QuestionHello. my 98 concord lxi, last month the air cond went out & it was overheating. i replaced the cooling fans and everything started working again. this month the blower under the dash will not shut off. it blows hot and then cold, last night it stopped blowing heat just cold air. it's 43 in the morning and it blows cold air? 2 weeks ago i replaced the windshield washer pump. and the blower under the dash still blows even with the switch off?. could you give me some input on where to start checking to fix this problem. Thank You for your time Mr.TC
AnswerOoops! I got mixed up and the answer I gave is for a van, not for your concorde sedan. Let me have another go at it.
Everything I wrote about the electrical concept is identical except for the control panel removal details and the plug details, and the resistor block is actually in the heater housing in a duct near the blower motor. So forget the glove box removal. Here is a copy of how to get to the resistor block which I wrote to another questioner. The wire colors are correct, but if you find that the black/tan wire is grounded then I'll have to tell you about removing the control unit in your car. If you want to kill the fan for now, pull 25 amp fuse #C1 in the fuse box under the dash.
"You can access it (the resistor block) by removing the lower right under-dash panel (it pulls down, but I am unsure about whether there are fasteners or not) to give you access to the blower motor on the underside of the unit To the left of the blower housing you will see a rectangular panel with wires protruding from it. That is the resistor block and the main body of the module (the resistors) are on the other side of the panel so as to be cooled by the air in the duct. The block is held in place by two screws which when removed will allow you to remove the block. Unplug the two plugs from the block and get a new one from the dealer. I don't know the cost. If you are electronically knowledgeable it might be possible to replace the burnt out resistor(s) but I have not tried this myself."
Roland
Hi TC,
The heater front blower is "set up" to run anytime the ignition switch is on because there is 12V applied to one of its wires (dark blue) from the relay located in the power distribution center (rectangular box) under the hood. So at least you could stop it from blowing by removing that blower fan relay, temporarily until you can find out why.
The motor will then run at variable speeds or full speed when the other wire of the motor (black/tan) is shunted thru the control switch to the ground (the - post of the battery, via the body return path). The possibilities are that the fan control switch in the control panel is shorted to ground all the time or that the wire from the blower motor to that switch is shorted to ground.
You have two ways to go to find out why the black/tan wire is grounded. One is to remove the glove box so you can get access to the wire and the electrical plug that it attaches to. Then you could try shaking the harness on the plug to see if there might be a break in the insulation that has grounded the wire and if it is nearby repair the break.
The other is to remove the control unit and examine the fan control switch to which the wire is fed to see if it has been shorted to ground at all positions. To do that you have to remove the cup holder. Then notice a thin rectangular panel just below the heater control unit; insert a tape-protected screwdriver tip in the upper edge of that panel and gently pry it out, being careful not to crack it or damage its retaining clips. There you will find screws that you remove so as to release the lower edge of the bezel that surrounds the radio and control panel. There are two screws above the radio that retain the upper edge of the bezel so you remove them and now the bezel comes off. Then you can release the screws that hold the control panel in place and remove the heater/ac control panel and unplug its plugs at the rear. You then can test the incoming black/tan wire to see if it is grounded. If it is, the reason may be that the tan/black wire on the plug is grounded because it is attached to the black/tan wire when the plug is inserted in the socket. That tan/black wire goes to a "resistor block" which is a set of resistors mounted in the firewall above the glove box (far upper right corner of the firewall) which is placed in that location so that the heat from the resistor in use to reduce the fan voltage to provide lower speeds will be safely dissipated in the incoming air flow from the underwindshield air intake plenum for the heater/ac system. So you may find that the resistor block has shorted out, but I doubt it, because the fan switch should still shut off the fan, unless the tan/black wire was shorted to ground by the failure of the resistor block. So you could pursue that possibility OR you can test the fan plug-in socket at the back of the control panel to see if black/tan wire from the fan motor is grounded no matter where you have the switch set (in this measurement the ground point would probably be a socket on the rear plug-in where a black wire on the now detached rear plug is normally routed when plugged in (the plug I am describing is the one directly behind the fan switch which is semi circular in pin array)). If so, then you need a new switch or at least examine why it it grounded all the time and repair it. Sorry this is so complicated but that is the way it is. I am using the Haynes manual as my reference and can send you a couple of pages that show the wiring diagrams for the system.
So in one way or the other you need to find the false grounding of the black/tan wire which is why your blower runs all the time. If you fix that problem then see if the heating and cooling control starts to work properly again. If not let me know and we'll work on that part of the problem. I hope this will help you get started and also to successfully repair the short circuit.
Roland
P.S. You can use a volt-ohm meter to measure the resistance between any point and a shiney surface attached to the body (what is called ground) and if it reads 0 ohms then it is grounded. Or you can buy a battery operated contiuity testor that light a neon bulb if a point of interest is grounded.
