Blower fan not working when hot outside?

[cujo]

This is a 1999 Malibu.

This is my wife's car so I'm rather baffled as to why this behavior is occurring. It seems that once it gets hot outside, say over 90 degrees or so, and the car is sitting in the Texas sun the blower motor won't kick in. This occurs whether it's the air conditioning or the heater is switched on.

The blower motor seems to work fine in the mornings and late evenings but not at any other time. There are no scary or anomalous noises when the blower is running nor does the blower suddenly kick off while the car is running. I've checked all the fuses and even replaced them with no luck. She's had the blower motor replaced about two years ago for some reason but the blower motor does work when it's (relatively) cooler out.

The A/C unit is blowing cool air even when the blower motor not running. I can verify this because when the car is moving above 25mph the cold air does exit the vents. (could it be a vacuum problem and the vents aren't opening?)

I'm not sure what other information would be helpful at this point but feel free to throw out any questions if I'm not clear.

[corbett_auto]

hmmm, interesting problem. My first thought is that the temperature sensor is bad. Not the one for the engine but the one that measures outside temp. Does the car have an automatic climate control? Does it show you the outside temperature? Pay attention to what it reads, if it is giving a far off reading that is the problem.

My 98 Gran Prix did something very similar to this a few years ago. The sensor is not very expensive and is easy to change. My was located on the radiator support.

[cujo]

Originally Posted by corbett_auto

hmmm, interesting problem. My first thought is that the temperature sensor is bad. Not the one for the engine but the one that measures outside temp. Does the car have an automatic climate control? Does it show you the outside temperature? Pay attention to what it reads, if it is giving a far off reading that is the problem.

My 98 Gran Prix did something very similar to this a few years ago. The sensor is not very expensive and is easy to change. My was located on the radiator support.

No automatic climate control. I'm starting to think the switch in the dashboard/console that regulates the speed of the blower is the culprit. I'm trying to figure out how to get that apart easily to see if that's what's doing it and possibly running a jumper wire to see if that's what is the problem.

Since it's complaining whether I use the A/C or the heater and it's working sporadically, I'm assuming a worn or loose connection.

[cujo]

Originally Posted by cujo

No automatic climate control. I'm starting to think the switch in the dashboard/console that regulates the speed of the blower is the culprit. I'm trying to figure out how to get that apart easily to see if that's what's doing it and possibly running a jumper wire to see if that's what is the problem.

Since it's complaining whether I use the A/C or the heater and it's working sporadically, I'm assuming a worn or loose connection.

There's a part that hooks up to the blower motor called the "resistor pack". I'm going to look and see where this part can be obtained and how it's installed.

(you never know)

[corbett_auto]

I doubt it is the resister pack if it does not work in any speed when it decides not to work. In most cars it by-passes the resisters when on high as it goes through a relay. If it stops working in all speeds follow the power as it travels from the fuse box to the switch. If the power is good then it could be the switch.