Hey guys,
I have a problem with my fan speed on my 88 w/ C68. When I start the a/c with the temp set at 70F the fan speed is at 10 and it blows a 10. After 10 minutes the fan slows down to about a 7 by itself but the display says 10. This happens on AUTO or Manual. The slow down lasts 2 minutes and then speeds up again to high or 10. I can't change it. Since it's been so hot outside lately I have noticed that this continues on & on for my entire 45 minute commute home.

I tried the diagnostic check in my 88 manual but I get no information displays on the unit. The only thing wrong with the C68 is the outside temp which is always wrong by as much as 20 degrees(low). The inside temp reading is OK and stays where I set it. Is it the unit or the blower control module?

Hope you can help and I appreciate what you do for us shade trees.

Jim Campbell
had2hav2@aol.com

 

......never heard of this happening at all. i have an 88 also...is there a temp sensor on the horizontal pillar near the back of your head at the drivers side?...since that is supposed to sense the temp of the cockpit, ya think that could have something to do with all this?...i imagine just the interior temp but, worth giving it a glance..(i don't have helms handy).

..my vote is in the heater housing in the engine bay on the top, you'll see a "plug" that attaches to a fan control module which i believe mounts with 2 small bolts......ck your connection there and if all appears right, i would suspect that module is going bad......

 

How are you judging the fan speed slows down to 7 when it is displaying 10?

One thing to keep in mind is most climate controls automatically switch between "recirculate" or using outside air depending on the difference between inside and outside temperature.
This switching between recirculate and outside air can make it sound like the blower speed changed when it really didn't.
Recirculate usually makes more noise at the same blower speed because you are hearing the air being drawn into the system under the dash as well as the air coming out the vents -- when using outside air, you only hear the air coming out the vents, which isn't as noisy.
So, if you are judging blower speed by the sound, it may be deceiving.

Since you are saying your outside temp display is always incorrect, if that is true, the climate control may be confused and switches to and from recirculate when it shouldn't.


Tom Piper

 

ReCirc is suppose to only occur at Auto 60 and when the Controls are at that setting, the Blower should remain at Max. Otherwise, Blower Speed is controlled by inputs from the Inside and Outside Sensors and whatever you've dialed in above 60. If you want it to remain steady, you're suppose to use the Manual Fan positions, though Manual 10 will not get you Max (on these earlier Years) - that's only suppose to occur at Auto 60. Mine - in recent Years, will sometimes toggle back from Max to Manual 10 even when on Auto 60 - something it didn't do when it was new. I assume it's either in the Blower Module or the Controls, but it isn't worth it (to me) to spend a lot of time troubleshooting it. In any event, if either of the Sensors (Outside or Inside) are off, you will get different results and I don't know what is Programmed into that Controller, but I'm pretty sure there's some "Dilbert" Engineering involved. My guess - for your Unit - is that the Inside and Outside Sensors are sending "it's really hot outside and inside" voltage signals and you're seeing Max fan even when it's on something above Auto 60. As the Inside Sensor cools down, it then lowers the Fan to the 10 Speed. Once that happens, you might try putting it on Auto 60 and see if that doesn't pump it back up. If it does, it's somewhat normal.

 

About six months ago my outside sensor was damaged, ordered a new sensor from Ecklers or Mid-America do not remember which. Prior to the installation of the new sensor the car would cool as normal then out of no-where the blower would drop to lower out put, then at times heat would come on. Lights flashed on the controls also. Pulled the fuses as the owners manual stated, disconnected the negative terminal from the battery, disconnected the outside sensor. Waited five minutes the reconnected in this order.
1.) outside sensor
2.) re-connected the battery
3.) re-place the fuses you pulled (old ones unless damaged)
4.) Start the car, place the climate control on auto 70*

Works perfectly

Hope this helps

 

Thanks for the hints. I have one vote for the outside sensor and one for the module. I think that is about $200 total for both.

Tom Piper: fan speed is a judgement call. No #7 shows up on the display. Unit functions normally except for the rush of cold air that lasts 10 minutes. Sure beats my 76 Stingray A/C fouled up or not.

SunCr: Does sound like ReCirculate. Not sure that this is suppose to happen all the time though. I'll try the auto 60 tomorrow. It will be
100F so no problem wanting to be cool.

Da Mail Man: No sensor above my head rest.

I'll let you know tomorrow. At least it works. Charlotte, NC is like Satans vacation spot now.

 

....i didn't say that!.....it is in the piece that is part of the car behind your head.....i have it in mine and is the sensor for the inside temperature....

 

Basically, I just wanted to point out that there are 2 "10's". The one you get at Manual 10 is a lower speed than what you get at Auto 60 or whenever the Controller senses a need for Max Cooling. It's briefly outlined in the Owner's Manual (the Shop Manual is somewhat vague, though 1C1-4 has a Chart showing that the Blower Speed should continue to increase from Manual 1 to Auto when at 60). If you're really curious, you can check the various inputs and outputs at the Blower Module on the left side of the Evaporator Case. Input is usually Tan - output is Purple or whatever is hot at the Blower Motor. Range should be 2.5 to 6 or 7 volts on the input. 4 or so to 12 volts on the output. You could also check the resistance of the two Thermistors - Inside and Outside Temp Sensors at various temperatures, but not knowing the programming for the Controller, I don't think you'll be able to determine if it's working right. There is also additional information - including coding for the signals from the Inside and Outside Sensors that can be spit out from the Panel, but whatever that stuff means is greek to me (I presume it's Binary Code).

 

Hey Guys,

Found the inside temp sensor location. No damage there except by a hot sun (the bow is black) on the exterior. I have one last question and I will go away(I am buying a 07 base model with a paddle shift tomorrow). Good price. No trade on the 35th AN, I'm keepin' it for a while. If you know a good place to advertise a for sale feel free to say so. I might later.

I cannot get the unit into the diagnostic mode. I follow my electric mannual and all I get is two zeros. When I let go of the buttons it goes back to the inside temp setting. My quess is the unit. Any other suggestions?

That 07 is sweet. My first new one.


Thanks again

 

any body out there?