No matter what setting the climate control is on, the heater is stuck on and blower motor never engages or blows. How would I go about fixing this? I am completely clueless.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Does air only come through the defrost vents? If so, there's no power to the PBU. Check the ACC fuse. If it's good, maybe the unfused aux pump seized and took out the PBU.

Sixto
98 E320s sedan and wagon

Air doesn't blow anywhere whatsoever.

__________________
1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Start with the basics. The default operating mode of the system is "heat" so that if the system takes a dump it will still run in heat just from the air being forced through from outside.

The monovalve must be energized to close. If it doesn't receive power, you get full heat. They also tend to bind up over time staying open even if commanded to close.

Check Fuse #5. It powers just about everything ACC related. If it is blown the monovalve will be open and the pushbutton unit will be dead. You also won't hear the aspirator motor behind the glovebox whirring.

Depending on when your car was built, it'll have a 25A fuse in #16 or it'll have an external fuseholder next to the fuse box with a strip fuse in it for the fan. If the older style with a fuse in #16, they're prone to melting and failing. The strip fuse in the external holder is prone to cracks, it is the same type fuse used in the fusebox for the rear defrost.

Check the fuses mentioned and report back.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

The fuses are intact

__________________
1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

When you turn the key to preglow and the buzzer stops, do you hear the aspirator motor whirring behind the glovebox? It should be on regardless of the function of the HVAC system. Even when it is "off" it is still running with the key on.

The next thing I'd suspect would be the pushbutton unit. Since none of the functions work, including blower, that would be getting the stink-eye from me. Mine kept dropping the fan out when hitting a bump in the road, fiddle with the fan switch and it would come back on. When I took it apart, nearly every switch in the thing had broken solder joints.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

No, it is dead silent in pre glow.

How hard is it to get the push botton unit out?

__________________
1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

If you have access to a multimeter, go test voltage from Fuse 5 to the engine block with the key on. Rule out an ignition switch problem first.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Just tested it, no voltage at all.

__________________
1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

How about 6, 7, or 8? They are all switched off the same terminal on the ignition switch.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

No power on any of them.

__________________
1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Start you engine and turn your blower to max position. Ever so lightly move your key left then right (repeating) without moving out of #2 position and see if the blower engages. If it does the contacts on the ignition are worn/dirty.

__________________
BENZ THERE DONE THAThttp://www.peachparts.com/shopforum/...c/progress.gif
15 VW Passat TDI
00 E420
98 E300 DT
97 E420 Donor Car - NEED PARTS? PM ME!
97 S500
97 E300D
86 Holden Jackaroo Turbo D
86 300SDL
(o\|/o)

The blower never engaged.

__________________
1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Dang, I would have bet a donut on that too.

__________________
BENZ THERE DONE THAThttp://www.peachparts.com/shopforum/...c/progress.gif
15 VW Passat TDI
00 E420
98 E300 DT
97 E420 Donor Car - NEED PARTS? PM ME!
97 S500
97 E300D
86 Holden Jackaroo Turbo D
86 300SDL
(o\|/o)

I'm with TX, key switch is the next suspect.

Sixto
98 E320s sedan and wagon