goodson

I have the electronic climate control on my 86 and the indash control module has gone bad. It seems to work except that the fan won't come on. Since this particular module is expensive, I was wondering if I could connect either a on/off switch or a varible resistor switch to vary fan speed. I have verified that the fan works ok. If I can do that, what wire guage and fusing should I use?
Thanks!

SunCr

I don't know if it would work, but you would need at least a 25 amp switch and an appropriate fuse. I'd check to make sure the module is powered up first. Fusible link provides battery voltage on the red wire at the module (top of Evaporator housing - check for 12 volts). Blower signal from the dash is on the brown wire in the connector next to it. It should have about 6 volts at the highest fan speed. Output on the purple should be at least 12 volts at the maximum setting. Check ground to frame too. Blower module and the motor share this ground. Find the splice by tracing the black wire from the frame through the loom, back to the module.

goodson

On the RED (2 pin) (power thru fusible link) I have 12v standing. On the BROWN (4 pin) (blower signal from the dash) I have 12v rather than the normal 6v or so. I don't have a purple wire (4 pin = black/red, brown, black, green/yellow). The black/red (4 pin) (output to the blower motor) = ov. I also verified the ground continuity at the module (black) and at the blower motor (black). Also, I can jumper the RED (2 pin) to the BLACK/RED (4 pin) and the blower motor runs.

What is confusing me is that I don't know exactly what the blower module does. In other words, I want to be sure that I don't have a problem with it before I replace the control head. The blower signal from the control unit has 12v instead of 6v or so, but why would this keep the blower from running?
If you could explain to me what the blower module does and how to test it, I would greatly appreciate it.

Another question: Do you think running a fused wire direcly from battery to the blower with a swith on it would work to run the blower? I assume the blower works on 12v and the speed is varied by current thru a varible resitor (switch). Is that correct?

I appreciate your help tremendously

SunCr

Module is more or less an amp as far as the blower is concerned. It takes low voltage signals from the dash and applies a variable voltage to the blower. It also completes the circuit for the a/c clutch (green wire) by suppling a ground when it receives a low voltage signal (green/yellow wire) for a/c - does the a/c work? Brown wire is the blower input from the dash with a range of 2.5 to 7 volts. Module provides an amplified voltage of 4 to 12 volts to control blower speed. Procedure for checking the max setting is to back probe the module connector for the 6 volt signal; then if you have the six volts and blower doesn't run, repeat the test with module disconnected. If the voltage is now above 6 volts, the blower module may be bad, but first check the 5 amp fuse on firewall. That protects the voltage signal back to the dash assembly from the blower motor (there should be another splice from the hot side of the blower motor harness for this wire - which on yours is apparently black/red). The dash assembly needs to know what voltage is actually being provided to the blower for it to operate correctly. If the fuse is ok, it's probably a bad blower module. If you continue to get 12 volts on the brown wire regardless of connection, check for a short to battery voltage - unfortunately, if that is the case, that may have blown the module. Running a fused line directly from the battery to the blower will certainly make it run.

goodson

With the 4 pin connector plugged into the blower module, I get 1v on the brown lead regardless of conrol unit setting and also even with the ignition switch off. With the 4 pin plug disconnected and ignition switch off, I get 0v and about 2k ohmns to ground on the brown lead. On the module end, I get 4 1/2v (switch off). With motor running and air on on control unit, I get 12v on the brown lead and 12v on the module end. Taking it a step further, I disconnected the control head and got the following readings on the brown lead (unplugged): 0v and 0 ohms grd with ignition switch on and with switch off. Does this appear to be a blower module problem?

I couldn't find a 5 amp fuse on the firewall. I did check the 15 amp fuse to the blower. There is a connector attached to the side of the blower housing that has ped 7 on it. It has 4 wires going into it (faded but appears to be w/sl, bk, y, bl). Is this a fuse or what?

One last question, Is the blower module simply attached to the evaporator housing with the 3 screws? I removed the screws but the module seemd to be secured against the housing. I didn't want to be too rough with it without knowing for sure.

Again, I really appreciate you taking so much time to help me with this!

SunCr

Power to the blower motor is not fused - there's no fuse at all. For electronic air, the protection is a fusible link which powers up the module. For manual air, the link is in line with the relay. For electronic air, the hot lead to the blower is spliced to another lead that sends a return voltage back to the dash assembly. That circuit is protected by a 5 amp fuse mounted on the firewall near the evaporator. Follow the power wire from the blower motor through the loom to locate the splice and then from the splice to the fuse. Now if someone stuck a 15 amp fuse in this circuit because the 5 amp fuse was blowing, the dash control is probably shot. Power to the dash assembly is through the courtesy clock fuse (memory only) and Gages fuse. Check these fuses if you haven't all ready done so. No voltage on the brown wire sounds like no signal from the dash control and/or a short to ground on the brown wire. The dash assembly grounds should be checked too - there are 2 which take a different path to the ground located in the driver's side footwell. One is spliced into the interior harness that leads to this ground (anything else not working - like the wipers, door locks, courtesy lights? They all share this ground path). The other takes a direct path, so you can at least verify that there are two wires on the lug at this ground point. The other connector you reference sounds like the electronic spark control module.

SunCr

Forgot to add that the module is sealed to the housing (to keep air from escaping and water from getting in). It extends about 6 inchs or so beyond the mounting plate inside of the housing. Use a putty knife to break the seal. There's really nothing to diagnose beyond what you get at the terminals though. Do be careful with the attachment screws - it's easy to strip the threads in the composite housing and sometimes they'll strip because of sealant on the threads. If that's the case, you'll need to go to the next larger screw size when you reinstall it (keeping in mind that you can only do that about once before you have to drill out the module mounting plate).

goodson

My mistake! It is a 5 amp fuse - don't know what I was thinking. The brown wire (blower input from the dash) is clean to the female plug in dash (no shorts,ground). I'm assuming the dash unit is bad as far as fan operation goes since the brown wire has a constant 12v rather than the 2.5 to 7 volts. Even if the dash unit was receiving the wrong or no signal from the blower module, it wouldn't put out more than 7v on the brown lead would it? I'm assuming the blower module is probably ok but not certain.

I did straight-wire the fan through a 25 amp fuse and under-dash toggle switch. I'm sorta back to where I was before the complete failure of the fan. Previously, I had intermittent fan failure and then it stuck on one speed until final failure. The control head is completely functional except for the fan. The temp control does manipulate the temperature even with the constant fan speed. Is the Blower module involved with the temp control? I may just go with this until I get additional failures from the control head.

Thanks again for all your help!

SunCr

You could try jumpering 6 volts from a dry cell to the input and see if the blower runs as another way to test the module. You'd probably have to take apart the connector, but I think that might work as long as you supplied a separate ground for the test battery. Module controls blower and ground circuit for compressor operation only. Dash controls temperature by varying blower speed and with the progammer, position of the plenum door that controls the flow of heat over the evaporator.