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A/C drops out under load/uphill...
- Thread starter wgregt
- Start date
Not normal. You have a vacuum problem, probably the line from the firewall to the vacuum canister(s)--not sure if the '88 has the "soup can" canisters under the hood or black plastic reservoir behind the front bumper. Could be the plastic line or the check valve associated with the reservoir.
Problem is, when you accelerate, vacuum decreases and the a/c doors default to defrost position.
Problem is, when you accelerate, vacuum decreases and the a/c doors default to defrost position.
Hmm...doesn't blow warm...not sure about it shifting to the defrost vents. I'll go for a ride now and check on that one...it just drops from 100% to 10% maybe tops in blowing force...makes it damn hot in there when I'm on the gas or uphill...
The canister is behind the front bumper, and all was fine with that when I had the bumper pulled for painting last year. I'll check the lines under the hood and also the defrost vents when under load as well...
The canister is behind the front bumper, and all was fine with that when I had the bumper pulled for painting last year. I'll check the lines under the hood and also the defrost vents when under load as well...
Double check on the defrost vent thing. If that's the case, then like Pelican said, you have a vac leak somewhere. The vents default to defrost when there's not enough vacuum. This can ofter occur when accelerating, going up hill and towing due to the low vacuum.
Check the the canister (vacuum reservoir) and it's lines. Also look under the battery tray as the vac lines pass below it. There are also a few check valves in the lines. A few have reported their issues were due to the CV failure.
Check the the canister (vacuum reservoir) and it's lines. Also look under the battery tray as the vac lines pass below it. There are also a few check valves in the lines. A few have reported their issues were due to the CV failure.
Checked it later today. Yep...air (hot air at this point...I think the ac compressor is gone) blows from the vents, then defaults to the defrost vents under load.
Damn this ac system. If it's not one thing, it's 15 others that'll cost me a wad o'bills...
I'll check the lines. Did not know about the battery tray thing, so that's good info too...CV?
Damn this ac system. If it's not one thing, it's 15 others that'll cost me a wad o'bills...
I'll check the lines. Did not know about the battery tray thing, so that's good info too...CV?
X2 on "CV"? Check valve?
When this happened on my '85, the problem was not the vac line but a failed check valve. Each of the two reservoir cans had an integral check valve so I just moved the line over to the can with the functioning valve and all was well. I'm not familiar with the valve setup on later models.
Most everyone refers to that vacuum line going under the battery tray but on my '93 it is routed beside the battery, nearby but far enough away to avoid the acid fumes. I don't know if someone did a minor mod or if later models came this way, but it might be something to do if you end up having to replace it anyway.
Of course, you appear to have bigger problems that the vac lines -- good luck!
When this happened on my '85, the problem was not the vac line but a failed check valve. Each of the two reservoir cans had an integral check valve so I just moved the line over to the can with the functioning valve and all was well. I'm not familiar with the valve setup on later models.
Most everyone refers to that vacuum line going under the battery tray but on my '93 it is routed beside the battery, nearby but far enough away to avoid the acid fumes. I don't know if someone did a minor mod or if later models came this way, but it might be something to do if you end up having to replace it anyway.
Of course, you appear to have bigger problems that the vac lines -- good luck!
CV=Check Valve.. Sorry.
The check valves (CV) "trap" vacuum in the reservoir for use during low vacuum periods (like listed above). If a CV is bad, when the absolute pressure in the manifold is higher than in the reservoir, the pressure rises in the reservoir, reducing vacuum and causing the vents to act up (switch to defrost) and can cause the cruise control to also work improperly.
Testing them is simple enough. Remove them and either blow (or suck) on each end (please spare me the jokes
). One way should pass gas, the other not (OK, you can joke now!). Another is to simply run the engine for a few minutes, then shut down (key off). Wait a few minutes, then operate the mode doors, switching from defrost to dash, to floor, to dash and so forth. You should hear the doors moving. You might get 5 or 6 changes before you run out of vacuum.
The check valves (CV) "trap" vacuum in the reservoir for use during low vacuum periods (like listed above). If a CV is bad, when the absolute pressure in the manifold is higher than in the reservoir, the pressure rises in the reservoir, reducing vacuum and causing the vents to act up (switch to defrost) and can cause the cruise control to also work improperly.
Testing them is simple enough. Remove them and either blow (or suck) on each end (please spare me the jokes
). One way should pass gas, the other not (OK, you can joke now!). Another is to simply run the engine for a few minutes, then shut down (key off). Wait a few minutes, then operate the mode doors, switching from defrost to dash, to floor, to dash and so forth. You should hear the doors moving. You might get 5 or 6 changes before you run out of vacuum.Found, checked (via the suck/blow method), and replaced one check valve that runs along the right fender. It was fully open both ways.
Could only find the one CV...is there another?
Replaced compressor, drier, and 2.25# of R12 (a real PITA to get here in CA). Nice and cold again, but still drops out going uphill or under load.
Hoses/lines to canister in bumper seem to be tight & good. No loose connections.
Could only find the one CV...is there another?
Replaced compressor, drier, and 2.25# of R12 (a real PITA to get here in CA). Nice and cold again, but still drops out going uphill or under load.
Hoses/lines to canister in bumper seem to be tight & good. No loose connections.
No apologies needed. Good question. The check valve I bought has a flat round side (that I put toward the windshield) and a pointed cone side (which I put towards the grill). I just copied the one I took out.
I think my next bet is just replacing the two hard plastic vacuum lines that run along the fender with rubber vacuum lines. These hard plastic OEM ones have been patched in a few places. Seems cheaper to just buy 12' of rubber line and replace them both. Anyone know the O.D. size of line I'd need?
I'm with you though: hoping it's not behind the dash somewhere.
Oh...any harm in swapping out the hard, brittle a/c lines and replacing them with just rubber line instead? The plastic ones seem to break just looking at them. I tried to move & reroute mine and one broke. I can see that they have been "patched" in many places already.
- Location
- Rainy side of Washington
I wouldn't put in rubber, it can collapse under heavy suction. But feel free to get some poly line from home depot or whatever your favorite source is and use that. I like the translucent clear 1/4" poly line they have in the plumbing and heating aisle, costs almost nothing and is rated for 150psi or more... accidentally found out that it'll handle 250psi when the pressure cutoff switch for my OBA compressor was shorted out!
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
The system isn't going to see anything huge in the way of vacuum, as long as the vacuum line/hose is designed for that level it should be fine. Hose will likely deteriorate faster than hard lines will.
- Location
- WA state
Pretty much all vehicles have a full throttle A/C cutoff switch.
But refrigerant may be low if it does not blow cold all the time.
But refrigerant may be low if it does not blow cold all the time.
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