, through a 30A inline fuse holder to the blower motor. Link to comment Share on other sites More sharing options...
85lebaront2 Posted January 16 Share Posted January 16 I'm with you for all of that but the "87a to ground the switch" bit. Can you say that another way? I've simplified the page from the 85 EVTM to remove everything that doesn't apply to Big Blue and am preparing to add the relays. I deleted the text that explains how the HVAC system works, which gives me room to work. Gary, the idea is to move the ground side of the switch to a solid underhood ground, probably right at the battery. 87a is connected to 30 with the relay de-energised so if the switch ground is through it it will have the same ground as the Hi setting. It would just be 1 more wire from switch to relay box. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 17 Author Share Posted January 17 Gary, the idea is to move the ground side of the switch to a solid underhood ground, probably right at the battery. 87a is connected to 30 with the relay de-energised so if the switch ground is through it it will have the same ground as the Hi setting. It would just be 1 more wire from switch to relay box. Jim - Yes, I understand why. For sure. Luckily I have two relay spots in the PDB so I can use those spots and make the blower HUMMM! Jim - I'm still not 100% sure I understand. From what I'm looking at I only have to break into two wires, as shown below. The top one is to supply power and the bottom one is to supply the ground, but only when the switch goes to High. I'll try to map out what you are saying, but I don't want to run any wires to the switch. From what I'm seeing I just need 30 and 87 on the ground relay and let the current go through the resistors for the lower speeds. But I'm sure I'm missing something. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted January 17 Share Posted January 17 Jim - Yes, I understand why. For sure. Luckily I have two relay spots in the PDB so I can use those spots and make the blower HUMMM! Jim - I'm still not 100% sure I understand. From what I'm looking at I only have to break into two wires, as shown below. The top one is to supply power and the bottom one is to supply the ground, but only when the switch goes to High. I'll try to map out what you are saying, but I don't want to run any wires to the switch. From what I'm seeing I just need 30 and 87 on the ground relay and let the current go through the resistors for the lower speeds. But I'm sure I'm missing something. Your truck was setup as W/Euraspark... correct? Yeah, the orange wire triggers the relay, that I grounded through the mounting screw to the fender. The relay gets power from the Megafuse connection, through an inline fuse holder, and provides power to the blower motor in all positions but 'off'. You don't need to relay the ground side.(but you could) 261 is heavy enough to handle the blower easily. Run a dedicated ground wire to 701, like I did with my audio upgrade, and run an overlay ground past Splices 802 & 165 from the speed selector switch. I find it interesting that G106 is connected all the time to the resistor. Didn't we have a user puzzling why they had one fan speed (low) that never shut off? And no high or intermediate speeds? Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 17 Author Share Posted January 17 Your truck was setup as W/Euraspark... correct? Yeah, the orange wire triggers the relay, that I grounded through the mounting screw to the fender. The relay gets power from the Megafuse connection, through an inline fuse holder, and provides power to the blower motor in all positions but 'off'. You don't need to relay the ground side.(but you could) 261 is heavy enough to handle the blower easily. Run a dedicated ground wire to 701, like I did with my audio upgrade, and run an overlay ground past Splices 802 & 165 from the speed selector switch. I find it interesting that G106 is connected all the time to the resistor. Didn't we have a user puzzling why they had one fan speed (low) that never shut off? And no high or intermediate speeds? Euraspark? I don't recognize that term, but then it is a new year. So please refresh my memory. As for the ground relay, I already have it, although it isn't wired quite right. So I just need to sort that out and I'll have the ground relay that will fix that voltage drop problem - and take a load off the switch itself. I should have posted my cleaned up version of that schematic instead of the very busy one from the '85 EVTM. In any case, your comment about G106 clicked and now I see what Bill is saying - run Ckt 57 to the ground relay and use 87A to ground it. But then you'd lose the ground to the AC clutch when the blower is in high and the relay is picked. (I'm not sure Big Blue is wired that way but will check it out when I'm "in there".) As for someone with only Low and it won't shut off, I've slept since then and don't remember that very clearly. But that would take two problems: The function switch would have to feed power even in the off position, and either the blower would have to be bad or G701 bad. Right? But Rene's high-only problem could be due to a blown thermal limiter or a bad G106. Does that make sense? Link to comment Share on other sites More sharing options...
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