• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

1995 A/C controller question

SnowDrift

SnowDrift

Ultra Conservative. ULTRA!
Messages
3,056
Reaction score
3,785
Location
Central Ohio map dot
I've heard these are prone to fail on the '95 models. I think I've been nursing mine along for about 10 years and some features never really did work right. Today I fired up my truck and heard a noise under the hood. It turns out the clutch on the pump was on, off, on, off, on, off, etc. I ended up pulling the fuse to get it to quit. Shall I assume my controller in the dash has given up the ghost and is causing the circuit to go on and off, repeatedly or is there something else that could cause this?

I didn't have the A/C turned on, either. Button was in the off position. cycling the switch changed nothing.
 
The blower switch is bad. GM has a TSB to replace the blower switch separate of the control head for this problem. BigT just did his.
 
Thanks, guys. I had forgottem about the extra ground I added, but when I read about the melt down wire set, I remembered I had worked on some of this before: http://www.thetruckstop.us/forum/showthread.php?24689-No-Blower-Motor-at-any-speed

I read the post from your link, WarWagon. Interesting stuff. I'll also look for the TSB mentioned above. Do I understand it right that you're saying the switch, itself can be replaced, but it might be a good idea to consider replacing the whole panel due to the materials becoming brittle over time? Incidentally, where did you find that control for just over $100? I priced one from LMC for $219 last night.

Mine cycles with the blower on. I haven't tried to see if it does so with it off, but will check today.

When the recirculation button is pushed, the light has come on in the past (haven't checked to see if it's still doing this), but I didn't notice any change in airflow by pushing the button, itself. Occasionally while the A/C was on, though, it would randomly sound as if it got much louder than normal, but the fan didn't kick up. I assumed this was because the recirculation activated and the airflow path changed, causing the noise to be different. I've never been able to activate the recirc. function, to my knowledge. Will this be affected by a switch change, as well?
 
Last edited:
The pics of the melted connector would be useful in the control head thread.

With the fan speed set to anything but off you can turn the temp down to the coldest and the recirculate light should come on. Same with pushing the button. This light is a "command given" indicator. The door could respond or be broken and not respond. Mine flopped all over with the light on due to a bad actuator. If the light doesn't turn on the control head is bad. Hot cold can also be a problem with the control heads going full heat in the cold position.

At this time you should recheck the connector repair under the dash. Again mine burned up a second time due to a high current blower motor. Repair if necessary than re-check the functions of the control head before replacing. Check the grounds as well including from the body to the engine/battery. Most likely the control head is done, but, eliminate the cheap grounds and power issue.
 
WarWagon said:
The pics of the melted connector would be useful in the control head thread.

With the fan speed set to anything but off you can turn the temp down to the coldest and the recirculate light should come on. Same with pushing the button. This light is a "command given" indicator. The door could respond or be broken and not respond. Mine flopped all over with the light on due to a bad actuator. If the light doesn't turn on the control head is bad. Hot cold can also be a problem with the control heads going full heat in the cold position.

At this time you should recheck the connector repair under the dash. Again mine burned up a second time due to a high current blower motor. Repair if necessary than re-check the functions of the control head before replacing. Check the grounds as well including from the body to the engine/battery. Most likely the control head is done, but, eliminate the cheap grounds and power issue.
Click to expand...

Good idea on re-checking the connections. They're still good. I was also able to verify the extra ground wire, as well, since I had forgotten about it, except for when I read about what I had done a couple years back. I've only ran the fan on the highest blower setting one time and that's when I burned up the connection. This thing has so much wind, I could blow dry my hair on the lower settings.

Good idea on using the photos for the thread you mentioned. If someone can load them, have at it. The computer that has all my photos is in the shop and I'm not sure, at all, when we will have it back. Bad motherboard.

I tried to duplicate the scenario today and had limited success. At first, I could get it to duplicate. I had the A/C button on and the clutch would be on, off etc. I turned the fan off and the A/C disengaged, then turned back on when I turned the fan back on. Although, I couldn't try as many times as I wanted to, it seemed that the two times I got to try it, the flip flopping clutch stopped once I turned the fan to a higher speed, other than the lowest setting. After I did this twice, I couldn't get it to act up anymore, no matter what I did. The lights functioned as they should, although I didn't notice what they were doing while the clutch was flip flopping. I believe it was on constant, though, if I remember right from yesterday.

Do you think I'm facing a fan switch or the whole control unit, at this point?
 
Test the rec door. fan speed on low. You should be able to look up from the floor and see it move.

