Today's Mystery Machine mysteries!

[Eric1971]

Previously on "The Mystery Machine"... I replaced/repaired the EATC controller and got my AC back and all was good in the world... for a few weeks.

Then, I went to pick up my daughter from school one day and the main AC blower was not coming on. I know the rest of the system is ok because I put a test light on the compressor clutch so I could tell when it was engaged from inside. Said light was on when expected and the rear blower was blowing cold. Searched the forum, tried to find the blower relay with no luck, checked the 2-wire connector on the blower motor and the blower started working again.

Today it wasn't working again, so I again tried to find the blower relay, but what I see doesn't match what's in my manual. Before messing with the connector again I tapped the blower casing with my magical screwdriver and presto on came the fan!

So...

- Where the heck is the blower motor relay?! All I could find was this (see red in pics) one similar bus in the far front/passenger corner under the hood in front of the air filter, but it doesn't exactly match what's in my manual and there's only one relay in it that is apparently NOT the blower relay. I'm wondering if someone has bypassed the blower relay at some point in the past. Is that something people do? I see a couple of wire crimp connectors near the blower that might be from a bypass.

- What is this empty round connector in these pics? That's as mysterious as the one mandatory light switch in each house that no one knows what it does!

- Do these symptoms on the blower sound familiar? I was going to check the blower connector with my multimeter but then the blower came on. I'll try to get it next time!

- Any other thoughts or suggestions?

Thanks!

 

[J_C]

I'd imagine your motor has a bad spot on the commutator or brushes are shot and this is why tapping it worked.

Using a multimeter to check power at the connector is a great idea. If no power, clearly something upstream is at fault, though it could be at 12V no load, but the relay is high resistance and dropping voltage under load so it is good to test it with needle probes while plugged into the fan if possible.

I don't know where the relay is on a '95. On my '98 it's in the under-hood power distribution box but I'm sure that box changed from '95 to '98.

 

[Eric1971]

I think J_C wins. I went out, started the truck and AC, no blower again. Tested the motor connection at 14.4v. Gave the motor a solid tap with my pliers and there it starts! So, I will have to replace the blower motor it seems. I noticed the air tube was disconnected at the non-motor end. I'm wondering how long it's been that way and if lack of cool air + hot motor + Georgia summer heat = mostly dead motor.

There are still prizes available for answers to:
- Where is my blower relay?!
and
- WTH is that round plug connector?!

Thanks for playing!

 

[Eric1971]

I'm still trying to figure out the blower relay location and ID this round connector if anyone can please help. Thanks!

Blower is replaced and working great now.

 

[Eric1971]

Mystery #2 solved, maybe. That red panel IS the blower relay location which I verified by pulling the one relay which is the front washer pump. It looks like the halves of that panel are swapped. Looking at the EATC wiring diagrams, I don't see any relays in the blower circuit, so maybe there are none and never have been.

Still no clue on the round connector. I can't find anything that is unplugged. Maybe it's for something I don't have like 4x4...

 

[96eb96]

Many years ago I bought the expensive EATC module from Ford. A tech sold me the part, and he said you should replace the blower, and its fine to get one from a parts store. The blower motor can wear out and take the module with it, because it draws too much current. He said many fail because of a bad motor. Maybe an extra amp or two is enough to fry it.

 

[Eric1971]

Hopefully, I'm all set then now that both are fixed. The EATC controller had a bad solder on a relay, maybe due to the fan drawing too much current, as you said.

I see your Exp is like mine but '96 and 4x4. Do you have that round connector by your air cleaner, and if so, is it connected to anything? Thanks!

Many years ago I bought the expensive EATC module from Ford. A tech sold me the part, and he said you should replace the blower, and its fine to get one from a parts store. The blower motor can wear out and take the module with it, because it draws too much current. He said many fail because of a bad motor. Maybe an extra amp or two is enough to fry it.

 

[96eb96]

Hopefully, I'm all set then now that both are fixed. The EATC controller had a bad solder on a relay, maybe due to the fan drawing too much current, as you said.

I see your Exp is like mine but '96 and 4x4. Do you have that round connector by your air cleaner, and if so, is it connected to anything? Thanks!

The 4x4 system is around there, so your 4x2 may be a connector to nowhere.
On 95-96 there is a complicated front axle disconnect. It allows for a true 2wd mode. After that, they had full time AWD or Electronic 4x4.