Blower Motor Transister Keeps Failing?
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From: Cadillac, Mi.
Blower Motor Transister Keeps Failing?
2020 Honda Pilot EX-L keeps blowing the climate control blower motor fan transister part h,79330-tz5-a51. Both times climate control set to auto, 70 degrees (so air conditioning cycling to keep at 70). Dealer has not been able to diagnose what the cause is. Has anyone out there experienced this issue and found the cause. No TSB on it. I fear this car is going to be a lemon!
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Junior Member
Joined: Aug 2023
Posts: 3
From: Cadillac, Mi.
The blower motor only blows on high when the transister fails no matter what fan speed is selected? Do you think a new blower motor would fix the problem?. Car is 3 years old with only 9300 miles on it.
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Junior Member
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From: Cadillac, Mi.
New Info
When set on auto the front fan will only blow on high forever and the manual fan speed button will not work to change it. However I just noticed that if I press the rr rear button any adjustments I do are applied to both the rear and front fans. i.e change rear fan speed it also changes front fan speed. So I guess I have a work around - just do not use auto and use rr rear to change rear and front settings. Weird??
Senior Member
Joined: Sep 2018
Posts: 1,466
As far as I know, Honda uses a power transistor to be able to have so many fan settings. Other manufacturers may use resistor packs and have less fan settings.
I am not sure about how Honda has implemented the circuit. And certainly do not know the Honda Pilot. But say, ...
When the bias voltage is applied, the transistor acts as a gate allowing a certain amount of current thru.
Depending upon the transistor used, more voltage then more current. Can be reverse.
If the bias voltage presented is too high (or too low), shorted to power (shorted to ground) then the current flow is only high. Fan then only runs at highest setting.
Understanding this, would check the wiring to the connector of the HVAC blower fan.
Check voltages as the fan speed selector is changed.
I am not sure about how Honda has implemented the circuit. And certainly do not know the Honda Pilot. But say, ...
When the bias voltage is applied, the transistor acts as a gate allowing a certain amount of current thru.
Depending upon the transistor used, more voltage then more current. Can be reverse.
If the bias voltage presented is too high (or too low), shorted to power (shorted to ground) then the current flow is only high. Fan then only runs at highest setting.
Understanding this, would check the wiring to the connector of the HVAC blower fan.
Check voltages as the fan speed selector is changed.
Senior Member
Joined: Sep 2018
Posts: 1,466
When set on auto the front fan will only blow on high forever and the manual fan speed button will not work to change it. However I just noticed that if I press the rr rear button any adjustments I do are applied to both the rear and front fans. i.e change rear fan speed it also changes front fan speed. So I guess I have a work around - just do not use auto and use rr rear to change rear and front settings. Weird??
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masduud
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