How to Install footwell blowers in pre -84 911's

Mysterytrain · 12-19-2006, 09:17 AM

I have posted most of this information in various threads but thought it might be a good idea to group it all together for future reference.
One of the most effective comfort upgrades for pre 1984 cars is to install footwell blowers. While the physical task of mounting the blowers is not difficult the wire routing and control of the blowers can be a challenge. The simplest of all solutions would be to copy what the factory did and use OEM components. My solution became a little bit of both. Like everything else on these cars you will find the list of parts will add up but hopefully your investment of time and money will pay of in making your cold weather driving more comfortable.
Most of my focus will be on the passenger side footwell. It is by far the easiest one to work on and photograph.
I started this project by collecting parts, a right and left blower motor [ one was used, one was new], the duct fittings, ducting, wire, a 3 speed fan switch [ new, OEM type used for the A/C].

In the lower right corner, part 2 is the blower. The piece that attaches to it is a hard yellow duct with two openings. The larger opening connects the flexible ducting thru the dash and into the truck area. The smaller opening feeds the wye connector [18][shown above the blower] that will allow heated air to share the side vents with A/C.
After removing the floor carpet on the passenger side you can remove the one bolt holding the wooden floor board in place and remove that. Carefully, fold back the footwell carpet and you will find an opening with ducting that travels up thru the dash. This is going to be the new home for the blowers.

The next photo shows the trial fit. Note the yellow plastic duct I mentioned above and also the rubber mounting boot at the base of the blower.

This is pretty much the way the factory installed the blowers. It explains why the Carrera's have that huge bulge under the dash. I wanted to keep things looking stock on my 78SC. Those big hairy footwell covers would have covered the map pockets and made the install look like a hack job. I realized that there was alot of real estate behind that opening and figured if I massaged the lip around the opening [..sort of like rolling fender lips] I could position the blowers almost completely inside the cavity and have a very stealth install. This is exactly what I wound up doing. By tapping the lip with a ball peen hammer i was able to fold that recessed edge over. It was a slow process but worked great plus I didn't remove any material.

Moving on to the wiring and control.
With my rear blower removed [after the installation of SSI's] I decided to use the rear blower relay to provide power the footwell blowers. This required running a 12 gauge wire from Pin 87 on the blower relay in the engine compartment fuse panel. My connection was at the 14 pin connector. I then routed the wire thru the tunnel and continued to the passenger footwell where it will soldered to the custom made resistor pack.
The original rear blower circuit looked like this:

I combined the drawing above with the schematic for a Carrera with manual heat.
The new circuit mimicked the factory schematic but eliminated the need for the aux relay for high fan speed. Personally, I felt the fans made to much noise running at full tilt. So my solution was to back all the speeds down a notch. High speed voltage, position 3, was dropped thru a 1 ohm 100 watt resistor, position 2 dropped thru a 2.2 ohm, 100watter and position 1 thru the combined resistance of a 2.2 and 1.0 equaling 3.2.
The new circuit looked like this:

I did some testing with resistors to determine what wattage could be used safely. I felt the smaller 50 watt resistors got way too hot [too hot to touch]. I went with the larger 100 watt power resistors even though I planned to mount them on an aluminum plate for more heat sinking. The larger resistor don't get nearly as hot. They are tucked safely behind the blower in the passenger footwell cavity which remains a cool area. In retrospect, I could have used the 50 watters for the slow and medium speeds and the 100 watt for the high speed but I've been known to over engineer. The next picture shows the resistor pack. If you are counting, don't be confused by the fact that there are 4 resistors mounted to the plate. This picture is actually the resistor pack for my final upgrade. I've included it to show how the resistors where mounted to the plate. The plate is a piece of 1/8" aluminum sheet bent into an 'L' so that I could mount the plate and resistors in side the cavity.

This is the back side showing the three black screws sticking out for mounting.

This next picture shows the resistors mounted in the cavity.

