User811780 Posted December 25, 2023 Author Share Posted December 25, 2023 then you don't have an hvac truck. there should be no vacuum circuit to deal with nor is there a hot/cold diverter door to be broken. the fan switch should go from off at the bottom to high at the top. there it a lever with a cable driven damper to go from the floor to the defrost and a lever to a cable from cool to heat. the blower still has a resister with two coils and one direct to the blower Sorry, it does have ac, I’m just only concerned with heat. The controls look like this. Link to comment Share on other sites More sharing options...
BigBrother-84 Posted December 25, 2023 Share Posted December 25, 2023 Sorry, it does have ac, I’m just :nabble_anim_confused:only concerned with heat. The controls look like this. Do you mean that the fan flow isn't strong? I mean that the heat is good but fan doesn't push enough? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 25, 2023 Share Posted December 25, 2023 Pulled the hvac control and nothing was connected to the blower motor switch. Plugged it in and now it works. Although now the off position blows through floor vents *with a vacuum system* Default should be defrost. Id think you either have a stuck vacuum motor or a vent door that's off it's hinges. The vacuum troubleshooting section at the back of the EVTM might be helpful. https://www.garysgaragemahal.com/1981-evtm.html Check also vacuum systems under: Documentation/Vacuum Systems/ various topics Plus, there are quite a few threads about repairing vacuum leaks, the coffee can reservoir, and fixing the doors. Link to comment Share on other sites More sharing options...
Gary Lewis Posted December 25, 2023 Share Posted December 25, 2023 *with a vacuum system* Default should be defrost. Id think you either have a stuck vacuum motor or a vent door that's off it's hinges. The vacuum troubleshooting section at the back of the EVTM might be helpful. https://www.garysgaragemahal.com/1981-evtm.html Check also vacuum systems under: Documentation/Vacuum Systems/ various topics Plus, there are quite a few threads about repairing vacuum leaks, the coffee can reservoir, and fixing the doors. If there’s no vacuum to the system, like when the vacuum line under the hood is off or broken it’ll be in defrost. You can see the vacuum line, tee/check valve, reservoir, and line into the cab here: Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 25, 2023 Share Posted December 25, 2023 If there’s no vacuum to the system, like when the vacuum line under the hood is off or broken it’ll be in defrost. You can see the vacuum line, tee/check valve, reservoir, and line into the cab here: Keep in mind the 19A566 can is prone to rusting out on the bottom where condensation collects. Link to comment Share on other sites More sharing options...
Gary Lewis Posted December 25, 2023 Share Posted December 25, 2023 Keep in mind the 19A566 can is prone to rusting out on the bottom where condensation collects. Yep, and that kills the vacuum. Link to comment Share on other sites More sharing options...
grumpin Posted December 25, 2023 Share Posted December 25, 2023 Yep, and that kills the vacuum. I would also check the vacuum line to the transmission modulator. It's on the firewall junction. The modulators can leak and destroy that vacuum line. Link to comment Share on other sites More sharing options...
User811780 Posted December 25, 2023 Author Share Posted December 25, 2023 I would also check the vacuum line to the transmission modulator. It's on the firewall junction. The modulators can leak and destroy that vacuum line. Thanks for the help everyone, after cleaning all the vents and plugging in the blower switch (not sure how it was undone) everything seems to be working normally. The only problem I have now is the blower motor does not turn off when the lever is in the off position. Which isn’t that big of a deal. Merry Christmas! Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 25, 2023 Share Posted December 25, 2023 Thanks for the help everyone, after cleaning all the vents and plugging in the blower switch (not sure how it was undone) everything seems to be working normally. The only problem I have now is the blower motor does not turn off when the lever is in the off position. Which isn’t that big of a deal. Merry Christmas! You might have a look at component testing (pgs 100&101) https://www.garysgaragemahal.com/component-testing.html Link to comment Share on other sites More sharing options...
User811780 Posted December 25, 2023 Author Share Posted December 25, 2023 You might have a look at component testing (pgs 100&101) https://www.garysgaragemahal.com/component-testing.html Thank you Jim. That is very helpful! Link to comment Share on other sites More sharing options...
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