jumpy RPM when fan on

[petiec]

Now and then when i use my fan my RPM needle jumps and this only happens when at a complete stop.It only happens when the fan speed is on two or higher?The car is an 95 4 cylinder 5 spd.

[_-Night-Shade-_]

-_-''

It's normal. When you turn on an electric load (fan, defrost, etc.) the idle will go up to generate more power for the alternator to compensate. You don't notice it when driving cause the RPMs are significantly higher and are sufficient enough.

[petiec]

l understand about the electrical load when using fan,def. etc. my problem is that the RPM wont idle steady,the RPM gauge goes from 1100 to 600 and then back and forth,and it doesnt always happen.

[_-Night-Shade-_]

That makes no sense, that's usually a symptom of a vaccuum leak somewhere, but if that's the case then the fan should have no effect on that.

[umcamara]

That makes no sense, that's usually a symptom of a vaccuum leak somewhere, but if that's the case then the fan should have no effect on that.

It makes complete sense, it's happened to me. Not sure what the cause of it was, but I (properly) raised my idle a touch by entering diagnostic mode, etc, and the jumping idle issue stopped. I have a feeling it has something to do with the IAC valve (Idle air control valve)

[Ryan]

A few guys have had the issue of the idle not deciding where to sit when electrical load is applied. I, personally, think its a glitch in the original ECM programming. Just raise your idle a bit, and it will go away.

[wytbishop]

My car does that exact same thing when the coolant level gets a bit low which is of course a temp sensor problem in my case. If it wasn't for the fact that you say it only happens with the fan on I would say check your coolant level. Check it just to be sure.

My guess would be bad grounds in your case. Remove the ground wires, clean the ends, clean the parts that they connect to and reinstall. Also the #8 wire that goes from the battery negative terminal to the firewall, the output wire from the alternator and the positive terminal on the starter...clean them as well.

[_-Night-Shade-_]

That makes no sense, that's usually a symptom of a vaccuum leak somewhere, but if that's the case then the fan should have no effect on that.

It makes complete sense, it's happened to me. Not sure what the cause of it was, but I (properly) raised my idle a touch by entering diagnostic mode, etc, and the jumping idle issue stopped. I have a feeling it has something to do with the IAC valve (Idle air control valve)

Just cause it has happened to you doesn't mean it makes sense. It means you just had a similar problem without figuring out what was causing it.

[umcamara]

That makes no sense, that's usually a symptom of a vaccuum leak somewhere, but if that's the case then the fan should have no effect on that.

It makes complete sense, it's happened to me. Not sure what the cause of it was, but I (properly) raised my idle a touch by entering diagnostic mode, etc, and the jumping idle issue stopped. I have a feeling it has something to do with the IAC valve (Idle air control valve)

Just cause it has happened to you doesn't mean it makes sense. It means you just had a similar problem without figuring out what was causing it.

What on earth are you talking about? I said that as the OP said, my idle used to bounce around after turning the fan on. What doesn't make sense about that? Just because I didn't quite figure out the source of the problem doesn't mean the problem didn't exist. It makes complete sense that others may experience the same issue and not know what the cause was.

[_-Night-Shade-_]

What on earth are you talking about? I said that as the OP said, my idle used to bounce around after turning the fan on. What doesn't make sense about that? Just because I didn't quite figure out the source of the problem doesn't mean the problem didn't exist. It makes complete sense that others may experience the same issue and not know what the cause was.

That's not what I was talking about. I was referring to the SYMPTOMS which don't make sense for this particular issue. Jeez that's one thing I hate about this forum sometimes, instead of trying to help people out sometimes people just bash other people's attempts to troubleshoot a problem. VERY helpful (sarcasm)

[umcamara]

What on earth are you talking about? I said that as the OP said, my idle used to bounce around after turning the fan on. What doesn't make sense about that? Just because I didn't quite figure out the source of the problem doesn't mean the problem didn't exist. It makes complete sense that others may experience the same issue and not know what the cause was.

That's not what I was talking about. I was referring to the SYMPTOMS which don't make sense for this particular issue. Jeez that's one thing I hate about this forum sometimes, instead of trying to help people out sometimes people just bash other people's attempts to troubleshoot a problem. VERY helpful (sarcasm)

Who's bashing? I simply stated that it makes complete sense. Don't take things so personally dude. I don't bash anybody on here.

[_-Night-Shade-_]

Just to be clear: the symptoms he was describing were a lot like an intake leak or low coolant or whatever, hence I said it didn't make sense that the fan would have anything to do with it.

[umcamara]

To me it just came across as if you were saying that his problem didn't make sense, and that clearly he was an idiot and the problem didn't exist.

Simple mis-understanding. No harm no foul.

[petiec]

Thanks umcamara,l thought the same thing for a second but anways l checked the coolant level it was fine,the Temp. sensor l replaced new from mazda dealer and then had them adjust the idle.The ground on the battery is cleaned but havent got to the rest of the ground connections.Just a thought see what you guys think can it be a bad HVAC or a relay on the blower motor? Funny how it never happens on first speed only second and third. Thanks for all the positive help guys hope l can get this problem resolved,Any more suggestions from my fellow MX-3 guys would be greatly appreciated