Mysterytrain · 12-19-2006, 09:31 AM

So as you recall the power was routed to the resistor pack from the back of the car. I now needed to build a 4 wire harness that would go from the resistor pack to the 3 speed switch that I planned to locate in the center shifter console. If you look back at the 'new schematic' you can see I used a red [high], orange [med], blue [slow] and white. The white wire attaches to the speed switch wiper and picks up one of the 'dropped' voltages from the resistor pack and re-directs it back to the passenger side footwell blower. Another harness consisting of a white wire and brown wire [ground] was required to feed the blower on the drivers side. I ran this harness from the passenger side cavity up into the trunk and tucked up behind the gauges. I should note that the harnesses where all bundled and wrapped in electrical tape for additional safety and that that OEM look. Snaking the harnesses was the toughest part of all of this.

Next was installing the blower and connecting the ducting. This photo shows the blower installed. The resistor pack is visable behind it. The two blower ground wires crimped together and attached to the cavity sheetmetal.

This is a photo of the wye connector ducting.

And lastly the console 3 speed switch under the voltmeter. The top two knobs are for A/C.

Of course the drivers side install is just like the passenger side except, well tighter.
Purchasing used footwell blowers is a gamble. The used ones I have purchased seem to always need to be lubed now and again to shut them up. They seem to like to squeel a little when first turned on. The upside with the used stuff is that they usually include the yellow plastic duct. The new one I purchased for the drivers side has been trouble free.
Next installment will explain how I couldn't leave well enough alone and went down that slippery slope by adding a 3 speed manual heater console between the seats!

mjshira · 12-19-2006, 09:43 AM

this is great thread. See my previous posts on this. I did this upgrade, well worth the effort!

jbrinkley · 12-19-2006, 11:34 AM

thanks for all the work Ron.

Mysterytrain · 12-19-2006, 03:22 PM

I was very pleased with the upgrade but I never really liked the look of that extra knob in my center console . One day I stumbled upon a NOS center heater console on ebay. The price was right so I figured I would buy it and rid myself of that 'out of place' speed switch. Armed with my new center console I did some trial fitting and made my first unplanned for discovery. Unfortunately, a 78 SC has a handbrake lever assembly with two heater levers mounted on the passenger side of the handbrake. Unfortunate because the heater console interferes with the far right lever's ability to move to its maximum range. I thought of my options. One involved raising the console on standoffs for addition clearance and another was to 'modify' the oval opening on the console to allow for full lever movement. The standoff idea wouldn't work because the console would then interfere with the seats. Hacking or modifying the console was out of the question because this was an NOS part. Ok, so my choice was actually made for me. What I needed to do was buy the parts to convert my handbrake/ heater lever system from the SC style to the carrera sytle. No Problem!
After looking up the prices for the individual parts and being amazed at how much it was going to cost me I found a complete 88 handbrake system with the proper lever arrangement.
78 SC handbrake assembly:

88 handbrake system:

Ok, so now I had all the parts or at least I thought I did. So I began to work on the new electrical connections. Ah, more issues!
The 3 speed console switch is not at all like the A/C fan switch I was using. The factory used 3 lever switches and a cam to make the console switch work. Positions 1 and 2 would be fine because the switch could handle the current draw. But the switch used for position 3 was designed to trigger the aux relay and wasn't up to the task of switching the high current required when running the blowers at high speed. Ok, this meant I needed to install a relay like the factory did.

Factory 3 speed switch:

The grey switches are positions 1 and 2. The small black lever switch is used to trigger the aux relay.

Of course, I didn't like running the fans at B+ [12 to 14 volts] for the high speed so a rework of the factory circuit was required. I also knew about the factory changes in the circuit that eliminated the off position. This factory change made off and position one the same speed. I decided that I would modify that design and make 'Off' a slower speed then Position 1, thus providing me with 4 speeds! Long story short the final circuit looks like this.

The new circuit required 2 additional relays and of course all new harnesses to be fabricated. The relays are mounted at the top of the footwell behind the glove box and next to the cavity opening: not a great picture of them but you get the idea:

Ok, that problem was solved. The next electrical issue was the fact that the heater console switch had a light inside of it. The connections for the lamp are shown in the next picture..the grey/blue and the brown wires.

