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post #1 of (permalink) Old 02-19-2017, 04:42 AM Thread Starter
Randy J
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Join Date: Feb 2017
Posts: 2
Fix your HVAC Blower without cutting the firewall and no heater / HVAC removal DIY

tldr: You can remove the clam and splice the blower wire from the front without the need to remove anything mechanical / Heater / HVAC or cut the square hole in the firewall. diy

With this method, you don't need to worry about removing and adding coolant and burping the system or discharging and recharging the Air Conditioning system and the assorted issues with putting a new dryer in and possibly (probably) introducing leaks with the AC that you may never solve.

My situation and thought process:

Last fall, my wife, Julie, brought the Lotus home from somewhere and said that the blower motor wasn't working. I knew about the issue and how much work it was so I was bummed. This Winter (actually just now), I decided to tackle this project and read everything I could find on the matter. I came across the posts where some had cut the floor in front of the pedals which was a great solution if you didn't want to pull the clam. I floated this by Julie and the response I got was 'You're not cutting a hole in my car!'. I resigned to the fact that I was going to have to do it the hard way which included: removing the clam, removing depleting the coolant, removing the heater core, depleting the refrigerant, removing the dryer, and pulling (with much teeth clenching and curse words) the assembly just to get to the one wire I needed. Then, extend the wire and put it all back together.

We all know that with the 'cut the hole technique', you:

  • Cut a window out of the firewall panel from the cockpit side in front of the pedals (and the perforation holes that are covered up by a plate from Lotus) to get access to the wire going to the blower motor.
  • Crimp on an extension to the orange wire going to the blower and feed it back into the cockpit of the car.
  • Feed the wire through a couple different techniques and eventually up connecting it to the high position of the switch.

With this, you have high speed only (really all you need in my opinion). Benefits of this is that you don't have to pull the clam but you do have to pull at least one seat and then work deep in the footwell while cutting with a death-wheel and then reach another five or so inches further to make the connection.

With no other items that you wanted to replace if you pulled the clam and without a wife that was strongly against cutting holes in the car, this solution works. I didn't have that option so I removed the clam to survey.

What I found, was that there was a thick foam ring between the blower motor and the firewall on the front side of the car. I knew that's where the wire was that I needed so I cut out a 'window' in that foam on the top so that I could see and feel down inside with my hands. There's not much room and I couldn't get my fingers down inside past my second knuckles so my hands were useless. Further, I couldn't see anything at all due to the angles I was looking and lack of light.

It was then that I thought, if I could see down in there and grab the right wire with a pair of long nose pliers, I might be able to pull it off the resistor pack and tease it up high enough to be able to extend it with tools down inside the cavity. Thinking about this (probably too much), I formulated the following plan. It worked out with very little modification.

Here is the camera I bought and used. It worked out fine:


The plan:

Open a window in the foam between the blower motor and the firewall and slightly inboard of the power brake booster. Use a Boroscope (about $30 from Amazon) <link> that plugs into a tablet or phone to find and grab the orange power wire and unplug it from the resistor pack below the blower. Cut the burned end off and butt-splice a new piece of wire on and feed that wire back up out of the window in the foam and out into the area in the front of the car. Seal the hole with new foam and create a new resistor pack using 50w solid state resistors and remote it up near the fuse box by re-purposing the blower motor wiring harness.

Notes with a step by step:

Use the Boroscope camera to survey and evaluate what 'should be' seen.

Major points: (All references are from the cockpit side as if you could see through the firewall)
  • Orange power wire comes out of the motor at 11:00
  • Both orange and black wires loop counter-clockwise and are zip tied at 5:30
  • Orange and black wires exit downward between the plastic body of the blower and the foam at 5:30.

Here is what I saw with the camera. The wires were right where they should have been:


Free orange wire from the resistor pack:
  • Establish the best position of the Boroscope camera to observe the work below.
  • Find the Orange wire as it heads straight down between the fan housing and the foam.
  • Push broad flat tipped screwdriver between foam and wire to break the sticky bond from the wire and create a chase through the foam that the connector can be pulled through. Note: try not to break off any foam as this is an area that can't be easily accessed.
  • Retract the screwdriver out and away.
  • Use long tipped needle nose pliers (perfect were: Harbor Freight 11 inch long needlenose) to grab the orange wire as low as you can.
  • Manipulate the pliers to pull the connector off the resistor pack. (It will pull toward the car's rear, parallel with the bottom of the car) Leverage against the fan housing if needed.

