Eightdip Posted August 18, 2017 Share Posted August 18, 2017 Hi all! I've tried searching everywhere for a solution but not seen anyone with the same issue as me. I have a 95' SZ Jap import in which the heater/blower will only ever go to the lowest speed. The lights on the dash work and the blower itself does turn off if I press the 'off' button. Also the temperature is only every blazing hot or freezing cold, no in between. All fuses are ok, I've replaced the blower motor relay in the passenger footwell, everything looks ok on the insides of the dials unit and I also replaced the interior temperature sensor (thermister?) in the dashboard yesterday but still no luck. Does anyone have any ideas? Much appreciated! Piers Quote Link to comment Share on other sites More sharing options...
SupraLEDrears Posted August 18, 2017 Share Posted August 18, 2017 Does the Heater control speed dial work? Quote Link to comment Share on other sites More sharing options...
Eightdip Posted August 18, 2017 Author Share Posted August 18, 2017 Does the Heater control speed dial work? The dial itself does work and the green lights work all the way from low to high, but no change to the actual blower speed Quote Link to comment Share on other sites More sharing options...
SupraLEDrears Posted August 19, 2017 Share Posted August 19, 2017 Check if the flap isn't stuck closed. It's the one behind the dash, passenger side. Theres an arm attached to a white flap that moves between hot and cold. Last resort is taking out the lower and uppger gloveboxes to see if the pipes are connected properly. Quote Link to comment Share on other sites More sharing options...
rider Posted August 19, 2017 Share Posted August 19, 2017 http://www.mkivsupra.net/vbb/showthread.php?129221-Interior-blower-fan-only-working-on-slow-speed-ideas Quote Link to comment Share on other sites More sharing options...
Eightdip Posted August 20, 2017 Author Share Posted August 20, 2017 http://www.mkivsupra.net/vbb/showthread.php?129221-Interior-blower-fan-only-working-on-slow-speed-ideas Thanks bud, however there didn't seem to be a solution in there. Quote Link to comment Share on other sites More sharing options...
Eightdip Posted August 20, 2017 Author Share Posted August 20, 2017 Check if the flap isn't stuck closed. It's the one behind the dash, passenger side. Theres an arm attached to a white flap that moves between hot and cold. Last resort is taking out the lower and uppger gloveboxes to see if the pipes are connected properly. I'll have a look asap, I'd assume if any pipes weren't connected properly it wouldn't affect the fan speed? Quote Link to comment Share on other sites More sharing options...
SupraLEDrears Posted August 20, 2017 Share Posted August 20, 2017 I'll have a look asap, I'd assume if any pipes weren't connected properly it wouldn't affect the fan speed? I'm confused now. Are you checking the fan for the speed or how hard it blows out the vents? If one of the pipes are off, all the air would blow into the nearest hole and only a little would reach the vents as there isn't enough pressure to push the air out all the way to the vents. Quote Link to comment Share on other sites More sharing options...
Eightdip Posted August 20, 2017 Author Share Posted August 20, 2017 I'm confused now. Are you checking the fan for the speed or how hard it blows out the vents? If one of the pipes are off, all the air would blow into the nearest hole and only a little would reach the vents as there isn't enough pressure to push the air out all the way to the vents. The blower itself only works at low speed, I would hear if the actual unit was working at higher speeds and not making it to the vents but it isn't. Quote Link to comment Share on other sites More sharing options...
kaahari Posted August 20, 2017 Share Posted August 20, 2017 (edited) Have you tried run hvac unit diagnostics? http://www.jack-frost.co.uk/toyota_supra_air_con.html According service manual (electrical) -The motor is connected to blower motor relay box. -Blower motor relay box gets signal from ac amplifier, what speed is needed. -Ac amplifier gets signal from dash unit if not on "auto" mode If motor itself works the broblem is between 1. Dash unit vs ac amplifier 2. Ac amplifier vs blower motor relay box 3. Blower motor relay box I would start by reading those codes... if nothing, then by measuring, with voltage meter, that blower control box gets current to control signal input wire. Also, trying with other working ac amplifier / dash unit could lead to symptom... Edited August 20, 2017 by kaahari (see edit history) Quote Link to comment Share on other sites More sharing options...
Eightdip Posted August 27, 2017 Author Share Posted August 27, 2017 Guys thank you so much for all the help, I'm super busy at the moment so haven't been able to try any of your diagnostic checks, but I'll hopefully get a chance soon and let you know how it goes! Quote Link to comment Share on other sites More sharing options...
Eightdip Posted November 27, 2019 Author Share Posted November 27, 2019 (edited) Just picking up on this thread, so after trying myself to diagnose and failing miserably, I spent a few hours on it today with an actual capable mechanic and we think it could be the AC amplifier not functioning (part 88650-14270, though maybe different on my J-Spec?). I was super confused with the system as a whole, not realising that the ac amplifier and dash control unit was actually 2 different things (even though it definitely says that above, I just didn't quite get it), the amplifier being presumably hidden somewhere in the depths of the dashboard. I believe the dash control unit has been replaced in the past as it has a part number written on it in tipp-ex (seems like a replacement used part), I've changed the blower motor relay and internal temp sensor, we confirmed today that the blower does indeed work if we send voltage to it so presumably the only option left is the AC amplifier unless anyone else has ideas? Does anyone know of one for sale/where I could get one? I'll try toyota tomorrow but not holding out much hope, will also try Garage D. Edited November 28, 2019 by Eightdip (see edit history) Quote Link to comment Share on other sites More sharing options...
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