The clutch coming on with lights flickering is the blower switch. It is for sure done. Now the other stuff may be failures in the rest of the control head.
 
recirculation door operated today. I tried it manually, by pushing the button to activate it and also by way of the fan switch set to the Max position where it activated automatically. I've not experienced any flickering lights since I've had the truck. I'm leaning toward the whole controller, at this point, unless there is a reason I should not be. I'm not crazy about spending the extra $ in the event the switch would have fixed it, but I don't want to throw money at a new switch, either, and still have the same problem. What's your thought on that, WW?
 
As TheFermanator noted, I just changed the switch out on mine. Pretty simple job and I just did the switch not the whole control panel. AC Delco Switch was $17 with shipping from Rockauto. Entire control panel was $134 before shipping. I would try the switch first.

WarWagon talked me through testing the old switch. Took a jumper wire from the brown wire at the switch plug to the other contact points and the fan motor worked at all 4 speeds. So I knew it was the switch.

Control panel is accessed by prying off the dash bezel, then popping loose the two sides of the control panel by using a screwdriver to pry the locking tabs inward. Then shimmy the thing out and upward and remove the various plugs. One hex head screw holds the AC switch in. Done. Reverse to install.

The clutch going off and on without the switch could be the result of the AC system having lost its charge. My '99 did this last fall and my compressor was leaking. Installed a Sanden and recharged the system and all was good until I lost the switch. Replaced the switch and I'm back to having ice cold air blowing at me.
 
Thanks, Big T. I'm thinking the control head, itself might be the culprit in this. The lights don't ever flicker and it's gone from fresh air to recirc. on its own since I bought the truck. I drove it yesterday, too, and didn't have any trouble at all, so the problem is intermittent, at best, which is why I suspect an electrical problem.

Thanks for the tips on removal. I've heard they're a pain to get out without breaking tabs.
 
Our (now wrecked) '95 Suburban did the same thing: switch back and forth from recirc to fresh and clutch cycle on and off. The system had lost its charge. The control panel automatically goes to recirc when the blower switch and AC temp are both on full, but a low charge in the AV system won't keep it there.
 
The cycling off and on rapidly with the system off is because the fan switch has 2 outputs. One side powers the fan through the different fan speeds, and the other side powers the A/C control head. The fan switch can fail and power the A/C with the fan not running. And when this happens the A/C will cycle rapidly because there is no air going through the evap so it rapidly cools and heats with no airflow causing the rapid cycling. And I know it has been mentioned, but it cannot be stressed enough how critical the grounds are for the A/C mode door motors. Also GM screwed up and put the wrong recirc motors in some, so it could also be that.
 
THEFERMANATOR said:
The cycling off and on rapidly with the system off is because the fan switch has 2 outputs. One side powers the fan through the different fan speeds, and the other side powers the A/C control head. The fan switch can fail and power the A/C with the fan not running. And when this happens the A/C will cycle rapidly because there is no air going through the evap so it rapidly cools and heats with no airflow causing the rapid cycling. And I know it has been mentioned, but it cannot be stressed enough how critical the grounds are for the A/C mode door motors. Also GM screwed up and put the wrong recirc motors in some, so it could also be that.
Click to expand...

This ^^^^^^^ is spot on. Exactly what happened with mine.
 
where are these grounds? I don't remember reading about them in the past, aside from the blower motor extra ground WW recommended.
 
SnowDrift said:
where are these grounds? I don't remember reading about them in the past, aside from the blower motor extra ground WW recommended.
Click to expand...
That is the ground for the whole A/C system on the 95. GM changed this later on, but for 95 they used that one blower motor ground for the whole A/C system. And even a SMALL amount of resistance in it will make you think the control head is bad.
 
The blower motor threads into plastic. So the ground on the blower motor is "from" the motor through the melt able connector to a ground somewhere else. The motor is only grounded through the connector wires. This is why you add the extra ground wire from the motor to a good ground.
 
Thanks for the explanation, guys. The extra ground makes a lot more sense now. Come to think of it, I'm not sure if I've heard the recirculation door operate on its own since I put that extra ground wire on a couple years back. Maybe that was some of the troubles I was having on that issue. I am planning to get the switch, to start with to see if that fixes the cycling issue.
 
I put in the new switch today and have not been able to drive it yet. Friday, the A/C wouldn't engage at all and would only blow warm air. Later that day, it would engage. Today, after the switch, it engages. I'll post back in a couple weeks as to whether it works consistently or not.
 
You must log in or register to reply here.
Back
Top