Auto Air Conditioning & Heater Repair: 1979 Pontiac Bonneville blower speeds, pontiac bonneville, rotary vacuum

Question
I have defrost no matter what-telling me the blower is alright. I get all blower speeds and then lose all of them. No set amount of time as to how long I can retain blower or how long until I can get it back. The system is climate control and I already replaced the heater relay, rotary vacuum valve and the electrical selector switch. I already checked and the contacts are all fine. None pulled out, loose or dirty. I tried rapping the side of the programmer( I had it out to see if anything apparently wrong ). Found nothing. I lean toward thinking that there is a malfunction with it though however. I checked the resister and none of the wires are burned or separated.Any help GREATLY APPRECIATED. THANKYOU SINCERELY AND KINDLY. FRANK

Answer
There is a 3 or 4 wire electrical connector downstream from the blower motor POSITIVE wire. This connector tends to corrode internally and may look perfectly OK when viewed from the outside. I have had to eliminate this electrical connector and solder the wires directly to correct this type of problem.

The probrammer is usually NOT the cause for the blower operation as it's main function is to control where the air is directed from the different vents in the dash.

I belive they still used a BLOWER MOTOR HEATER TURN ON SWITCH of which prevented the blower motor from activating until th engine warmed up slightly so you would not get a blast of cold air from the system.


Look around near the front cylinder heads of the engine for a black single wire that attaches to a single spade electrical aluminum round switch. If this switch goes bad, it will stop your blower motor operation.

This switch is about the size of a dime and has a single spade electrical connector and simply threds onto the cylinder head usually in a recessed pocket near the cylinder head or is located next to the alternator.

You can either replace this switch and or simply remove the wire and GROUND the wire to any metal surface and by-pass this feature.

QUESTION: Is there a POWER MODULE located near the blower motor ?. This unit will have 1 single electrical connector and a 4 to 6 wire electrical connector attached to it.


autohelp