1985 Ford F150
Carbureted 302 V8, AOD
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.
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.
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.
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.
...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).