Troubleshooting Tronic's AMC 1.5 & 1.2bDSMhb

[petteriu]

Built these years ago and already back then verified their basic functions without motors. Just recently decided to revive this project and continued where i left off.

Everything still seems to work as planned; direction indicator LEDs following pot rotation and LCD display showing numeric values and multimeter hooked up to either output i get -12,7V...12,7V on both motor outputs. But when i hook up actual wiper motors results change and are not so good.

I have verified functionality and speed of motors by running them directly off car battery. Using same car battery to power up H-Bridge i get sluggish movement to both directions on one motor (although accelerating slowly, voltage starting from ~4V) while other motor only turns one direction (but with ~12V). There seems to be a slight difference in speed if only one motor is hooked up, but not drastic. Having both motors connected and operated at the same time surely seem to effect performance, moving one halts other, just as if there is a serious lack of power.

Using search, I noticed similar symptoms described in few other messages. In one of them having motor structure connected to terminal was bad, but my motors are not bolted to anything yet and they work ok directly off battery, so could that still be a problem ?
Other than that i would not want to just go ahead and start changing components randomly just to sure, i would like replace only something that needs to be replaced.

So i'm unsure of what look for and check next !