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Current going to Blower Motor can be higher than Headlights - why no relay mod?

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Gary Lewis

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

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Jim - The colors are clear in your posts, starting here. And I'm going to do that mod. I just ordered the kit from Utech. However I'll pick up power to the relay & blower from a fuse in the PDB.

Unfortunately I didn't measure the voltage drop to ground before installing the ground relay. But I already know the drop to the motor on the high side is 2.0 volts at 12.8 battery voltage. My understanding is that dc motors have linear current draw with respect to voltage, so at 14.4 volts I'm guessing the voltage drop will be 2.3 volts. The relay should cut that to essentially nothing - at all speeds. And it'll take that much load off the cab circuits.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Gary Lewis

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

Jim - I just perused the TSB index (Documentation/TSB's/TSB Index) and didn't see anything with regard to a blower motor relay. Do you know when that kit was issued? Does it have a part or ID#?

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

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Same as your eBay picture....

But it does have a Ford tag on the socket/harness.
Ill take a look later.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

kramttocs

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

This post was updated on .

In reply to this post by Gary Lewis

Gary - does yours not completely negate the resistor though?

A 5 pin relay is the only way I can think to do this allowing the non-high speeds to be on the NC contact.

Edit: I just reread the early posts in this thread and see that Bill outlined that in the post where the diode was mentioned.

Edit 2: Diagram-

Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio

ArdWrknTrk

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

I don't see a diode..... ----[>|---

Maybe that's what was causing my troubles at first.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

kramttocs

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

Yeah, I am still unsure on if the diode is needed and where it would go so it's not in there

. In just the high switch wire? Both switch wires? Motor side ground wire?

Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio

Gary Lewis

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

In reply to this post by kramttocs

I don't have a diode in the blower motor circuit. I used the diode that is in the PDB on the starter circuit.

Yes, my existing relay negates the resistor, but it only comes in when you switch to High.

My thinking on the power side is to put it on the left side of your drawing, and that is probably what you mean by a "hot" relay. It would provide all the power to the motor, regardless of speed setting. That will probably increase the speed in all settings by some percentage, and I'd expect that to get essentially all of the 16% in High. But as the resistors come in and the current decreases there'd be less voltage drop with the factory approach so less and less increase in speed as you go down on the switch settings.

Gary, AKA "Gary fellow": Profile

Rusty_S85

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

In reply to this post by CountryBumkin

Interesting idea to splice a relay in for the blower motor. I know I will be splicing a relay in on my A/C clutch circuit how ever for my fuel injection to have A/C cutout when I go full throttle. But for the blower itself I never thought of going with a relay for both blower motors.

Never had a connector burn up on mine, the heater blower under the hood I do need to replace the terminal but thats only cause the locking clip broke and I have a zip tie holding it plugged in currently. Real pain when I take the blower motor out to oil the shaft as my blower tends to rust up. Been thinking about trying to source a NOS blower motor just cause of that.

"Old Blue" - '56 Fairlane Town Sedan - 292-4V, Ford-O-Matic transmission, 3.22:1
'63 Belair 2dr sdn - 283-4V, Powerglide transmission, 4.56:1
'78 Cougar XR7 - 351-2V, FMX transmission, 2.75:1 9inch
"Bruno" - '82 F150 Flareside - 302-2V, C6 transmission, 2.75:1 9inch, 31x10.50-15 BFG KO2

ArdWrknTrk

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

In reply to this post by kramttocs

If you look at my pictures you'll see that -at first- I had put the relay in the O/BK wire.
Using it to take the motor to ground with the relay closed -and- letting current flow through the resistor block with the relay open.

But I needed a rethink on that, so went and disassembled the upstream splice, put a butt connector where I had tapped it originally.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

My guess is that the high-side relay is probably twice as effective as the low-side relay. The high-side has pretty large wiring going into the cab from the starter relay to the ignition switch, then still large wire to the fuse box, and then smaller wire to the function switch and then to the motor. So while it goes twice as far as the low-side wiring it has lots of connections in it, and surely the connections have voltage drops in them.

