J30t ac/heat issue

[geeman]

AC and heat only work when climate control is on and fan is on high. Any thoughts on what might be the cause?

[Mayhem_J30]

gonna need some more info here. you mean the a/c doesn't work well so it's always on high?...same with heat?

[geeman]

Nope they both work fine but only on high and on climate control (auto), any other setting or manual mode and I get nothing, no air, no heat no fan.Thanks for your help

[Q451990]

So you're saying the fan doesn't come on at lower speeds? There's something called a fan amplifier that can cause this... I think it's a resistor, but I don't remember for sure. Try calling Joe at 1-888-216-5328 (Infinti of Scottsdale) and see if he sells many for the J30 - he should also be able to confirm if that sounds like the problem.

Heath

[geeman]

yes no fan except on high, thanks fo the input I will call joe

[Professor_Mike]

There is a fan control amplifier behind the glovebox. I haven't seen any on the J fail but they do fail on other models. The manual details the check procedure.

[Q45tech]

When the "fan amplifier" [actually a transistor inside a large heat sink] fails the HVAC ecu senses this and engages the Highest speed bypass relay.So this highest speed all the time is a built in indicator that the fan amp module has failed open.

It is an indication that the fan motor is drawing a higher than normal current [all electric motors do this as they age].There is some debate as to the proper repair, obviously the amp module is less expensive than the fan motor but if you repeatededly lose the module replace the fan motor prior to the next module if another failure occurs within a year or two.

Generally a just after summer failure when the cooling input air [to the module heat sink] is not so cool and has stressed the transistor all summer from the fan being one notch below max.Obviously an AC in poor cooling condition will run a higher fan speed than normal after the 10-15 minutes of cool down cycle.

Recirculating the air will draw cooler inside air across the cooling fins of the module thus lowering its temperature and prolonging its life in the event the fan motor is drawing too much current.