Hello I'm new to this forum. I have a 1988 ford f250 4x4 with the 460 or 7.5l engine. I just installed a used engine and it took me about to months to finis it and get it running. with that being said I must have for got where some vacuum lines go and come from. so here is my ? my heater control worked perfectly before I started and now it will not switch from defrost to vent to floor. I know I have got a vacuum problem some where. So if anyone can tell me where I can get vacuum diagrams I would really appreciate it.
The best answer is the correct year Electrical & Vacuum Troubleshooting Manual for F150-250-350 and Bronco.
(this is a Ford manual usually available from Helm Inc. or used on Ebay)
My carbureted '87 460 does not have a vacuum reservoir for climate control, but if your EFI version does have a plastic ball or coffee can on the passenger fender then you know where to start looking.
On my truck that vacuum line comes from a plastic tee on the firewall (above the passenger side valve cover) to an inline check valve and goes into the cab just below the heater hose connection on the firewall.
These hard plastic lines get very brittle.
The easiest way to repair them is to purchase bulk rubber line that slips over tightly.
Sorry, I do not have the correct EVTM for your EFI truck.