The first look at the connector with the Boroscope camera:

Prep the orange blower motor wire:
  • Using long tipped needle nose pliers or hemostats, pull up on the orange wire to get it into the cavity. Mine came nearly out of the cavity up through the window. I had an option of cutting the little wire tie that held the wire as a strain relief on the spoke at 5:30 to give me a couple more inches. I didn't need to do that in the end.
  • Cut off connector and strip orange wire: Be careful with this part as you don't want to lose parts down in the blower assembly.
  • Hold the end of the wire right at the connector with hemostats and use diagonal cutters to cut the end off.
  • Pull connector end up and out using hemostats.
  • Hold the wire approximately 1 inch back from the end of the wire with hemostats and use strippers to strip the end of the wire. (I ended up using an exacto knife).
  • Try to find the stripped off insulation. If found, remove it with the Abtool, hemostats, or vacuum. (I kept control of the stripped off insulation).

Make connection:
  • Crimp and / or solder butt terminal onto a length of new power wire outside the car.
  • Feed the butt side into the cavity
  • Manipulate the motor wire into the butt connector
  • Crimp butt connector. (I ended up soldering too)
  • Apply heat shrink to the connector. Use a heat gun to shrink it as you don't want to actually burn any foam insulation.

Prep and connection pictures:

Test fan:

Apply 12vdc to the new wire and observe fan operation. I easily found the plug that connected the car wire harness with harness that went down to the blower and it's very accessible. I made a jumper lead for the ground and then put a male spad terminal to put 12vdc to the new wire I just extended and plugged it in. With the key on, the blower turned on when I selected '3' on the switch. If fan doesn't operate, follow a similar process for the negative wire as well as it may be corroded.

Here is the plug you're after:

Here is what the test jumper setup looks like:

Fix incision in the foam insulation:

Glue a patch in place over the existing foam using contact cement on a piece of foam or single sided self stick foam. Seal the area well as this area is under vacuum when the blower is on. You don't want the patch to be sucked into the blower. Aluminized duct tape would be another option.

Hooking it all up:

If you want only one speed, all you need to do is grab the high speed motor wire from the connector and hook it to your new wire. I needed all three speeds so I was able to fabricate a new resistor pack thanks to the guys that posted great instructions here before. The parts cost about $20 from Mouser Electronics.

I was able to use the plug from the existing harness to make my resistors removable if needed and fabricated a plate to mount them on and wired them like below.

Here is the diagram of the new resistor pack:

In order to use this connector, you need to use the ground connector as the blower motor power. So, you need to re-purpose the ground connector for that. I cut the ground wire on both sides of the plug and spliced them together with a small piece of black wire inside of convoluted tubing. There is no connector for blower ground now but hopefully, I won't have to mess with it again. Another plus is that the connector on the switch side doesn't need to be extended, you can use it just like it is after grabbing the black wire and sending that down your new motor wire to the blower.
Here is the wiring diagram of my new resistor pack:

...and a picture of what it looks like finished:

I mounted it under the fuse box using the same screws.

Summary (thanks for making it this far):

I very much appreciate the guys that pioneered the 'cut the hole technique'. It will still be the best option for some and the descriptions and pictures posted in those threads are what allowed me to do what I did.

There is no part of this job that is hard. There are great instructions for removing the clam so don't be scared of that. The area that you're working in is confined but you'll be ok. I saved myself tons of hours and the best part was that I didn't have to deplete the coolant / refrigerant and then chase air conditioning issues afterwards.

BTW, when you're in there, drill the drain holes, install a new tig welded aluminum tank(s) radiator, and upgrade your horns. :-)

Let me know what questions you have and I will be happy to answer.


Last edited by Randy J; 02-20-2017 at 03:04 AM. Reason: typos - improved clarity
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