GMC Repair: 1998 Buick LeSabre Limited, thumb screws, buick lesabre

Question
The fan blower on my Buick will run sometimes and then quit,then after a few minutes it may run 5 or 10 seconds and quit. Then sometimes it will not run at all. Today driving home I set the temp to 60 which ordinarily make the fan run immediately and keeps running until that temp is reached, it came on about 3 seconds and quit and did not come back on at all.  It does not matter if it is set at any temp.  I tried it at 90 the other day and out of the blue it came on and ran for about 5 minutes and quit, came on 2 minutes later and quit. Is this possible a relay switch or a temp sensor. If either, where are they located? Could this be another problem?

Thanks for your time.

Larry James

Answer
Hi
First do you have automatic air or Manual controls?
Located Under the hood on the right (passenger side) fire wall is an underhood fuse and relay block. It is held on by 2 small thumb screws. The thrid realy from the passenger side is the Blower motor relay. The fourth is the High blower relay. From you symptons, I Do not Believe this is your problem.
I think it is the Blower motor controller, which is located under the hood just next to the Blower motor, in the center of the firewall. It has 4 small wires going ito it and 2 larger wires (Purple and black) coming out of it. The 2 latter wires go directly to the Bolwer motor. It has 3 small 7mm bolts holding it to the blower case. There is really no way of checking it other than seeing if the smaller wires are giving an input to the controller. If they are giving a signal to the controller from the buttons you push on the programmer (HVAC Control head),then the control module is faulty. If no signals are being recieved by the module, then the Control Head (the thing you push buttons on in dash) is possibally at fault.
Experience has had more  blower Control modules than other items in this system.
If Manual Air, It Could also be the blower relay (The thrid one in box) which is fed AFTER the module and goes to the Blower motor.
You can check this by making sure you have 12v going to the motor on the purple wire. If so suspect the Blower Relay.