has anyone ever thought about using solid state relays instead of normal relays? there is no mechanical parts inside them so nothing can possibly stick plus you could possibly install some sort of PWM to control the speed that the blower motor blows. it would give you more control over the blower motor kind of like on the newer vehicles.

 

Jim I need your help. I understand everything except the diode part. Where do you get them, what do they look like, and how and where is it wired in? A pic would be nice. I got my dash tore apart right now. Thanks

 

I can help. There's a drawing of the diode in the lower left corner of the diagram. When a coil is energized, then suddenly switched off, the collapsing magnetic field can generate a large voltage. In fact this is how the old spark coil and contact arrangement works. The diode is called a snubber, and is meant to shunt this possibly harmful spike of energy. Personally I would use 1n4003 or 1n4004 diodes for this. (higher voltage rating, very little if any additional cost.)

You can get them for about 40 cents at radio shack, or about a penny in quantity on eBay.

You can also buy relays with a snubbing diode or resistor built in.

Here's the picture you asked for.

 

J martin , thank you very much. Very Helpful.

 

Have you guys seem the backs of your switches, mine is burnt.

 

The first sign that I was having a problem was the smoke comming from the bottom of my steering column, all of the current feeding the blower circuit feeds up the steering column, through the tilt assembly, ignition switch, blower switch and then back on out to the blower motor.

I removed the bottom cover and found the wires to the ignition switch, the bottom of the column cover and the switch itself were melted, the switch was starting to hang when It was turned to the start position.

This is when I knew I had to do something to before all of the wiring burned up.

I use PWM controllers on some of my robotic projects and I was thinking about using one to control the blower power and speed, switching and speed are controlled with a 5k-ohm linear pot using 20-gauge wire.

It is 120- amps continuous with a 250-amp surge.

Robot Power

I have the Vyper controller.
Robot Power Products - Vyper

Jim

 

Seems like the design philosophy for this electrical system is:

Use light wires and inadequate switches to protect the fuses.

Like the Vyper controller. Is there one closer to the max rating needed (about 30 amps) that might fit the budget a bit easier?

 

Jim are you talking about something like this?

 

Jim would you happen to know if this new used switch with more spade connectors can be used on my truck? My truck is a 1990 d350. The top switch is what came out of my truck. The bottom switch I got from a dodge van I didn't get the year of it but it looked like an early year.

 

Jim here is one that is rated at 12 to 40 volts at 100 amps 1200 watts

 

"Use light wires and inadequate switches to protect the fuses.
"


Funny!!! I think they were just not made to last more than 10 years... Running maximum currents through wires, but as motors and connections age- the current draw goes up!

 

Sorry, cannot really tell,

looking at the front of the control, is there anything different, a position maybe for a rear blower or evap?

I am sure it could probbly be adapted, the socket would probably have to be replaced anyway.

 

Yes, like that one.

Any Pulse Width Modulation controller with a voltage of 12-36 volts @100-amps should work fine.

Blower motor should not be much of an issue, you cannot really stall the motor like you can in robotics.

I needed the Vyper because I needed overkill, if my drive motor stalls it can exceed 100 amps for an instant in addition, I needed all of the safety like zero start because I am using it around people.

The number of Mosfets are going to determine how much power you can handle,
Looking at the little heat sinks on the circuit board, I would install and duct a small 40mm fan to cool them.

If you are not familiar with a PMW controller, you can start a motor from a crawl to a spin at full torque, the motor is always at 12 volts, the width of the pulse is what determines the speed.

Just make sure your compressor clutch gets a full 12-volts preferably through a relay when it calls for cold.

Jim

 

And then twist them, wrap them all in a bundle and tape them up, so when ONE wire overheats and melts, it now melts all of the wires together in the harness.

I have repaired a lot of cars from the 70's and 80's, the worst were the import cars like Datsun (remember them?) Isuzu's I had found inside the harness where wires were only twisted together, not welded, soldered or a crimp of any kind, just twisted and then all of them taped together.

My design of a wiring harness would use either Teflon of Silicone wire, all circuits ID'd on the jacket and then laced, but hey, no automaker ever ask me .

I only chose the Vyper because of the redundancy and overkill, and it looks cool.

I had used controllers from other robotics companies only to have them fail, once in the full ON state.

They use these controllers on robots like the kind the SWAT team use, like a mini-tank.

There are lots of controllers out there, even ebay has them, shouldn't need more than 50-amps.

I would maybe find a way to mount it in the air stream to keep it cool.

PWM DC Controllers - RobotShop

PWM & Advanced Signal Driven DC Motor Controllers

Jim

 

I just did the conversion using a PWM, so far it's working great. I will update this thread if I have any problems.