1991 HVAC question
Thread Starter
Pro
Joined: Mar 2008
Posts: 579
Likes: 2
From: High Bridge New Jersey
1991 HVAC question
and the fun continues...as I was reassembling the DERM and CCM modules today, I remembered that the AC vents did not blow well, so I pulled the plastic duct and found 2 issues.
1) Main problem, everything comes out of the defroster outlet no matter what the control is on, A/C, heat, etc. The LED lights are on the control head but I hear no "whooshing" vacuum type sounds as you would normally expect. Quick visual inspection on the interior seems to reveal no issues with vacuum or electrical lines, and the 3 "doors" move by hand.
Where to start troubleshooting? Could it be a bad control head, servos, vacuum controls,?? The FSM seems to point to a "programmer" does the electronic C68 system use this part?
2) I pulled out a few handfuls of insulation(? looks like carpet padding) from the main center vent it was clogging the entire duct. I'm not sure how exactly it got in there in the first place (though I suspect the butcher "mechanic" who messed up this poor car big time) so I am wondering, A) do I need to put this stuff back in? (I know, not back in the duct!) & B) if so, where does it go?
thanks all
1) Main problem, everything comes out of the defroster outlet no matter what the control is on, A/C, heat, etc. The LED lights are on the control head but I hear no "whooshing" vacuum type sounds as you would normally expect. Quick visual inspection on the interior seems to reveal no issues with vacuum or electrical lines, and the 3 "doors" move by hand.
Where to start troubleshooting? Could it be a bad control head, servos, vacuum controls,?? The FSM seems to point to a "programmer" does the electronic C68 system use this part?
2) I pulled out a few handfuls of insulation(? looks like carpet padding) from the main center vent it was clogging the entire duct. I'm not sure how exactly it got in there in the first place (though I suspect the butcher "mechanic" who messed up this poor car big time) so I am wondering, A) do I need to put this stuff back in? (I know, not back in the duct!) & B) if so, where does it go?
thanks all
Instructor
Joined: Oct 2007
Posts: 151
Likes: 1
You might first look at the three way check valve under the passenger side fule rail cover. The vacuum line sometimes comes disconnected or, the valve doesn't work. Usually, If the check valve is bad, your cruise control doesn't work either.
Question is, Do you have a climate control or, manual hvac system. more infor to follow after you respond.
Bob
Question is, Do you have a climate control or, manual hvac system. more infor to follow after you respond.
Bob
Thread Starter
Pro
Joined: Mar 2008
Posts: 579
Likes: 2
From: High Bridge New Jersey
I have the C68 electronic climate control
not the manual system...
I will check the vacuum connection, I have no idea if the cruise control works, I was not able to drive the car long enough before tearing it apart to find out...thanks...
Joe
I will check the vacuum connection, I have no idea if the cruise control works, I was not able to drive the car long enough before tearing it apart to find out...thanks...
Joe
Thread Starter
Pro
Joined: Mar 2008
Posts: 579
Likes: 2
From: High Bridge New Jersey
no vacuum
When I ran a test vacuum line from the plenum to the programmer it works. Now...
The problem is I can't locate the vacuum source under the hood for the programmer -- I am pretty sure it's a plastic line not rubber and I think it's wrapped up in one or more harnesses with wires..
Can anyone supply more information or possibly even pictures? The FSM isn't great with the vacuum routing pics...
Thanks!
The problem is I can't locate the vacuum source under the hood for the programmer -- I am pretty sure it's a plastic line not rubber and I think it's wrapped up in one or more harnesses with wires..
Can anyone supply more information or possibly even pictures? The FSM isn't great with the vacuum routing pics...
Thanks!
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Source should be at the rear of the intake plenum, right side, near the MAP sensor or fuel pressure regulator feed. If you don't find it there, start at the vacuum tank in the left headlight well, trace the line to the cruise module, and from there, it should head back towards the Distributor and the 3 way (one inlet - two outs) check valve. You're looking for something that looks like this: http://www.napaonline.com/MasterPage...One+Way+Vacuum
Thread Starter
Pro
Joined: Mar 2008
Posts: 579
Likes: 2
From: High Bridge New Jersey
no luck -- must be missing -- pictures anyone?
Apparently the HVAC vacuum connection on my car is totally missing. Not surprising since whoever the prior owner was abuse the poor thing.
Anway, I can see a black plastic vacuum line from the firewall harness going into the mass of electrical wires, the problem is I can't find the other end. So it's either broken or somewhere I can't find it. The FSM is no help here.
I have no check valve in sight (or out of sight), would someone with a 1991 be kind enough to post a couple of pics of the plenum source and the check valve (if there is supposed to be one) and most importantly the HVAC vacuum tube and source?
I really really really appreciate it, this is like the last thing keeping me from putting her back together and on the road...thanks all!!
Anway, I can see a black plastic vacuum line from the firewall harness going into the mass of electrical wires, the problem is I can't find the other end. So it's either broken or somewhere I can't find it. The FSM is no help here.
I have no check valve in sight (or out of sight), would someone with a 1991 be kind enough to post a couple of pics of the plenum source and the check valve (if there is supposed to be one) and most importantly the HVAC vacuum tube and source?
I really really really appreciate it, this is like the last thing keeping me from putting her back together and on the road...thanks all!!
Racer
Joined: Jan 2007
Posts: 274
Likes: 0
From: Muskogee OK
I'm not sure if there were changes from 90 or not, but my line runs from a connection under the MAP sensor, past the front of the distributor into the check valve. It then splits out to a line that runs behind the dist into the HVAC.
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