Ok I have searched, I even had a post from years ago I found , still have not got around to it.
but its getting hot out
and would love to solve my blower fan speed issue.

it seems that the logicon works the speed does change as you move it from left to right

but it just seems weak like it’s still at 50 percent of what it could be

the air does seem cold just not moving enough flow to keep the cabin fully chilled on hot day

normally I like to drive the car when it’s not hot like in morning or evening cause I enjoy windows down sunroof open
This is a 90 turbo model with Haltech elite
Haltech turns on ac and that part functions correctly
Maybe the resistor?
any thoughts?

 

Your blower motor resistor is most likely the issue. The logicon (where your temp and fan slider exist) is typically pretty reliable.

 

Ok I found some online
ill order one and try it out

is it located by the blower motor?
easy to access ?

 

There are a couple things to check. It wouldn't hurt to go through and freshen up the logicon while you're at it. Sometimes there are cold solder joints connecting the fan amplifier to the logicon board. Those have been known to cause issues. The amplifier itself may need inspected and components replaced. Dirty slider switches can cause issues too. If you are only getting fan power when the slider is all the way to the right, it is almost certainly the fan voltage regulator/transistor. The logicon controls fan speed with this voltage regulator when the slider is in the middle. When the slider is all the way to the right, it sends full voltage straight to the brushes. Wouldn't hurt to go through everything, but I'd start at the voltage regulator. It is attached to the blower motor assembly, underneath a big aluminum heatsink. I made a post years ago about it. When installing a new one, be sure to apply some thermal paste to the heatsink and regulator. It gets pretty toasty otherwise

 

Ok I will look into it
my logicon seems to work fan speed increases as I move it to the right
i did order the resistor should be here sometime during the week

maybe I need to read some threads on cold soldering the logicon

thank you for the reply

 

there is also a relay for high speed, so when you slide the thing all the way over you should hear a click when it turns on

 

If you do have a gradient for fan speed, your transistor is fine. I would check inside your logicon for cold solder joints, as well as the fan amp box. You could try using some DeoxIT or isopropyl alcohol to clean the slider switches. If those are crusty, they will have increased resistance and will lower your output. I went through and replaced the stuff in my amp a few years ago. Pretty much everything electronic component was still available.

 

Where is the fan amp box?
Thanks for the help guys , I will listen to see if the relay clicks when I turn fan all the way up

 

The amp box is the small box attached to the logicon unit. It kinda nests inside the corner of the assembly. You'll see it when you pull out the logicon. It doesn't completely detach, or at least mine didn't, because the wires coming out weren't actually put to a connector but factory soldered to the main logicon unit.

 

 

Ok finally had time to start looking into things
took the glove box compartment out looking for the resistor? I can’t find anything that looks like the part I ordered, I checked the relay definitely clicks when I turn speed to high. My ac logic on is actually in the glove box there are gauges in it’s original place.

if anyone has any idea where this thing is please let me know
thanks
john

 

the white ceramic ting in the last pic is the resistor. i found that every bit of foam was rotted in the car i bought, which meant half of the air was leaking out of cracks before it even got to the vents.

 

I am having this issue myself now, I need to remove the dash, remove the center HVAC box and replace all the foam so they seal properly, when I turn on the vents, half the air is still being directed at my feet because of the leaks

 

it is a pain in the rear. to do it properly requires removal of the entire dash. also draining the heater core. which becomes another issue as on mine, the bypass valve was leaking and it's a proprietary bit of metal piping. i had to carefully disassemble the blend box/doors and they will break very easily. i recommend sourcing a replacement online, rebuilding it, and swapping. i found the spare i used on yahoo japan, but anywhere will do. good luck!

 

I have a solution for the foam on the clamps that keeps crumbling apart. Scrape the foam off and cut a length of leather, belt or strip or whatever, to length. Glue that onto the clamp in place of the foam. I think it does a pretty good job sealing up the ducts.

 

Hi,
I think my last mechanic fried the transistor trying to find why my ac clutch was not engaging!

Can someone walk me through testing a used replacement transistor before I install it?




