Blower speed,

[mekelly]

As I understand it, if you have a bad blower motor resistor, you only get high speed.

I have sort of the opposite problem. I have all the fan speeds but high speed isn't always the same. When set on high, it is definitely higher than the next lowest speed(and blowing pretty hard) but occasionally the fan will start blowing ~30-40% harder than it was previously. It seems like that's supposed to be the true highest speed. Usually no big deal but here in Atlanta when it's 95, the 'true' high speed makes a big difference in cooling off the car and keeping it cool (especially for those in the back seat)!

I've seen it happen a couple of times after I've made a turn (probably a coincidence). Other times it will just start blowing much harder.

The only two things I think this could be are the blower motor resistor or the switch itself on the dash. I guess it could also be the blower motor itself.

Anyone ever experience this? Thoughts?

 

[Gadget X]

Could also be an indicator for an alternator or voltage regulator going bad. If the voltage drops a little, then the blower will slow down, and vice-versa.

 

[mekelly]

I didn't think about the alternator. I guess I could have that checked at Advanced or monitor the voltage.

 

[2stroke]

My thought is that you might have a bunch of leaves and junk wrapped in the blower box.

 

[mekelly]

I did clean out a bunch of debris last fall after reading the sticky on the forum. I'll check again when I pull the resistor to take a look at it.

 

[larrydd999]

I rebuilt my A/C recently and when I put the housing back my resistor assembly wouldn't work. I pulled the resistor plug off and cleaned the contacts - adding 'bulb grease' (can't remember the proper name) to the contacts and all was well. You might try that and see if it helps.

 

[Arne13]

If you are running it on max a.c. when this happens, could be the blend door is opening and shutting. When shut, it will make the air blow harder and if it opens, the air will slow down. Something to do with vacuum? This ought to date me, maybe working like the old vacuum wipers. When pulling a big load your vacuum goes down, Wipers used to slow down, maybe when turning a corner and you accelerate hard coming out of the turn, blend door opens. Just guessing, good luck with it, Arne.

 

[mekelly]

Very interesting Arne13, I never thought about vacuum.

I am using it on Max A/C and I commented to my son how sometimes the blower kicks in (to a higher speed) when making a turn. It's only happened a few times like that, but it was more than once.

I'll check vacuum lines for breaks or leaks.

 

[Arne13]

If that happens to be it, let us know. Just out of curiosity. Could be a cracked housing on the vacuum motor, also. Arne.

 

[larrydd999]

Two other possibilities: Perhaps the motor is going away. I haven't taken one apart, but if it's a 4 brush motor and one is not making good contact with the commutator the motor won't run at full speed. (Obviously if it's a two brush motor and one isn't making it won't run at all.) The second is that a motor bearing (bushing) is failing. They're generally 'permanently lubricated' sleeve bearings and eventually will fail.

 

[Roadrunner777]

Could be the blower motor relay, it does weirdness on it's way to failure. Swap it with another one from the relay block, they are all the same.

 

[mekelly]

My EEC relay was flaky when hot and so i just replaced it and the fuel pump relay several weeks ago. They are all original so I guess I could replace blower motor relay as well as well.

 

[kruella]

could be a bad ground to the blower motor take out one screw, clean paint off behind it, run another ground from that point.

 

[rbbaker]

I have a similar issue with mine. I have already replaced the motor since the old one died anyhow. There are many times when I am at a stop light I notice the blower speed being fairly low. I look at my gauge and my voltage is quite low. I shift into neutral and watch the gauge come back up and the fan speed increase. I am leaning towards alternator or battery.

 

[rbbaker]

Truck needed a boost yesterday after I shut it off, fortunately I was close to home so the wife brought her Ex to boost me. Last night I changed both battery terminal clamps. Truck starts with out an issue and the problem I was having with the fan speed going up and down had disappeared and is now working nice and steady. Might be something to look at.

 

[mekelly]

Will do, thanks!

 

[larrydd999]

Just for what it's worth, I recently purchased one of the $6 voltmeters that plug into the lighter socket and run it from time to time (after I checked it against a precision DMM - it reads about 0.4 volts low) on my two Gen1's. When the engine is running the voltage goes from around 13.8 to 14.6 regardless of RPM, electrical load, etc. but the voltmeter in the dash hardly moves at all. The only thing I've found the stock voltmeter useful for is one time when it read zero - the alternator had just failed so I was running on battery only.