goodson

Can anyone tell me where the heater blower motor relay is located? My AC/heater blower has quit after a long period of intermittent operation. I've checked the fuses, including the underhood fuse. I don't see any battery with a voltmeter at the red input wire at the blower. I've pulled the climate control module to check the contacts and for broken/loose wires. Everything else works from the module (air/heat/economy/etc) with exception of intermittent display which I had even when the blower worked. I don't see the relay in my Haynes wiring diagram. Is the battery feed to the blower directly from the climate control module? If so, is there a way to rig a blower switch without replacing the module?

Thanks in advance for any help!

goodson

Forgot to say its a 1986.

hz900

I know there is a module of some sort with relays on it right on top of where the A/C lines go into the firewall that controls the fan somehow. It is held in place by a couple of screws and when you pull it out it has what looks like some sort of heat sink. I have heard of these going bad and causing the fan to do weird things. Not sure if this is what you are looking for though.

nitrous1

I just replaced the blower motor relay on my 86 coupe last month. It is located on the passenger side of the engine bay, right next to the heater hoses where they pass thru the firewall into the heater core. It's about a five minute fix. I got a new relay from Advance Auto for about $10.00.

Dan

goodson

I find the 15 amp fuse mounted on the firewall where the heater hoses pass thru the firewall . Is that what you are talking about? or am I still missing the relay location? Can you describe what it looks like, how many wires to it? Also, how did you figure out that was your problem? Do you have climate control on your vette?

Thanks!

Ray Quayle

goodson, the way you describe it you are talking about the C68 Electronic Climate Control. nitrous1 sounds like he is talking about the Blower Relay on a C60. goodson, you don't have a Blower Relay, you have a Blower Control Module.

It's at the top inboard side of the evaporator housing.

goodson

Thanks so much for the picture! Is there a way to test the blower control module? I'm not getting power to the blower red lead with a voltmeter. I did notice a spike of voltage on the red lead when the engine was cranked. I'm assuming the blower motor is ok since I'm not getting any voltage to it. Is there a way to straight-wire it to check the blower motor?

Thanks!

hz900

You could jumper it to the battery for a second. I do not know how to test the module but from what I've read when they go bad the blower motor won't go off.

Ray Quayle

I've got the C60 Manual A/C in mine. When I ordered my Pace Car back in '86 the C68 Electronic Climate Control was not available in the convertible. Over the years, hearing of the problems with it, I'm almost glad I couldn't get it. I've never worked on the C68, so anything I tell you is what I get from the manual. If another posts with differing advise that has actual hands on experience, I'd go with that. I prefer to read the manual, then verify what I've read on an actual system before I give advise, but here goes.

First make sure you don't have an error on the A/C Control Head. Does the EXT TEMP light flash for 60 seconds when switching ignition on? If so, it is signaling a problem. Press and hold the Rear Defrost button, then press and release the Manual Up button. This puts you in Diagnostic Mode. A number from 1-9 preceded by a minus sign will be displayed indicating the Mode. Advance the Mode Number by pressing the WARM button. Display the contents of a mode by pressing the COLD button. Select Mode 8 (SYSTEM FAULTS) and display its contents. If 00 is displayed then no faults are present. If anything other then 00 let us know.

I you still need to check out the blower control stuff, here goes. It looks like the Blower Control Module has two connectors. A 2 pin and a 4 pin. The 2 pin has a dark green wire and a red wire. The 4 pin has a black/red, a brown, a black, and a dark green/yellow wire. The red wire on the 2 pin connector is always hot through a fuseible link, the black wire on the 4 pin connector should be ground. With a meter you should always read 12v between the red and the black wires. The black/red wire runs to the blower motor. If you were to unplug the Blower Control Module and jump the red wire from the 2 pin connector to the black/red wire on the 4 pin connector, the Blower should run. If not you have a Blower Motor fault, a wiring fault from the Blower Control Module to the Blower Motor on the black/red wire or a Blower Motor ground fault. If the Blower Motor does run when jumpered, reconnect the Blower Control Module, switch ignition to RUN and switch the A/C to AUTO and press the Fan MANUAL UP button for 10 seconds. Then measure the brown wire of the 4 pin connector on the Blower Control Module to ground. This is the input from the A/C control head and should be 5.5v. If it isn't, there is a problem in the control head. Also measure from the black/red wire of the 4 pin connector on the Blower Control Module to ground. This is the output to the Blower Motor. I suspect it will read 0v, but have a look.

nitrous1

My car has the manual A/C system, not the climate control. I didn't realize that the climate control system didn't use the blower relay.

Dan

Ray Quayle

Dan,
That's what I suspected from your post. The Blower Relay on the Manual A/C (C60), is normally open when Blower Switch is in the first 3 speeds and current flows through the Blower Resistors. When in high speed, the Blower Relay closes routing full battery voltage to the Blower through a fuseible link. This link is hot at all times so if the Blower Realy contacts happen to fail in the closed position, the Blower runs even with the key out. The Blower Control Module in the Electronic Climate Control (C68) take the place of the Blower Relay and the Blower Resistors. This is also the system that has the underhood 5amp fuse for the Blower Voltage sample back to the A/C Control head. Our C60 doesn't have this underhood fuse.

goodson

Thank you so much for the valuable information! I know it took some time to dig it out and post it and I appreciate it very much. I have both a Clymer and a Haynes manual but neither gives any information about the blower circuitry. I'll check it out tomorrow with the information you provided and let you know how it comes out.

Thanks again!

goodson

I ran the test you provided. I couldn't get the diagnostics to work on the control head - I've had intermittent displays with it for some time. I ran the tests at the blower control module. The blower would run when straight-wired as explained. I got the 12v between the red(2 pin) and black(4 pin). On the last part, after pressing the FAN MANUAL UP for 10 seconds, I get 12v rather than the 5.5v I should. From the black/red wire on the 4 pin to ground, I get 0v as you suspected. I guess this means that the Control Head is bad doesn't it? If so, do you know anyone who rebuilds them? The only one I have found so far is at Corvette Central for about $225.

Ray Quayle

Have you tried simply removing and disconnecting the Control Head, cleaning the connector pins and re-connecting? There is a single connector for the Control Head. Also the Head will come apart and there is a between board connector. Clean this up with a pencil eraser and replace. See what that does for ya.

goodson

I had previously accessed the control head out and removed the front panel. I cleaned the contacts with alcohol and a cotton swab. I didn't think about using a pencil erasure. Afterward, I got to thinking that those contacts are probably not making well (still had intermittient display) and remembered someone talking about using solder on them. I thought that maybe I should access it again and use foil to help make better contact. I didn't disconnect the control head because I couldn't figure out how the connector connected and I didn't want to break it. Looks like I need to take another look at it. Any hints on how to disconnect the control head? As I recall, there was a lot of plastic on the back and the connector catch/release wasn't obvious to me.
Thanks again for all you help!