Ported Vacuum Switch Temp Rating?
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Cargo Master
Joined: Dec 2004
Posts: 3,362
Likes: 22
From: Florence, SC
Ported Vacuum Switch Temp Rating?
1985 Ford F150
Carbureted 302 V8, AOD
Non-California emissions
The ported vacuum switch on my thermostat housing broke off and I am going to replace it. Can someone tell me what temperature rating it needs to be when it opens to allow vacuum through? I am getting confused trying to match it up because I don't see a part number on it and some of the after market switches have different temperature ratings.
The parts man over at my local Ford dealer doesn't even know what I am talking about, so that is no help.
Carbureted 302 V8, AOD
Non-California emissions
The ported vacuum switch on my thermostat housing broke off and I am going to replace it. Can someone tell me what temperature rating it needs to be when it opens to allow vacuum through? I am getting confused trying to match it up because I don't see a part number on it and some of the after market switches have different temperature ratings.
The parts man over at my local Ford dealer doesn't even know what I am talking about, so that is no help.
Posting Guru
Joined: Sep 2003
Posts: 1,192
Likes: 1
From: lino lakes, mn
its called a coolant controlled vacuum switch or CCVS and usually you can tell by the color but what does it go to? Usually one line feeds it and one is a vent with no hose and one goes to the component i.e. air cleaner,EGR,AIR pump ect. this may help some one find wich one it is or you can try to find the correct vacuum print on autozone's web sight to identify it.
Moderator
Joined: Jan 2001
Posts: 56,984
Likes: 2,738
From: Virginia
Yes, you need to know what it is controlling if you want to guess at a replacement. Some of these switches allow vacuum through at the setpoint(like a egr system would) and some block the vacuum at the setpoint(like a exhaust heat riser system would)
GM had a simple color system too, and I have it memorized. These two units always did what I wanted for most applications. It was on a 79 Monte carlo with a 305. The yellow one turned vacuum off at about 100 degrees and went to the heat riser in the exhaust, and the purple one turned vacuum on at about 100 degrees and it went to the EGR system.
GM had a simple color system too, and I have it memorized. These two units always did what I wanted for most applications. It was on a 79 Monte carlo with a 305. The yellow one turned vacuum off at about 100 degrees and went to the heat riser in the exhaust, and the purple one turned vacuum on at about 100 degrees and it went to the EGR system.
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Cargo Master
Joined: Dec 2004
Posts: 3,362
Likes: 22
From: Florence, SC
Well, I thought it was for controlling the canister purge for the EVAP system, but according to the '79 forums (I did a search) it seems on some models it is there for ignition timing. It seems that the distributor advance hooks to the middle port of the ported vacuum switch, the bottom port goes to MANIFOLD vacuum, and the top port goes to PORTED vacuum. Yes, I know my truck is an '85 (with A/C), but almost all of the emissions equipment is gone and I have had to start from scratch on the vacuum locations.
https://www.ford-trucks.com/forums/4...ingamajig.html
https://www.ford-trucks.com/forums/2...8-f-150-a.html
https://www.ford-trucks.com/forums/4...ingamajig.html
https://www.ford-trucks.com/forums/2...8-f-150-a.html
...the three port switch at the front was used to help cool the engine by advancing the timing and allowing the engine to increase rpm for better coolant flow.
This setup would give no vacuum advance when the engine was cold, normal vacuum advance at normal operating temperature, and manifold vacuum when the engine was overheating (the manifold vacuum would cause a higher idle, thereby cooling the engine off).
Cargo Master
Joined: Jan 2004
Posts: 2,512
Likes: 8
From: Cook Forest and Irwin PA
Its also caleld a 'TVS'( thermal vaccum switch). that one is for overheat conditions to very advance vacuum at all times to cool cylinder head temps. LMC does have it...
pull it out of the engine and look for a scribed number on the copper portion.
pull it out of the engine and look for a scribed number on the copper portion.
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