1988 300E Cruise control doesn't work.
 

Right now in my bay I have a 1988 300E That the cruise doesn't work but used too.

A little backstory.

Customer brought car in with a car that the cruise control worked but would cut out randomly. So I measured amp draw on the actuator (well within spec) so I ordered an amplifier (remanufactured programa brand). Installed amplifier, took it for a 15 mile spin and cruise worked flawlessy.

A couple of weeks later customer comes in a little irate, still complains of it cutting out randomly (would cut out and not work till the next day).

Took it for a spin. hit set/accell, car revved up and bam no cruise control. Wouldn't work at all.

I removed the actuator and found 2 teeth missing on the inside....no biggie, order an reman programa actuator from peach parts.

Hooked up actuator and still no cruise.

Here's what I went over so far.

Tested switch, all ohmed out ok. And then checked power out from the switch all good.

Tested continuity from actuator plug to amplifier plug, all good.

Tested reference resistor all good.

Tested hall effect sensor on back of cluster, had 60hz at 30mph at the X53/5 Junction and at the amplifier plug.

I have power at the switch and the amplifier plug.

Verified pin 8 brake like circuit is good. (good ground with no brakes, 12v with brakes applied).

Tested grounds, all ok.

I even called programa tech support. He told me it was vacuum related......

I must be missing something. Thanks!

PM member James Dean he's the resident expert on cruise control issues.

Ihad same problem on 91 300 e, bad actuator , tested all wiring good , finally changed cruise amplifier after getting 3 bad ones at pick your part , likely the cruise amp , ther is a member here that rebuilds them and tests them use him

James Dean is your mann

Just was browsing the forum at lunch here and saw this. Thanks for all the recommendations guys.

I'd be happy to help out if I can.

If you would like you can send me the actuator and amp and I'd be happy to give them a test, no charge. Drop me an email at JamesDean59@gmail.com and we can go from there.

The fact that they blamed the problem on vacuum is laughable. A red flag that they have no idea what they are talking about in your situation. Especially given that the all MB's after about 1980 were equipped with ELECTRIC powered cruise control.

The quality of their rebuilds, at least in the context of these cruise control units, leaves much to be desired.

Programma is garbage. BTDT

Thank you!, I will definitely take up your offer.

Yeah their tech suppport seemed like a joke...I kind of gave up and didn't bother arguing. Luckily the parts supplier that supplied me the parts will refund me if necessary. Also ironically the customer stopped by mad as hell (which I don't blame him, my boss hasn't been keeping him up to tabs on my progress with the car.

When removing the one amplifier the board slid out on me. It doesn't look like they exactly replace all the caps that can fail. Looks like just a few resistors and caps.

It will be interesting to see the outcome of all this.

Did you check the brake bulbs? If the correct 21W bulbs have been replaced with anything else it can burn up the cruise amp. I never stick an amp in one without at least checking the bulbs and about half of all bad amps I see will have wrong bulbs.

That's interesting, can you explain more?

Wrong bulbs = too much current = fried cruise amp.

Programa is garbage !! This is who you need to call, Peter at General Development Labs. He has been repairing the units for my shop since 1995 & I have never had a issue with one of his actuators or control units. 805 772 5127
Howard