Hello,

With the cold weather we're having here in the Northeast, I'm having a bit of a hassle with the heater in my car. First off, the heat never seems hot enough. I haven't measured the vent temps with a thermometer, but comparing the temperature of the discharge air on my Jaguar is not nearly as hot as my Nissan's heater. Why would this be? With the car fully warmed up, heater on manual max hot, it just isn't adequate for cold days.

Also, another issue seems to be the fan speed which isn't consistent. If I turn the blowers off completely (turning the whole climate control system off) and wait about 10 seconds, then turn the fan switch to Maximum Speed (not defrost), I'll get good, high speed airflow. After about a minute or two, the fan speed will slow down to almost Low. This amount of airflow (even with the air conditioning on) simply isn't enough to keep the windows from fogging, especially if there are two or more people in the car. The airflow is slow even with the car on the highway at high speed. I'm just not sure what is causing this. Both fans appear to be working correctly. I have the same amount of flow from either side of the car.

On an interesting note, if the fans are set for High speed (but have slowed to what seems like Low) and I step on the brakes a few times (enough to make the electric brake pump come on), the fans will jump to high speed until I take my foot off the brake (and the brake pump turns off). Very odd.

Any ideas?

Thanks,
Nick

 

Hi Nick, sounds like my winter last year!! Brrrrr!

Seriously though, the issue with the temperature sounds like a mechanical flap problem - The vacuum operated flaps divert the incoming air over the heater matrix - or not, if they get stuck. Sometimes a good smack will free them up temporarily (so I've heard) - I didn't have this issue myself so I haven't 'been there'.

There might be something in the archives though; I believe it's a fairly common fault.

As far as the fan speed goes, all I can add is that if my car is set to auto and cabin temp sensor detects pre-set temp has been achieved, fans will slow down automatically - you're running it in manual though, right?

A connection between the brakes and the blower speed? that's a new one on me!

There are two relays in each blower, one with a transistorised speed circuit and the other which delivers hi-speed, bypassing the speed control - the relays are fairly exposed to the elements and if your intakes are blocked or wet (in this weather frozen I guess) that could be part of the problem. There's also a drain known as the "duck bill" in the engine compartment near the wiper motor and if that gets plugged up apparently all manner of water and crap can get into the blower housings.

Not much help I'm afraid, hope you get it sorted out soon, pretty cold out there this year.

 

That's your next adventure Nick....the abyss of under the passenger glove box.
Lots of fun adventures waiting for you up under there.

 

I also want to add mine fog up in my 90 VDP. This is due to cold moisture from within the car getting heated up. How the moisture is getting in there is the issue.

Crack your windows a bit while driving, clears it right up for me.
If I get in the car after being out in the rain or snow, my car will fog up within minutes.
And my defroster is blowing mad hot, if this helps at all.

You may have moisture getting in there somehow, doesn't take much. Especially in the winter when it freezes and then thaws out. So you have heat or else there would be no fog.

 

Got to add that mine doesn't fog up except in extreme conditions, maybe once this year when I got into the car soaking wet - I attribute the non-fogging to keeping the climate control on auto with A/C switch lit all the time, even in the coldest weather.

 

Thanks for the replies!

I think fan speed seems to be the biggest issue. With the climate control on Manual mode, temperature full hot, and the fan speed switch on High, the fan speed varies. Shouldn't it stay constant?

I took a video to try to demonstrate this issue. If you listen to the fan noise at about 0:55 (high speed, manual mode, full hot) and then again at 1:18 (high speed, manual mode, full hot -- after turning the system off and waiting about 10 seconds) you can see the fan speeds are not the same, they're blowing much faster after the "reset."

From 0:48 - 0:56, you can hear the fan speed slowly decreasing, all the while set on High Speed. Shouldn't High Speed be High Speed, anytime?


I have noticed the fans are also very sensitive to changes in battery voltage. The fans will slow whenever I touch the brakes (as you can hear at the beginning of the video). They will usually come back up to speed when I release the brakes, but sometimes, the fans will blow faster (and louder) when I make a hard application to the brakes...

Thanks,
Nick