ABS light at 78 MPH? & R134a question

[SteveD2]

My car is a 1991 Mazda 626 LX (Auto) (Non-Turbo). I just got it 2-3 weeks ago. It has 4 new tires. Everything appears fine.

The only problem is around 65 MPH, the car started shaking a bit (feels like the wheels not the engine nor transmission). Then as soon as I hit 78 MPH, the ABS light came on and stayed on until the car is shut off. When I turn the key to on and start it, all the self checks are ok. Then all the lights went off until I reach 78 MPH again.

I don't know what the deal is. I checked the owner's manual and all it says is if the light is gone at starting, the ABS is functioning ok.

So, is my ABS something wrong or is it a feature thing? First time I have a car with ABS and it is getting confusing.

Another question is the car was converted to R134a (professionally by previous owner) about 6 months ago. Right now, it is not that cold at all. It's only as cold as my R12 system almost running out after 12 years. Are R134a all like that? or should I be recharging it?

Please help. TIA.

 

[Ugly3]

General rule: if the steering wheel is shaking at high speed it is the front wheels out of balance, if the drivers seat seems to be vibrating it is the rear wheels out of balance.

The ABS is connected to the wheels with a plastic connector, could be shaking loose and turning the light on.

As for A/C - my experience has been that 134A is just as cold as F12. My 134A output temp is 45F with both the front and rear blowers going full tilt with the outside air at 90F. Freeze your butt off!

 

[Chris142]

When retrofitting an older system to R134a The charge must be exact. + or - an ounce!

Any farther off and it won't cool correctly.

Some cars take a retrofit better than others. You could be slightly overcharged or undercharged
You may have other problems such as a worn compressor or clogged/bent condensor fins.