Dash A/C and step relationship

[saflyer]

There is a 7.5a fuse in the forward run bay labeled Step/ISO Sense. It burns out. I found it because there are two things I have problems with that are both related to this fuse. It apparently has something to do with the ignition switch. It turns out the dash A/C was blowing through the windshield vents regardless of what position the A/C selector was in. At about the same time the entry steps stopped retracting when the door was shut with the ignition switch in the on position. Thanks to one of you who sent a wiring diagram the dash A/C, entry step and ignition have some common wiring. 

I don’t know where the problem is. I don’t think it’s the step motor even though the fuse blows if I close the door with the ignition switch on without any movement of the step motor. But the steps retract properly when their switch is in storage mode and the door is closed regardless of ignition switch position. I thought the dash A/C wasn’t causing the problem because using it didn’t seem to blow the fuse. A good fuse allowed the A/C doors to move to the proper position based on A/C mode selected. (It turns out they default to windshield defrost position with no power.) But that idea didn’t hold up as yesterday I operated the A/C only and when I switched modes the fuse blew.

So that leaves the ignition switch or wiring itself, am I right? This is probably beyond my capabilities but maybe someone has an idea for an easy thing to check.

Thanks,         
Ed             
‘05 HR Ambassador

[saflyer]

I just put a new fuse in, disconnected the A/C vacuum pump, turned the ignition switch on and tried the entry door. The steps operated properly several times. Reconnected the vacuum pump, turned the A/C control to dash fan and the fuse blew. So I’d be willing to replace the vacuum pump but part number E3HT-2A451-BA is obsolete. Ford parts dept. is of no use. Online options do not have this part number but would probably work except for the 12v connections. Mine are blade style. The pictures of the replacements show a cannon plug type or something to that effect. Don’t know if I could adapt my plugs. They are in the $39-55 range. Veurinks seems to offer the exact part that I removed but at $150! Any suggestions?

Ed

[Dear LaserWorks]

Sounds like what happened to us (2000 Diplomat). We used a part off Amazon with a different connector, so I made my own wiring to the new pump which has worked great for at least 12 months now. I also bench tested the old pump & it was clear the motor was shot, made odd noise & blew a fuse when I put my finger over the hole so it would attempt to draw a vacuum.

https://www.amazon.com/gp/product/B001KQF6PC/

Edited October 18, 2021 by Dear LaserWorks

[Dr4Film]

Ed, there are plenty of electric vacuum pumps to choose from. There may even be one listed in the Monacoers Parts List. Just buy a new one, install it and you should be good to go.

[saflyer]

5 hours ago, Dr4Film said:

Ed, there are plenty of electric vacuum pumps to choose from. There may even be one listed in the Monacoers Parts List. Just buy a new one, install it and you should be good to go.

I don’t know that it is that simple. I found a Dorman 904-214 online but it has a 4 wire female connector. Mine has only two wires so I wonder what function the other two wires serve. My fist thought is the vacuum sensing in my pump is internal to it while the Dorman one might get its sensing from an external source. I don’t know. I can get a 4 wire male connector and just use two of the wires but wonder if that will work.

I can’t find the Monacoers parts list. I found “Store” but it just returns a blank page.

Edited October 19, 2021 by saflyer

[Dr4Film]

I'd bet that your local NAPA store would have exactly what you need or could get it. Just remove what you have and take it with you.

[saflyer]

On 10/19/2021 at 11:31 AM, Dr4Film said:

I'd bet that your local NAPA store would have exactly what you need or could get it. Just remove what you have and take it with you.

The exact part number is discontinued by Ford. Everything I found online had a different wiring connection. With some research and a big leap of faith I found a Dorman unit and installed it. Works so far. The vacuum pump seems to be where the problem was.