The brown wires were attached to the chassis under the heater console and the grey/blue wire was connected to the small square heater [ defrost] light to the right of the handbrake.
Ok, so much for the electrical side of this.

RFR · 12-19-2006, 03:27 PM

good post! saved in my archives! just in case

DW SD · 12-19-2006, 03:47 PM

Ron,
Great work!

I'm curious, do you think I could use the footwell blowers alone to suck heat from the heat exchanger, rather than using any of the engine cooling to blow air through the HE?

I haven't run my plumbing from the engine cooling fan to the inlet of the heat exchanger, as yet. I live in San Diego, so only defrost and a mild amount of heat would suffice. Below 50 degrees and I'd be driving another car.

Thank you and great job!

Doug

mjshira · 12-19-2006, 03:52 PM

Quote:

Originally posted by DW SD
Ron,
Great work!

I'm curious, do you think I could use the footwell blowers alone to suck heat from the heat exchanger, rather than using any of the engine cooling to blow air through the HE?

I haven't run my plumbing from the engine cooling fan to the inlet of the heat exchanger, as yet. I live in San Diego, so only defrost and a mild amount of heat would suffice. Below 50 degrees and I'd be driving another car.

Thank you and great job!

Doug

Doug

Don't trust me???

I promise man, it will work!

DW SD · 12-19-2006, 03:56 PM

James,
I trust you, implicitely. Did it work, yet? Not inteding to sow seeds of doubt.

How much air do the footwell blowers pass (unassisted by engine cooling)?

Doug

mjshira · 12-19-2006, 04:06 PM

these things are strong. just running on battery they move a lot of air. it seems to me that two of them should equal the single fresh air blower if not exceed it.

DW SD · 12-19-2006, 04:12 PM

If you are warm enough in Indy, I'll be fine here, I'm sure.
Happy Holidays!

Doug

mjshira · 12-19-2006, 04:13 PM

I really think this will work for you. Especially in socal. Same to you!

Mysterytrain · 12-19-2006, 04:14 PM

Back to the handbrake assembly!

I removed the bolts from the original assembly and then freed the handbrake cables from the yoke. I then had to unwrap the ends of the heater flapper cables from the assembly. This is when I saw my next challenge.
The 78 heater levers look like this:

The 88 levers look like this:

Instead of the cables slipping thru the hole in the levers the new assembly needed the cable loops to slip over shafts mounted on the levers. The pre-formed shape of the SC cables prevented this from happening and attempting to re-shape them caused the ends to break.
Here is a photo of the differences in the cables..it will be on the test:

So, I needed some more parts..two new cables, two new guide and two rubber boots for the ends of the guide tubes.

Some additional notes:
The addition of the center heater console is very nice and looks period correct but the second phase of this project actually took longer then the first.. no doubt because of the new harnesses and my battle with the handbrake assembly.
I made my life easier by removing both seats which is as easy as jacking up the car.
Removal of the old style hand brake assembly is much easier if you disconnect the heater cables from the flappers first.
I was pleasantly surprised to find that the SC has pre-tapped holes for the heater console. I guess that was for the auto heat system. I don't think the manual heat /3 speed console appeared until the footwell blowers were introduced in the 83 turbo.
I'm not sure the second phase of this project was all that cost effective. It might have been easier to buy all the factory stuff and just hook it up. Although, I never liked the idea of the ceramic resistor living in the trunk.
I would have saved myself alot of grief if I had bought an 84 to 86 handbrake assembly.

I had picked up a pair of those hairy footwell blower covers when I first started collecting parts for this project. I ended up stripping the carpet and insulation from them. I used a heat gun to re-shape the plastic panels...basically a trim and fit method. Band saw..some heat, test fit. I then reglued the insulation to the inside surface and screwed the panels over the blowers.
I re-attached the carpet with glue and some velcro strips so that I can still get at the blowers for service. If you look at my car you would never know that there were footwell blowers installed...so I guess it worked out as planned.
You'll be happy to know I'm back on my meds...and JD.