You need to pity me, first time using a multimeter I blew out the fuse!

I got hit by lightning, me and electricity have an understanding, do not mess with it!

 

I'll help you out. Gimme a couple days. Work is crazy right now.

 

Thanks, I will get out my unused Multi-meter and start reading the manual!

When all else fails follow the damn instructions.

 

My schedule clears up after Sunday. I'll pull my fan assembly then so I can get some better pictures of this assembly. I might even pull the logicon for some better pictures and just redo the whole guide. That was one of my first ones many years ago.

As far as other stuff to get together to replace the transistor (regulator), make sure you get a nice philips screwdriver so those screws on the heatsink don't strip. I forget whether I used one of those handheld impact tools or not to crack them loose. You may also need a soldering iron and some solder. Optionally, I also used some PC thermal paste for re-installing the regulator and bonding it to the heatsink. Not necessary but it helps a lot with getting heat away from the regulator.

Before tearing into the regulator part of the system, have you probed the plug that connects to that assembly? This would be the feed directly from the logicon amp or relay. I'll try to hook the oscilloscope up to that and take some pictures of that testing as well.

 

Alright GSmith,

heres how we get started. I need you to plug your blower motor back in. We're going to check whats blown first. It's gonna be really easy. Connect up the blower, except leave the voltage regulator/transistor unplugged like in the picture here.



With your multimeter in DC voltage mode, check the pinout of the voltage regulator wires. You will need to turn your car to the Run position to do this, engine doesn't have to be running. With the car in Run, start the fan slider on the logicon all the way left. You should see zero voltage from the signal pin to the fan pin, as well as the red 12v pin from the first relay to the fan pin. There shouldn't be any voltage when the slider is all the way left. Next, move the slider to the first position from the left. This will turn on the blower circuits. When you move the slider to this position, you should hear a click from the first relay. This relay enables 12v from the battery to the voltage regulator and full-power relay. Relay 1 stays on all the way through the range of the slider, providing a constant 12v from the battery to the regulator and fp relay. Check at the connector that there is 12v from the red 12v line to the blue fan line. If there is no voltage, check for 12v at the first relay and diagnose there. If there is 12v, then we can test the signal from the fan amp in the logicon. Measure the voltage from the logicon signal wire to the blue fan line. You should see no voltage when the slider is all the way left (off), then as you step through the range, you should see an increasing voltage between around 5v in the lower range to 9v or 10v in the upper range, and then no voltage on the max position. If you do not see this voltage range, your problem is the amplifier in the logicon. When you push the slider all the way to the right, the logicon stops sending signal from the amp to the voltage regulator, and turns on the full-power relay which feeds a full 12v from the first relay to the fan. If you are checking voltage at the 12v and fan lines where the voltage regulator is unplugged, you will see voltage go to zero when the fan starts running in the max position becuase all that voltage is getting converted into amperage.

Heres a quick rundown of what needs looked at when measuring this connector:
If no 12v voltage (red to blue) with the blower slider on, check the first relay.
If no 5v to 9v signal voltage from amp logicon with slider in middle range, check logicon.
If no fan when slider is all the way on, check full-power relay (full power fan runs independent of regulator).
If all those are good, let me know and I'll dig into that assembly and get out the regulator and we can get that fixed up.

 

Thank you for the instructions, they will be perfect for when I start to fix this important circuit.

Can't drive the car with the windshield all fogged up!

At the present time I do not have a battery to install, putting the drivetrain in comes first.

Please continue with testing the transistor to determine if it is working or not.

When the time comes, I need to determine what is causing the 7.5A B/Y fuse to blow. It does connect into the "Heater & Air Conditioner" circuit, along with seven other circuits.
Again, I am hoping that my NOS compressor will fix this issue.

Thanks again for everything you have done!

 

I've got pictures of testing the regulator assembly, but my computer is pretty much useless to me and I need a few more parts for a new one. I'll put a guide together after the rebuild

 

You and me both, I have to stick a pencil between the keyboard and the screen for it to work now!

I will be looking forward to your guide. Is there a quick bench test for the transistor to see if it is functional?