Fan turns off when key turned off!

Good evening-

I don't usually like to bug other people with my problems, but I am at my wits end trying to troubleshoot this car problem. I'll outline the problem, and then maybe you can make sense of it.

-The car is an Oldsmobile Ninety Eight

-History: two weeks ago, the car wouldn't start; electric power was intermittent. I traced the problem to corroded battery terminals, after which point the car worked fine. Before that trouble, the car underwent regular periodic maintenance.

-The Question: As of last night, the cabin blower fan and dash display will not turn off when the ignition is turned off and the key taken out. In fact, the blower fan will actually come ON when the key is taken out, even if it was previously off. The Temp indicator on the central dash/climate control console flashes, also. The fan can be turned off with the climate controls, but the display is still sucking juice. Also, the driver's side console warning display indicates that there is a coolant problem; however, I did not find any evidence of coolant leakage.

This car is driven by a friend of mine, and I can't really give any insight into her driving habits or what she might have done to cause this. I really don't know much about onboard diagnostics, and I really don't want to shell out a lot of money just to have someone hook up the car to a PC. I will do what I have to do to get the thing fixed, of course, but I'd like to take the cheaper route.

Any insight you might have would be greatly appreciated.


Cheers from up North,
Ben

Welcome to AF. Please post the year for more accurate help. The fan issue is usually caused by the blower power module, again location depends on year.

I have a 1989 Olds 98 Regency, mine started doing the same thing recently. I had to pull the connector off of the back of the blower fan (in the engine compartment, on the firewall) in order to stop the fan from running with the engine off. After some troubleshooting, I determined that the fan was getting its power from some sort of module, mounted inside the air duct. Yes, I found that the module has 2 connectors, one with 1 wire (red) and one with 3 wires. The module has 6 pins, but only 4 of them are used. The purple wire on the 4-pin connector is spliced into the purple wire that is the power wire to the blower fan. The red wire, on the 2-pin connector is hot, connected to a small bus block mounted above the module, on the firewall.

I found 100% continuity between the pin which the red wire connects to and the pin which the purple wire connects to, which means, 12V all the time to the blower power wire...so I concluded that module must be the problem.

I took it to my local Napa store, they looked up the Delco part number printed on it 16061602 and could find NOTHING. I tried another parts store and they also could find nothing. Since I didn't know what the module was called, they had trouble just looking up the part in their databases.

Finally, the Napa store checked with a local GM dealer and they identified it as a Blower Control Module, or AC Control Module.
Napa used that name and looked the part up for me, and found something.
Today I went to their store, and before buying just checked resistance across those two pins (red wire and purple wire) to confirm that it was not like mine, a solid connection. There's showed about 4 ohms resistance, which was good enough for me, confirmed that my part was bad.
So I bought it $208.00. Yikes, at that price I didn't want to be installing parts for troubleshooting, I wanted to be sure.
Well, after installing, the blower fan issue is fixed...it works as it is supposed to and doesn't blow all the time.
However, I discovered a new problem, now my AC does not work...it just blows hot air continuously. It worked great before this problem occured...
While I had it running I looked under the hood...it sounded like the compressor was switching on and off, repeatedly at short intervals, the engine RPM was constantly changing to adjust for the compressor, and the accumulator was warm---except one line was cold with condensation on it.
I am quite certain this NEW problem is related to the new part. Perhaps they gave me one meant for a different configuration of components or something. They never asked me about all the details of my car when they brought this part in for me.
And also, the new part looked slightly different than the original. It had the same overall dimensions and mounting areas, connectors, etc. But the heatsink was a different shape and it had some additional round component attached to the heatsink--but still remained within the original dimensions as I said. I just figured the replacement part was modified from the original, as often happens in an 18 year old car.

Any ideas about the AC issue? All indications inside the car are normal, AC turns on, you set the cold temp you want, the fan blows, the compressor clicks, engine RPM decreases, etc...but no cold air. As I said, it worked fine before the original module failed.

Really disappointing since I'm stuck with this $200 part.
I had considered a simple, cheap repair, that is just splicing in a simple switch in the purple blower power wire, leaving the old module in place.
Now I may end up having to do that anyway....unless I want to cough up another $200...
We'll see.