My 1988 Chrysler 5th ave has had some loss of vacuum to the HVAC system upon acceleration, resulting in very low airflow from the panel vents, and then letting off the gas the vent air returns to normal. I used a simple fix for this and so far it is working for in town and some highway driving. Here is what I did. I bought a Dorman #47076 vacuum canister ( $12.99 Autozone), Dorman #47380 vacuum connector assortment ( $7.99 Autozone) , 1'- 9/32" rubber vacuum line, 6'- 7/64" rubber vacuum line. I connected the 9/32" rubber vacuum line to the Dorman vacuum canisters larger port. I then used a 1/4" to 1/8" connector to reduce it. Then push on the 7/64" rubber line to the 1/8" connector end. Pull off the original 1/8" black rigid line going to the rear intake manifold multi port, and push on the new 7/64" rubber vacuum line to that port. Then push on a piece of the 7/64" rubber vacuum line to the smaller port on the vacuum canister. The other end gets pushed on to the original black rigid vacuum line you removed from the multi port at the rear of the intake manifold. This canister was chosen because it fits well under the hood, and was available locally. I left a little extra line to relocate the canister if needed. Note the temporary red twist tie. The round plastic ball is the new vacuum canister. All together the cost was about $25.00. I hope it keeps working.
HVAC system vacuum loss restored
- Thread starter Master M
- Start date
This was the exact same factory solution that Chrysler used on the late model Grand Wagoneers when they unified the heater, and A/C controls, and made it a vacuum actuated system. This big ball lived right on the Jeep firewall, and worked like a champ.
8v-of-fury
Well-Known Member
So, the ball just basically stores vacuum? Weird, i find my HVAC controls work better when i am cruising as opposed to idling.
Cordoba1
Well-Known Member
There's a vacuum check valve located inside the car, between the firewall and the HVAC push buttons. When the symptom is air flows out the heater vents upon acceleration, but returns to the upper vents when lifting off the throttle, the check valve is often found to be the culprit.
8v-of-fury
Well-Known Member
Sorry, when I said "Works better" I meant that they switch the doors or temperature faster is all. It stays on whatever selection you're on, but initially takes a while to get there.
Cordoba1
Well-Known Member
A ha! Got it.... Yes, a stronger and more consistent source of vacuum would certainly help in that department.
8v-of-fury
Well-Known Member
You'd think the 19-20 in/hg at idle would be the strongest vacuum though wouldn't you?
