Electrical gremlins...

[Daryl]

1. ABS idiot light always comes on, usually after driving a short time
2. AC/vent/floor (etc) selector only blows out of the windshield defroster vents, regardless of which function I select.

3. AC doesn’t blow cold... at all! Should I try AC Pro or similar and risk blowing up my compressor(which is likely shot anyway after 25 years!)? 2/70 air works sometimes but it’s getting hot and that all black leather interior is unforgiving!

 

[Werecow]

I have a solution for 2, check and see if the vacuum hose at the firewall is connected.. I can't remember the color, but this is what controls the flappers inside when you move the selector from vent to dash to floor... If it's not got any vacuum to it, it will only blow out the vent to the windshield...

 

[evilcw311]

The vacuum line is a small black plastic line about 1/8”. It runs from a vacuum tee in the drivers fender over towards the passenger side of the firewall. It’s notorious for dry rotting and braking into pieces.

The ac system you should get checked out. If you don’t have a proper set of manifold gauges it’s hard to say what the issue is. You can check things like seeing if the compressor is even kicking on but outside of that you need to read pressures on high and low sides.


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[ttocs]

the abs light coming on is probably a signal that your brake fluid reservoir is low. Check the level, refill if needed and then check around the 4 corners for leaking brake lines.

 

[ttocs]

I have a solution for 2, check and see if the vacuum hose at the firewall is connected.. I can't remember the color, but this is what controls the flappers inside when you move the selector from vent to dash to floor... If it's not got any vacuum to it, it will only blow out the vent to the windshield...

black vac line comes out on the passenger side firewall by the AC lines. It goes over the top of the motor to the vac tree and comes disconnected above the motor. You can get a little larger piece of vac line to slide over the two ends to reconnect them. This could also be your problem with the ac not blowing cold as if you direct it to the windshield it heats up before it gets to you.

 

[Daryl]

This one? The one with the white plastic T-junction?

 

[evilcw311]

View attachment 5941
This one? The one with the white plastic T-junction?

No. That’s the Evap purge canister


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[Daryl]

No. That’s the Evap purge canister


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Rats! It was the first obvious 1/8” line that I could see. Is the line I’m looking for somewhere in the picture at least?!

 

[evilcw311]

Rats! It was the first obvious 1/8” line that I could see. Is the line I’m looking for somewhere in the picture at least?!

It’s a very tiny plastic line. Not rubber. Runs from the driver side fender to the passenger side of the firewall.


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[Daryl]

Aha! Could it be this lil beauty that at some point got snipped off?

 

[ttocs]

probably.

 

[evilcw311]

View attachment 5942
Aha! Could it be this lil beauty that at some point got snipped off?

That’s the one!!!!!!! There should be a small plastic line from there over the the firewall. They snap off easily


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[Daryl]

Sweet! Now that I found it, I just have to source one! When I go looking, is it just called “AC line”?

 

[evilcw311]

Sweet! Now that I found it, I just have to source one! When I go looking, is it just called “AC line”?

You won’t find that nor would you want to. You need to find a small vacuum line thy will fit on that tee and go from there.


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[Daryl]

NAPA here I come! My guys who work at my neighborhood NAPA are awesome at finding and sourcing parts. Also helps that one of them has a Mustang GT and is an enthusiast!

 

[Daryl]

Werecow,
Thanks!! My guys at the local NAPA were able to piece together some in-line couplers and vac line that “should” work. Will find out tomorrow morning when I dive into this little project.

Fingers crossed....

 

[MyLittlePony]

1) check brake fluid level, as suggested. If full, and you don’t think it has ever been serviced in its life, it may be time to flush it.

2) If the parts you throw at it doesn’t fix it, pull the HVAC unit. The radio bezel will need to be removed first. This happened to me. There are tiny rubber hoses that connect to the unit itself. One had popped off. Probably happened during radio installation.

3) does the compressor spin at all? Could be seized. This also happened to mine once. The other times it was because there was a leak. If refrigerant is too low, the computer will prevent the compressor from engaging to prevent damage. It won’t engage until it thinks there’s refrigerant. And the only way to get it to accept more, refilling it, is to get it to engage, meaning you have to short the sensor. But we’ll get to that later.

 

[Daryl]

RESULT!!!
I can scratch off numbers 2 and 3 from the list! I replaced the missing vacuum line with two straight connectors and just under 3’ of hose, sealed the connection points, secured the new line out of harms way along the firewall with a couple of zip ties... and viola, it works!!

The only selector that doesn’t is the “mix” (floor & vent) option. But all others function as they should AND the A/C is blowing cold!

Can’t thank you ALL enough for your input, suggestions and guidance through this project. Definitely could not have done it otherwise and would have probably taken it to an A/C shop for who knows how much in repairs?
All in, I spent $6.38!!!

You all are awesome and I can’t tell you how good this makes me feel (1) to get your help and then actually successfully fix it!; and (2) to getting my car that much closer to running and functioning how it should and how I want it to.

Thanks again to everyone who chimed in and helped!..... see you at my next Thread, which will likely be sooner rather than later, right, knowing me?!!

 

[Daryl]

Spoke too soon! The A/C “was” or “seemed to be” blowing cold when I first started the car up to see if my vacuum line fix worked. But after driving it and engine warm, the A/C doesn’t blow cold.
A/C Pro time???

 

[RAU03MACH]

Spoke too soon! The A/C “was” or “seemed to be” blowing cold when I first started the car up to see if my vacuum line fix worked. But after driving it and engine warm, the A/C doesn’t blow cold.
A/C Pro time???

Reach down on the accumulator line
Is it cold when running
Then touch the ac line cold side on the compressor see if cold, if not
The orfic tube is plugged up