PorKen

I'm finally hooking up the blower fan for my NOS Euro-heat-only-head I got from the eBay (the electrical connector is slightly different) so I can have some defog:



In going over the '81 wiring diagram I realized how to bypass the 'Magic Blower' circuit (red area):



The fix is as simple as removing a connector from the resistor unit plug (#8):


The connector is under the hood, just left of the wiper motor.

Fan works as normal otherwise (0 - 4 and the defroster high).

Previously the high speed fan would come on anytime the outside temp was over 70f!
~thread~start~

PorKen

Also, if you want to make '0' on the fan speed dial be really off, instead of just really low, move connector #4 up to #3 (which is blank):



Both of these modifications look like they work up to '88 (928 618 101 01).



On '89 and up (928 616 101 00) the resistor pack thermal switch turns OFF the fan and the connector is wired slightly differently.

I read that the '89 and up resistor pack can be retrofitted to the earlier cars (it's about $40 cheaper too!).

jayc67

So if you make "0" truly off for the fan, does the AC compressor still run in cars with air conditioning? Does that cause the AC to freeze over, running the compressor with no fan?
It always struck me as odd that "0" would not = off for the fan control.
I would like to make this mod, but don't want to risk freezing up the AC system.

Thoughts?

Jay

dr bob

There are two protections from this problem.

Primary is the anti-freeze switch that's in series with the compressor clutch circuit. When evaporator temps drop to near freezing, the clutch is disengaged and the compressor stops until the evaporator temperature drops. With the evaporator fan not running, that wiuld cause the compressor to cycle more frequently that it would with the fan running and adding load to the system.

Secondary protection is provided by the limits of the compressor pump. As temperature drops in the evaporator, the suction pressure in the compressor drops. The expansion valve helps this by restricting liquid flow into the evaporator. Depending on more than a few factors, the system will reach an equilibrium point and hold there, still pumping a minimum amount of gas. The critical factor here isn't so much the gas flow, although there is some cooling of the compressor by the traveling gas flow. You need to have flow adequate to maintain lubrication in the compressor, and then it's a factor affected by the amount of gas in the system, the amount of non-condensible gases mixed in, ambient temp at the condenser, and the actual heat load at the evaporator.


Between these two protections, you shouldn't sweat possible compressor damage, especially if the abuse is not extended.

JayPoorJay

Hello All. Calling up this old thread...

I went in and removed the fan and stuff to get to the resistor pack. My problem was that one of the 4 wires in the resistor was burnt making it so speeds 0, 1 and 2 supplied no power (I think) to the fan. Only 3 and 4... Also, the fan appliance was gummed up and it took a LOT of amps (never measured exact) to turn it. I freed up the fan axle with some marvel mystery oil and replaced,,, at the same time made some adjustments wrapping the burnt wire over itself for contact (wouldn't take solder,,, something to do with the resistor wire NOT liking solder)... Anyways, on reconnect,,, fan flowed nicely on 0 and now worked on 1 and 2. Great!

Silly me - I didn't like the wrapped wire "fix" that I had come up with. It felt COMPLETELY temporary... So,,, brain I am,,, I took a spare resistor pack from an 85 and put it in line,,, buttoned everything up. NOW,,,, MBS!!! Like crazy!

QUESTION --- does (has) the removal and capping of lead 8 on the connector work without causing damage? Have any scary reports come back since this solution? I worry about frying another pack IF it doesn't have this safety function. What happens when it overheats??? I ran some little tests when I had everything apart,,, and on some of the dash settings the resistor wire get RED HOT quickly without the fan and yes,,, the fan does good work to regulate some serious heat in the tunnel...

I don't have a 12yo with a skinny arm and I'm lazy! Does capping lead 8, work? OR,,, do i needto take this whole thing apart again?

What say you?

Darklands

The resistor pack isn't so expensive so I change it in the afternoon.
Putting a NEW Motor in the blower and all is readly for the next 25 years.

Old and broken.The screws are a pita. I use copper anti size.


New motor from Roger, perfect fit. The axle is a little bit longer than original.

The bearing is broken.

Cadillac art

Any reason this quick fix needs to be temporary only? In other words, is bypassing the "magic blower circuit" as Porken described going to cause the resistor to dangerously overheat? Based on the reputation of the original poster I suspect this is an okay modification.

PorKen

Note the OP was a just a punk 928 fan in 2003.

Best practice is to replace the fan motor (a replacement for the motor only has been found and is available) and resistor pack. That said I have (embarrassingly) usually driven for many years with the quick fix on all of my 928s.

As I recall, there is a thread about bending the bi-metal sensor inside the pack to reduce/restore its original(?) sensitivity.

I had forgotten about the [0] off hack. Thanks for the refresher!

Cadillac art

Thanks. I'll tackle it sooner than later then. In the meantime- thanks for the quick fix!