Threaded Mode | Linear Mode

Brock · 08-07-2017, **(Subject: Hvac relay? )**

My 08 Prostar has a issue and I can't find the problem. My blower will stay on high..... even if I turn the truck off with no key in it. The only way to get it to stop is to pull the fuse.

When I move the speed control on the hvac controller, it sounds like it's trying to work butbjust stays on high, even if I unplug the hvac controller, the fan keeps blowing on high.

All wiring looks mint from what I can see, this seems to me a simple case of a relay that seized in the closed position but there is no hvac relay in my panel...... there has got to be a relay right? If so where in the f is it?[/align]

Nilao · 08-07-2017, **(Subject: Hvac relay? )**

As far as I know all the guts for the blower is behind the kickpanel in the passenger floor. It's all next to the blower so you have to pull the plastic cover below the fuse box cover. It's not hard once you see how it is done but the first time will be a six pack at least.

Brock · 08-07-2017, **(Subject: Hvac relay? )**

Oh ya, I'm far past that point. I've realized now there is no relay, direct power right to the resistor and the resistor controls the rest. So, off to town to get a new resistor.

Rawze · 08-07-2017, **(Subject: Hvac relay? )**

(08-07-2017 )Brock Wrote: Oh ya, I'm far past that point. I've realized now there is no relay, direct power right to the resistor and the resistor controls the rest. So, off to town to get a new resistor.

Mine in the back bunk went bad. I wired a 30-amp relay up to it and a switch to control the relay that comes on/off with the ignition. I am likely going to make it 2-speed, so I need to limit the current when it is on low...

To limit current, I tested the blower in the bunk with a tail light from my car wired in series instead of the bad controller. It was blowing about 20-25% or so. A truck headlight bulb would likely have the right resistance to make it roughly about 50%. I am thinking of using the headlight bulb ( mounted into the air stream to keep it cool ) instead of a bulky resistor in series with the motor to limit current is the way to go. That way if it goes bad, I can replace it on the cheap and every truck stop would have one.

A am testing all this because my front one is next. It is getting flaky and cutting in-out on the higher settings. I will need to make a simplified 2-speed control for that one for sure.

It s a truck, not a luxury car. I don't need a computer and 10 settings for the blower LOL.

Waterloo · 08-08-2017, **(Subject: Hvac relay? )**

I posted about this a few months ago, the in line resistor for the blower motor. It is a $7 - $14 part that plugs in between the blower motor and the harness in the front HVAC system. Still cannot run the blower on the highest setting, but it is working well on the other settings.

Shandro · 08-08-2017, **(Subject: Hvac relay? )**

a person could also put in a rheostat that should allow full control of the fan speed though it might not work the best at low speeds.

Rawze · 08-08-2017, **(Subject: Hvac relay? )**

(08-08-2017 )Shandro Wrote: a person could also put in a rheostat that should allow full control of the fan speed though it might not work the best at low speeds.

Sounds good but the blower motor is about 15 amps current. Find me a 20-amp rheostat that is not the size of a stack of dinner plates lol. Those things are HUGE!

Shandro · 08-08-2017, **(Subject: Hvac relay? )**

lol being that big it could be tough to find a spot to hide that. only other option I can think of is to make a pwm circuit but that's not quite as simple as a switch with a resistor.

Rawze · 08-08-2017, **(Subject: Hvac relay? )**

(08-08-2017 )Shandro Wrote: lol being that big it could be tough to find a spot to hide that. only other option I can think of is to make a pwm circuit but that's not quite as simple as a switch with a resistor.

Yes, that can be done easy enough, but I wanted to go low-tech on purpose just out of spite lol.