Rear blower power = engine rpm

[Rickysa]

Sorry for yet another post this evening, but I've been working on some odds and ends...cleaned all of the blowers (foot well, rear engine (heat), fresh air) and noticed that the rear blower behaves concurrent with the engine rpm...rev her up, get full blower. Not automatic heat...but set on "3" the blower dies down at idle and speeds up on throttle.

Relay?

[pete3799]

Check your alternator.
Voltage at idle?
voltage at 2000rpm?

[86 911 Targa]

Your headlights are most likely varying in brightness as a function of RPM's.

If so, pete3799 is spot on.

Good luck,

Gerry

[timmy2]

Just a thought...
Almost sounds like the blower motor isn't working. With backdated heat (No blower at all) I get more flow with more RPM's. Pull the duct off and see if the motor is actually working.

[Rickysa]

Just replaced the voltage regulator (due to headlights fluxuating ) and voltages are good...no other electrical issues. That's what led me to think possibly the relay...

(and blower is working)

[wwest]

Originally Posted by Rickysa

Sorry for yet another post this evening, but I've been working on some odds and ends...cleaned all of the blowers (foot well, rear engine (heat), fresh air) and noticed that the rear blower behaves concurrent with the engine rpm...rev her up, get full blower. Not automatic heat...but set on "3" the blower dies down at idle and speeds up on throttle.

Relay?

SOP...possibly..

Haven't looked at the actual internal ducting in my 88 but my 78 had a method for the engine fan forced airflow to bypass the blower motor's squirrel cage blower wheel.

With the engine off turn off the footwell blowers and see if you have forced airflow from the cabin heater blower, if so your cabin heater blower is working.

The 2 fans, the cabin heater blower and the engine cooling fan, are connected in series, or tandem. There are most definitely times that the engine RPM is high enough that the engine fan becomes the primary source for cabin heat airflow.

Sidebar: In certain circumstances , 84-89, the cabin heater blower will be used to help keep the engine cooled.

The cabin heat controller module has 2 extra inputs, one from the speedo, and one from an engine oil temperature sensor. On a HOT day should the oil temperature be above a certain level and the speedo indicate a consistently low speed, say in rush hour stop and go traffic in Austin, the heat controller will turn on the cabin heater blower to "wick" away the heat from the exhaust manifold.

[chrisbruck]

Originally Posted by Rickysa

the rear blower behaves concurrent with the engine rpm...rev her up, get full blower. Not automatic heat...but set on "3" the blower dies down at idle and speeds up on throttle.

Relay?

Mine does something similar. You sure you're not noticing the effect of the engine cooling fan forcing more air in the heating system as the engine revs higher? I can audibly hear more air flowing as a rev the engine higher, which kinda makes sense.

[Rickysa]

Thanks for the feedback...

Last night, cold night here in NC, with a cold engine and before the engine had even really heated up, at idle (heater fan on "3"...full speed, and flappers fully open) I could hear it lightly turning in the rear, and since the footwells are tied to it, they were turning lightly as well...(they act in tandem)

Pulling away from the stop light, the fans would speed up until I shifted into second, and then die back down again...

Not every time, though...sometimes at idle the fans would speed up to full speed for a few seconds.

Before I pulled the heater fan off, it wouldn't even spin when turned on...once I clean/lubed it it spun freely. That's what has me thinking it's electrical. I don't notice anything else electrical acting oddly (as per when I replaced the voltage regulator), which had thoughts going away from the alternator...

Puzzler...

[wwest]

Originally Posted by Rickysa

Thanks for the feedback...

Last night, cold night here in NC, with a cold engine and before the engine had even really heated up, at idle (heater fan on "3"...full speed, and flappers fully open) I could hear it lightly turning in the rear, and since the footwells are tied to it, they were turning lightly as well...(they act in tandem)

Pulling away from the stop light, the fans would speed up until I shifted into second, and then die back down again...

Not every time, though...sometimes at idle the fans would speed up to full speed for a few seconds.

Before I pulled the heater fan off, it wouldn't even spin when turned on...once I clean/lubed it it spun freely. That's what has me thinking it's electrical. I don't notice anything else electrical acting oddly (as per when I replaced the voltage regulator), which had thoughts going away from the alternator...

Puzzler...

The air source for the inlet ducting for the cabin heater blower is downstream, on the pressure side, of the engine cooling blower. So if the cabin heater blower is totally stalled you will still get HEAT provided the levers are pulled up, the higher the engine RPM, the more HEAT.

Speaking of a stalled cabin heater blower....the heat controller uses a reed relay to sense that the cabin heat blower is running, so it will not engage the footwell blower power supply relay unless the cabin heat blower is drawing a specified minimum level of current flow.

I have experienced a situation wherein a low battery would prevent the footwell blowers from working due to the supply voltage being so low the motor wasn't drawing the specified current flow level.

So if the footwell blowers are working then the cabin heater blower back in the engine compartment must be operating. Not sure what the effect might be if the squirrel cage blower wheel is not fully fastened to the motor shaft.

[wwest]

Originally Posted by Rickysa

Thanks for the feedback...

Last night, cold night here in NC, with a cold engine and before the engine had even really heated up, at idle (heater fan on "3"...full speed, and flappers fully open) I could hear it lightly turning in the rear, and since the footwells are tied to it, they were turning lightly as well...(they act in tandem)

The supply voltage for the footwell blower speed control switch is either on or off. If your footwell blowers were varying in speed then the voltage source at the heat control module is to be questioned. And since the cabin heater blower get its voltage from the same point source...

Pulling away from the stop light, the fans would speed up until I shifted into second, and then die back down again...

Not every time, though...sometimes at idle the fans would speed up to full speed for a few seconds.

Before I pulled the heater fan off, it wouldn't even spin when turned on...once I clean/lubed it it spun freely. That's what has me thinking it's electrical. I don't notice anything else electrical acting oddly (as per when I replaced the voltage regulator), which had thoughts going away from the alternator...

Puzzler...

You most likely have a intermittently poor, high ohmage, connection between the battery posts, + or -, and the alternator output or ground.

Most likely at the starter solenoid, but possibly engine to chassis ground point.

Battery keeps the "front" voltage level, but engine compartment voltage is varying with RPM....alternator output level.

Somewhere in the middle....

[wwest]

Results..??

[timmy2]

Check and clen the connectors at the fan and 14 pin connector at the rear fuse panel. See if that makes any difference.