Having measured the high-side voltage drop it now seems like I should measure the low-side drop. And I think I can do that by pulling the relay and jumpering 86 to 87. That will use the factory wiring, and I can measure from the motor's connector to the negative terminal of the battery for the voltage drop.

Headed to the shop......

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

Well, it looks like my guess was WRONG! There's .6 volt drop on the ground side with battery at 12.1 volts and the blower on High. So I fixed the smallest of the problems.

But, for some reason I haven't yet figured out I'm not getting the relay to come in to bring the blower to High. When I jumper 86 to 87 it does speed up the blower. So I have some diagnostics to do. Probably when I put the high-side relay in.

Gary, AKA "Gary fellow": Profile

Rusty_S85

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

When you are jumpering 86 to 87 are you still leaving the rest of the relay hooked up? if so the speed up is to be expected as you are adding double circuits to terminal 87. You have the power from the trigger side supplementing the battery side at terminal 87.

I bet if you take and jumper another wire to the battery terminal on the relay I bet you will see the same increase without jumpering 86 to 87.

Gary Lewis

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

I pulled the relay and made a short jumper with 1/4" male spades on each end. Plugged that into 86 & 86 and then measured the voltage drop from the motor's negative terminal to the battery's ground terminal.

Gary, AKA "Gary fellow": Profile

kramttocs

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

In reply to this post by Gary Lewis

Yes, the relay on the + side is what I did earlier in this thread and made the videos of. That relay is simple to wire up as it just requires cutting and placing the relay in the Br/O or O wires depending if you do it before or after the blower motor connector. I didn't add it to the diagram but we should make a completed diagram with both relays when the dust settles.

Where did you cut in for your ground relay Gary? It can't be done right at the motor or else it would bypass the resistor so curious how you have it so that it only comes on when the switch is on High if not using the NC and NO relay contacts as I drew above.

Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio

kramttocs

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

In reply to this post by ArdWrknTrk

Ok, so you undid the splice. That works.
Really it all comes down to isolating the High circuit from the Lo/M1/M2/resistor circuit so they can be active on their own.
I should have done that in the drawing I posted since it is likely the way most will do it. I am always in the mindset of easily reverting to stock so I was deadheading one of the wires coming out of the splice and then running a new wire for the output of the resistor.
Ultimately the exact same though.

Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio

Gary Lewis

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

In reply to this post by kramttocs

Scott - This is at a high level how I think I did it on the ground relay, and how I want to do it on the power relay. The only thing the ground relay changes is High, but the power relay powers everything.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

Gary, you need to show source and sink in your relays.

So, I have one of the six in my tiny pdc powering the motor at all speeds and the (really nice) U-techcenter blower running the motor back to the 6Ga. ground shared with the power distribution center.

I don't have a way to compare but my windshield seems to clear quicker.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

kramttocs

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

In reply to this post by Gary Lewis

Thanks! So you did it before the splice - that clears it up.

That is how I did the power relay and I think about the only way one would really want to.

But on the ground relay, people will have at least 3 locations for where they can tie in the relay depending on their preference and accessibility

Am I understanding your results though that the ground relay doesn't really add much to help the voltage drop?

Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio

ArdWrknTrk

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

In reply to this post by Gary Lewis

Function to power relay pull-in coil... to ground, hot from battery.

Ground relay: hot coil to ground through the speed switch, motor to battery ground (or some substantial ground near the motor.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Current going to Blower Motor can be higher than Headlights - why no relay mod?

Administrator

ArdWrknTrk wrote

Function to power relay pull-in coil... to ground, hot from battery.

Ground relay: hot coil to ground through the speed switch, motor to battery ground (or some substantial ground near the motor.

Yep, that's how I think I did the ground relay, and how I plan to do the power relay - with the exception that power will be from a fuse in the PDB and then from the battery.

As for providing source, sink, etc, we'll get official schematics when we conclude. But I was just answering Scott's question of where I put the ground relay and thought I might as well show where I want to put the power relay.

Gary, AKA "Gary fellow": Profile

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