A/C and RPM

[g_man1972]

Hello all,

As of sunday I will be the proud owner of a 92 super exceed! Very excited and I can't wait to get my hands on her.

One quick question, when I was testing out the A/C the RPMs went up quite a bit, I didn't note exactly but I would say around 1500 give or take. No big deal, but what I was curious about was that after a few minutes they dropped down to normal again for a bit then increased to ~1500 again. I am used to rpm increases when the ac is on, but have never experienced it dropping, and then increasing by its self when the controls aren't touched, ie no settings changed.

I'll post a picture of two once I get her home.

Cheers

[BCDelica]

Welcome and Congrat's

I had to adjust the vacuum advance on my Deli to actually idle up when the AC is turned on, and the manual said to set it so the idle revs came up to 1500rpm when the AC was turn on. Sounds to me like some one set your Deli up properly.

#1 red arrow points to the AC vacuum advance.

From - http://www.delica.ca/forum/injection-pu ... s-684.html
Cheers,
Kev

[g_man1972]

Okay excellent.

Is it normal for the RPM to drop though? I figured that it should remain constant as long as the engine load and A/C setting remain unchanged.

Take care,

[Schwa]

The A/C compressor cycles on and off when your switch the A/C on, at least mine does.

[g_man1972]

Okay cool, nothing to fear then.

24 hours and impatiently counting:-)

[EnviroImports.com]

Yes thats perfectly normal, when the AC comes on the engine has to put out more power, if you park and turn it on , you will hear the ac "click" off when the rpm's drop. Its a good thing.
Noel

[Schwa]

Also, you'll notice it click on more often and stay on longer when you have the rear A/C turned on as well since there's more heat to pump out of the van.

[g_man1972]

Thanks for putting my mind at ease. what I just figured out is that this is my first diesel and the reason it seemed so harsh is that I am not used to the sound of the engine. with the doors open and at idle the jump from 650 RPM to 1500 was very noticable and I think thats what surprised me.

Well the deal is done and I am happily booting around in my new ride. I have not enjoyed driving a vehicle this much since the first time I drove solo after getting my licence all those years ago. And the looks from people are great, I had two 4x4 guys giving her a good once over doing the nod the whole time. Keep an eye out for a dark green/light grey super exceed driving around east van and richmond, happy to say hello.

Cheerio

[jrman]

Ok - so now after reading this post, I'm concerned for the opposite reason. I hear the AC pump kick in - and kick off - but I have very little to no change in RPM. I do notice that is clicks on and off more frequently than any other AC vehicle I've had. Recommendations? Should I adjust the vaccuum advance to allow for higher RPM? It is ok to leave "as-is". Is this one of the "6 of those / half dozen of the other" situations? Appreciate the input.

[jrman]

I just noticed from another post where Green1 is looking for an AC low pressure switch - and there was a comment that frequent cycling of the compressor "can" mean low on refrigerant. I reconfirmed this evening that my RPM in fact drops slightly when the compressor clicks on, I can sense the greater load on the engine, and the RPM's come up slightly (50 rpm maybe - virtually negligible) when the compressor cycles off - and I'm getting quite cool air so at least it's working ok. Anyway - just my system seems to buck the trend, and just hoping it's not leading to a problem.

[Schwa]

Unless the mechanism that turns up the fuel flow is not functioning, you should be able to adjust it so that it brings the RPMs up when it kicks in. Check for movement around the fuel pump when the AC kicks in.

[EnviroImports.com]

Please be carefull if you dont feel confident about adjusting your settings if you dont feel VERY Very confident in what your doing, you dont want to mess up your injection pump, If your seriously worried about it then try or take it to a trustworthy mechanic, ya, I know they are few and far between, but ask around for who is good and bad.
But Im very mechanical, I build custom 4x4's and I dont touch injection pumps and things like that. its the heart of your system and can be easily Fubar'd
Just my $.02 worth
Noel

[Schwa]

Here's a short clip of mine, I'm switching the A/C on and off but the same thing happens when it does it by itself.

http://www.youtube.com/watch?v=ZIXLuIwGEA0

The mechanism is an electrically controlled vacuum servo, so the problem could be with the electrical side, the vacuum part or the mechanical linkage to the fuel pump assembly.

[jrman]

Erick,
Very cool vid - makes diag so much easier. Will take a look shortly - even though AC season is gonzo here in Van it seems. Funny thing - air is nice and cool - but I'm interested to see if my "under the hood" reaction is the same as yrs when the AC Compressor is working. Will advise.
Tks.